FXUS66 KSEW 261111

AFDSEW



AREA FORECAST DISCUSSION

NATIONAL WEATHER SERVICE SEATTLE WA

410 AM PDT FRI APR 26 2013



.SYNOPSIS...HIGH PRESSURE ALOFT WILL WEAKEN TODAY. ONSHORE FLOW WILL 

STRENGTHEN WITH MORNING CLOUDS ALONG THE COAST AND AREAS OF THE 

INTERIOR. A FRONT WILL MOVE INTO THE AREA FROM THE NORTHWEST 

SATURDAY AFTERNOON AND EVENING. A MUCH STRONGER SYSTEM WILL ARRIVE 

LATE SUNDAY. THIS SYSTEM COULD BRING LOCALLY HEAVY SNOW TO SOME OF 

THE CASCADE PASSES SUNDAY NIGHT AND MONDAY.



&&



.SHORT TERM...SATELLITE IMAGERY SHOWS LOW CLOUDS ALONG THE 

COAST...DOWN THE STRAIT OF JUAN DE FUCA AND THROUGH THE CHEHALIS GAP 

INTO THE SOUTH SOUND. SURFACE GRADIENTS HAVE GONE ONSHORE WITH THE 

KUIL-KBLI AND THE KHQM-KSEA GRADIENTS PEAKING OUT AROUND PLUS 2 MB 

THURSDAY EVENING. TEMPERATURES AT 3 AM ARE MOSTLY IN THE 40S.



EXPERIMENTAL GOES FOG DEPTH IMAGERY ESTIMATES TOPS OF THE STRATUS 

BETWEEN 1200 AND 1500 FEET THIS MORNING. WITH THE WEAK ONSHORE 

GRADIENTS AND THE RELATIVELY SHALLOW MARINE LAYER EXPECT THE STRATUS 

TO BURN BACK TO THE COAST THIS MORNING. TEMPERATURES ALOFT ARE STILL 

WARM WITH THE 850 MB TEMPERATURES STILL UP AROUND PLUS 8C SO ONCE 

THE SUN COMES OUT LATER THIS MORNING TEMPERATURES WILL WARM UP 

QUICKLY. THE WEAK MARINE PUSH WILL RESULT IN MAX TEMPERATURES A 

LITTLE COOLER TODAY...UP TO 5 DEGREES COOLER THAN THURSDAY...WITH 

MOST PLACES IN THE 60S. THE EXCEPT WILL BE THE COAST WHERE THE CLOUD 

COVER WILL HANG IN ALL DAY LEAVING HIGH TEMPERATURES IN THE MID 50S. 



ONSHORE GRADIENTS PICKING UP AGAIN TONIGHT WITH THE STRATUS MOVING 

BACK INLAND OVERNIGHT. WEAK COLD FRONT DROPPING DOWN ALONG THE 

BRITISH COLUMBIA COAST STILL NORTHWEST OF THE AREA AT 12Z. 



COLD FRONT SLOWLY MOVING INTO THE AREA SATURDAY WITH THE FRONT 

DISSIPATING OVER WESTERN WASHINGTON SATURDAY EVENING. HIGHEST POPS 

ASSOCIATED WITH THE FRONT OVER THE NORTHWEST INTERIOR AND NORTH 

CASCADES WHILE SOUTH OF SEATTLE JUST A CHANCE OF RAIN IN THE 

AFTERNOON AND EVENING HOURS. 



AFTER A BRIEF BREAK LATE SATURDAY NIGHT INTO SUNDAY MORNING A 

STRONGER SYSTEM ASSOCIATED WITH A 150 KNOT PLUS JET WILL APPROACH 

THE AREA ON SUNDAY AFTERNOON. WITH THE STRONG JET MODELS ARE HAVING 

A LITTLE DIFFICULTLY WITH THE TIMING OF THIS FEATURE. THE NAM IS THE 

FASTER OF THE MODELS WITH THE ONSET OF THE PRECIPITATION SUNDAY 

AFTERNOON. THE GFS AND ECMWF ARE A LITTLE SLOWER WITH THE 

PRECIPITATION HOLDING OFF UNTIL SUNDAY EVENING. GIVEN THE STRONG 

ZONAL FLOW WILL GO WITH THE FASTER NAM TIMING. 



FRONT MOVING THROUGH THE AREA LATE SUNDAY NIGHT. LOCALLY HEAVY 

PRECIPITATION IS POSSIBLE ALONG THE COAST AND ON THE WEST FACING 

SLOPES OF THE OLYMPICS AND CASCADES. SNOW LEVELS INITIALLY ARE ABOVE 

THE PASS LEVELS BUT DROP QUICKLY WITH THE FRONT. STILL PLENTY OF 

PRECIPITATION WITH AND BEHIND FRONT LATE SUNDAY NIGHT INTO MONDAY 

WHICH WOULD RESULT IN SIGNIFICANT NEW SNOW ACCUMULATIONS IN THE 

MOUNTAINS WITH THE SNOW LEVEL LOWERING BELOW ALL OF THE PASSES.



.LONG TERM...GOOD AGREEMENT IN THE EXTENDED MODEL SOLUTIONS EARLY ON 

WITH A POST FRONT TROUGH OVER THE AREA ON MONDAY KEEPING SHOWERS IN 

THE FORECAST. MODEL SOLUTION DIVERGE ON TUESDAY WITH THE ECMWF 

KEEPING SOME TROUGHINESS IN THE AREA WHILE THE GFS STARTS BUILDING A 

RIDGE. WITH THE UNCERTAINTY WILL KEEP CHANCE POPS IN THE FORECAST. 

GOOD AGREEMENT ON DAY 6 AND 7 WITH AN UPPER LEVEL RIDGE OVER THE 

AREA. GFS IS A LITTLE STRONGER WITH THE RIDGING WITH 500 MB HEIGHTS 

APPROACHING 580 DM. IF THIS VERIFIES NEXT WEDNESDAY AND THURSDAY 

COULD SURPASS THE LAST COUPLE OF DAYS FOR THE WARMEST DAYS OF THE 

YEAR SO FAR. FELTON 



&&



.HYDROLOGY...

FLOODING IS NOT EXPECTED THE NEXT 7 DAYS.



&&



.AVIATION...AN UPPER LEVEL RIDGE OVER THE AREA WILL CONTINUE TO 

WEAKEN AND FLATTEN THROUGH TONIGHT WITH WESTERLY FLOW ALOFT. LOW 

LEVEL ONSHORE FLOW WILL PREVAIL TODAY...EASING A BIT TONIGHT. THE 

AIR MASS IS STABLE WITH COASTAL STRATUS EXTENDING PARTIALLY INLAND 

DOWN THE STRAIT OF JUAN DE FUCA AND THROUGH THE CHEHALIS GAP EARLY 

THIS MORNING. 



STRATUS SHOULD REACH MOST OF PUGET SOUND BY DAYBREAK BUT IT WILL BE 

A FAIRLY SHALLOW MARINE LAYER AND IS EXPECTED TO SCATTER OUT BY LATE 

MORNING OVER MOST OF THE AREA. STRATUS SHOULD SPREAD BACK INLAND 

TONIGHT UNDER THE INFLUENCE OF CONTINUED ONSHORE FLOW.



KSEA...STRATUS EXPECTED TO REACH THE TERMINAL AROUND DAYBREAK...LAST 

FOR A FEW HOURS...THEN BURN OFF LATE IN THE MORNING. TONIGHT SHOULD 

SEE A REPEAT OF THIS SCENARIO WITH THE STRATUS PERHAPS DEVELOPING A 

BIT EARLIER. LIGHT WIND EARLY THIS MORNING...BECOMING SOUTHWEST 6-10 

KNOTS TODAY. SCHNEIDER



&&



.MARINE...MODERATE ONSHORE FLOW WILL PREVAIL TODAY...EASING A BIT 

TONIGHT AS A FRONT APPROACHES FROM THE WEST. SMALL CRAFT ADVISORY 

WEST WINDS IN THE STRAIT EARLY THIS MORNING ARE EXPECTED TO EASE 

SLIGHTLY LATER THIS MORNING AND THEN RISE TO SMALL CRAFT ADVISORY 

LEVELS AGAIN LATER THIS AFTERNOON AND EVENING. THERE IS A SMALL 

CHANCE IT COULD HIT GALE AGAIN IN THE STRAIT FOR A COUPLE HOURS THIS 

EVENING BUT THAT IS NOT THE CURRENT FORECAST. 



A FRONT WILL WILL REACH WESTERN WASHINGTON LATER SATURDAY. THIS 

SYSTEM IS NOT ESPECIALLY STRONG BUT IT WILL PROBABLY BRING SOME LOW 

END SOUTHERLY SMALL CRAFT ADVISORY WINDS TO MOST OF THE WATERS AS IT 

MOVES THROUGH.



A STRONGER FRONT WILL REACH THE AREA SUNDAY NIGHT. THIS SYSTEM WILL 

LIKELY BRING SOLID SMALL CRAFT ADVISORY WINDS TO ALL WATERS...BOTH 

AHEAD OF THE FRONT AROUND SUNDAY EVENING AND IN STRONG ONSHORE FLOW 

BEHIND THE FRONT LATER SUNDAY NIGHT AND MONDAY. SCHNEIDER



&&



.SEW WATCHES/WARNINGS/ADVISORIES...

WA...NONE.

PZ...SMALL CRAFT ADVISORY CENTRAL AND EAST STRAIT OF JUAN DE FUCA.



&&



$$



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FXUS66 KSEW 261624

AFDSEW



AREA FORECAST DISCUSSION

NATIONAL WEATHER SERVICE SEATTLE WA

924 AM PDT FRI APR 26 2013



.SYNOPSIS...LOW CLOUDS ACROSS THE INTERIOR LOWLANDS WILL CLEAR THIS 

AFTERNOON WHILE RESIDUAL HIGH PRESSURE OVER THE REGION WEAKENS. 

INCREASING WEST FLOW ALOFT WILL BRING HIGH CLOUDS OVER THE AREA THIS 

AFTERNOON. A WEAK COLD FRONT WILL BRING A LITTLE LIGHT RAIN TO THE 

AREA SATURDAY. A STRONGER WETTER COLD FRONT WILL BRING MORE RAIN AND 

MOUNTAIN SNOW LATE SUNDAY AFTERNOON AND SUNDAY NIGHT. AN UPPER LEVEL 

TROUGH WILL BRING SOME SHOWERS MONDAY AND TUESDAY. WARMER AND DRY 

WEATHER WILL RETURN WITH AN UPPER LEVEL RIDGE WEDNESDAY AND THURSDAY.



&&



.SHORT TERM...THE MARINE PUSH DEVELOPED PRETTY MUCH AS EXPECTED 

OVERNIGHT COVERING MOST OF THE INTERIOR LOWLANDS IN STRATUS THIS 

MORNING. ALTHOUGH THE STRATUS DID SPREAD A BIT FARTHER EASTWARD THAN 

EXPECTED OVER THE EAST PUGET SOUND LOWLANDS. EXPERIMENTAL GOES WEST 

CLOUD THICKNESS IMAGERY PUTS TOPS AROUND 1200 FEET THIS MORNING. 

UNFORTUNATELY THERE ARE NO PIREPS TO VALIDATE THAT. ONSHORE FLOW IS 

WEAK THIS MORNING AND THE STRATUS IS STILL SHALLOW ENOUGH TO EXPECT 

A BURN OFF AROUND MIDDAY. THIS IS SUPPORTED BY 12Z NAM TIME-HEIGHT 

SECTIONS. THE UPPER LEVEL RIDGE HAS FLATTENED OVERNIGHT WITH THE 

AXIS OVER E WA THIS MORNING AS IT DEPARTS...PUTTING W WA UNDER W 

FLOW ALOFT. HIGH CLOUDS JUST OFFSHORE WILL SPREAD OVER MAINLY THE 

COAST AND N PART THIS AFTERNOON. CURRENT FORECAST GOES WITH PARTLY 

SUNNY THIS AFTERNOON DUE TO THE HIGH CLOUDS...BUT IT COULD EASILY BE 

MOSTLY SUNNY. THE AIR MASS REMAINS WARM ALOFT BUT THE COOLING FROM 

THE MARINE AIR SHOULD STILL KNOCK OFF A FEW DEGREES FROM TODAYS MAX 

TEMPS.



ONSHORE FLOW WILL BE WEAKER TONIGHT SO THE COVERAGE OF STRATUS OVER 

THE INTERIOR SHOULD BE A LITTLE LESS SATURDAY MORNING...ALTHOUGH ALL 

AREAS WILL PROBABLY SEE SOME. 



MODELS REMAIN ON TRACK WITH THE WEAK COLD FRONT ARRIVING ON 

SATURDAY. THE 12Z GFS AND NAM ARE A LITTLE FASTER THAN PREVIOUS 

RUNS...BUT STILL BRING PRECIP OVER THE N PART OF W WA SATURDAY 

MORNING...THEN DOWN OVER PUGET SOUND AND THE CENTRAL COAST IN THE 

AFTERNOON. THE FRONT WEAKENS RAPIDLY OVER THE SW INTERIOR LATE 

SATURDAY. 



POST-FRONTAL ONSHORE FLOW AND WSW FLOW ALOFT SATURDAY NIGHT THROUGH 

SUNDAY MORNING WILL MAINTAIN A CHANCE OF SHOWERS OVER THE 

AREA...PARTICULARLY OVER THE MOUNTAINS. THE ONSHORE FLOW WILL 

PROBABLY ALLOW A CONVERGENCE ZONE TO SET UP OVER N PUGET SOUND.



THE GFS AND ECMWF REMAIN PRETTY CLOSE ON TIMING WITH THE NEXT 

STRONGER AND WETTER COLD FRONT LATE SUNDAY. PER THE GFS SOME LIGHT 

RAIN COULD SPREAD INLAND LATE SUNDAY AFTERNOON...BUT THE MAIN RAIN 

WILL BE SUNDAY NIGHT. THE MAIN ISSUE AT THIS POINT WILL BE SNOW 

AMOUNTS AND LEVELS OVER THE CASCADES. KAM



.LONG TERM...PREVIOUS DISCUSSION FROM THE 410 PM AFD...GOOD 

AGREEMENT IN THE EXTENDED MODEL SOLUTIONS EARLY ON WITH A POST FRONT 

TROUGH OVER THE AREA ON MONDAY KEEPING SHOWERS IN THE FORECAST. 

MODEL SOLUTION DIVERGE ON TUESDAY WITH THE ECMWF KEEPING SOME 

TROUGHINESS IN THE AREA WHILE THE GFS STARTS BUILDING A RIDGE. WITH 

THE UNCERTAINTY WILL KEEP CHANCE POPS IN THE FORECAST. GOOD 

AGREEMENT ON DAY 6 AND 7 WITH AN UPPER LEVEL RIDGE OVER THE AREA. 

GFS IS A LITTLE STRONGER WITH THE RIDGING WITH 500 MB HEIGHTS 

APPROACHING 580 DM. IF THIS VERIFIES NEXT WEDNESDAY AND THURSDAY 

COULD SURPASS THE LAST COUPLE OF DAYS FOR THE WARMEST DAYS OF THE 

YEAR SO FAR. FELTON 



&&



.HYDROLOGY...

FLOODING IS NOT EXPECTED THE NEXT 7 DAYS.



&&



.AVIATION...AN UPPER LEVEL RIDGE OVER THE AREA WILL WEAKEN AND 

FLATTEN THROUGH TONIGHT WITH WESTERLY FLOW ALOFT. LIGHT TO MODERATE 

ONSHORE FLOW WILL PREVAIL THROUGH TONIGHT. THE AIR MASS IS STABLE 

WITH WIDESPREAD LOW LEVEL MOISTURE. THE LOW LEVEL MOISTURE WILL MIX 

OUT MIDDAY. HIGH LEVEL MOISTURE WILL INCREASE LATE THIS AFTERNOON 

AND TONIGHT.  



STRATUS FILLS THE INTERIOR VALLEYS FROM KBLI SOUTHWARD AND THE 

COASTAL ZONES FROM KUIL SOUTHWARD. OBSERVATIONS SHOW CLOUD BASES 

003-008 AND GOES SATELLITE CLOUD THICKNESSES ARE 004-010. MOISTURE 

ADVECTION IS LIGHT...SO LOCAL TOOLS BASED ON INSOLATION THAT SHOW A 

BREAKOUT 17Z-18Z APPEAR ON TRACK FOR THE CENTRAL PUGET SOUND 

AREA...POSSIBLY A COUPLE HOURS LATER ON THE COAST. 



VFR CONDITIONS WILL DOMINATE THIS AFTERNOON THROUGH LATE TONIGHT AS 

HIGH LEVEL MOISTURE AHEAD OF AN INCOMING FRONTAL SYSTEM THAT EXTENDS 

SW FROM THE QUEEN CHARLOTTE SOUND MOVES SOUTHEAST TOWARD THE AREA. 

WITH THE INCREASE IN MID AND HIGH LEVEL MOISTURE LATE 

TONIGHT...EXPECT THE COVERAGE OF STRATUS TO BE ONLY PATCHY SATURDAY 

MORNING. ALBRECHT



KSEA...STRATUS WITH BASES 005 AND TOPS 009-012 WILL SCATTER OUT BY 

18Z. EXPECT ONLY MID AND HIGH LEVEL MOISTURE THROUGH TONIGHT. WINDS 

SOUTH 5 KT THIS MORNING WILL BECOME SOUTHWEST 6-10 KT IN THE 

AFTERNOON AND EVENING HOURS. ALBRECHT



&&



.MARINE...MODERATE ONSHORE FLOW WILL PREVAIL THROUGH TONIGHT. THE 

ONSHORE FLOW WILL EASE LATER TONIGHT AS A FRONTAL SYSTEM APPROACHES 

FROM THE WEST. THROUGH TONIGHT A SMALL CRAFT ADVISORY IS IN EFFECT 

FOR THE CENTRAL STRAIT OF JUAN DE FUCA AND THE EAST ENTRANCE.



A FRONTAL SYSTEM THAT EXTENDS SOUTHWESTWARD FROM THE QUEEN CHARLOTTE 

SOUND WILL MOVE ACROSS THE COASTAL WATERS SATURDAY AFTERNOON AND 

THROUGH THE INLAND WATERS SATURDAY EVENING. EXPECT SMALL CRAFT 

ADVISORY SOUTH TO SOUTHWEST WINDS ON SATURDAY OVER THE COASTAL 

WATERS. PUGET SOUND AND HOOD CANAL WILL ALSO LIKELY SEE SMALL CRAFT 

ADVISORY CONDITIONS ON SATURDAY AS SOUTHERLY GRADIENTS ARE ENHANCED 

BY WESTERLY FLOW ALOFT INTERACTING WITH THE OLYMPICS.



CONDITIONS ALONG THE COAST AND IN PUGET SOUND WILL RELAX BEHIND THE 

FRONT SATURDAY EVENING WHILE INFLOW THROUGH THE STRAIT OF JUAN DE 

FUCA INCREASES FOR SMALL CRAFT ADVISORY CONDITIONS THERE. SOUTH TO 

SOUTHWEST FLOW ALONG THE COAST AND IN THE PUGET SOUND AREA WILL 

INCREASE AGAIN SUNDAY EVENING AS A STRONGER FRONT MOVES THROUGH THE 

AREA FROM THE WEST. 



STRONG POST FRONTAL ONSHORE FLOW WILL DOMINATE MONDAY AND TUESDAY OF 

NEXT WEEK. ALBRECHT 



&&



.SEW WATCHES/WARNINGS/ADVISORIES...

WA...NONE.

PZ...SMALL CRAFT ADVISORY CENTRAL AND EAST STRAIT OF JUAN DE FUCA.



&&



$$



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FXUS66 KSEW 141622

AFDSEW



AREA FORECAST DISCUSSION

NATIONAL WEATHER SERVICE SEATTLE WA

922 AM PDT FRI JUN 14 2013



.SYNOPSIS...THE LINGERING EFFECTS OF ONSHORE FLOW WILL KEEP SKIES 

MOSTLY CLOUDY THROUGH MID THIS AFTERNOON. SKIES WILL CLEAR LATE THIS 

AFTERNOON AND TONIGHT AS A SMALL UPPER LEVEL RIDGE MOVES ACROSS THE 

AREA. A LARGE UPPER LEVEL LOW WELL OFFSHORE WILL BRING WARM 

SOUTHERLY FLOW ALOFT THIS WEEKEND LEADING TO MOSTLY SUNNY AND WARM 

CONDITIONS. MOSTLY CLOUDY SKIES WITH A CHANCE OF SHOWERS WILL RETURN 

NEXT WEEK AS THE UPPER LEVEL LOW GRADUALLY NEARS THE AREA THEN MOVES 

INLAND ON WEDNESDAY.



&&



.SHORT TERM...ONSHORE FLOW OVERNIGHT HAS BROUGHT A SUBSTANTIAL 

MARINE LAYER TO W WA THIS MORNING. VISIBLE SATELLITE 

IMAGERY...OBS...AND THE NEW EXPERIMENTAL LOW CLOUD THICKNESS DATA 

SHOW CLOUD BASES AROUND PUGET SOUND AROUND 3000 FEET WITH TOPS 

ANYWHERE FROM 4600 TO 5500 FEET. CLOUD BASES ARE LOWER OVER THE N 

INTERIOR IN SPOTS WITH MVFR CIGS. CLOUD THICKNESSES SEEM TO BE 

RUNNING 1000-1500 FEET IN AREAS WHERE THERE ARE NO BREAKS IN THE 

OVERCAST. WITH THE HIGH CLOUD BASES AND FAIRLY THICK CLOUD LAYERS IT 

WILL TAKE QUITE A WHILE FOR CLEARING TO DEVELOP. THERE WILL BE 

OCCASIONAL BREAKS IN THE OVERCAST TODAY...BUT CLEARING WILL HOLD OFF 

UNTIL LATE THIS AFTERNOON AND THIS EVENING. WITH 8 AM TEMPERATURES 

IN THE LOWER TO MID 50S...HIGHS TODAY IN THE 60S STILL LOOK GOOD.



A SMALL UPPER LEVEL RIDGE WILL MOVE OVER W WA THIS AFTERNOON AND 

TONIGHT...WHICH WILL ALTER THE SURFACE RIDGE ALONG THE COAST JUST 

ENOUGH FOR DRIER N LOW LEVEL FLOW TO DEVELOP LATE THIS AFTERNOON AND 

EVENING. COMBINED WITH THE NORMAL DIURNAL CLEARING...THIS WILL HELP 

SET UP A MOSTLY SUNNY WEEKEND. 



THE DOMINANT FEATURE THIS WEEKEND THROUGH NEXT WEEK WILL BE THE 

LARGE UPPER LEVEL LOW CURRENTLY OFFSHORE NEAR 49N/140W. MODELS AGREE 

THAT THE LOW WILL CONTINUE MOVING SLOWLY S THROUGH THIS 

WEEKEND...THEN HEAD SLOWLY E TOWARD THE COAST SUNDAY EVENING. THE 

POSITION OF THE LOW WILL ALLOW WARM S FLOW ALOFT TO DEVELOP OVER W 

WA SATURDAY...LEADING TO ABOUT 10 DEGREES OF WARMING AND HIGHS IN 

THE 70S. WITH CONTINUING WARM S FLOW ALOFT SUNDAY LOOKS LIKE A 

REPEAT OF SATURDAY. ONSHORE FLOW WILL BE WEAK THIS WEEKEND AND 

STRATUS WILL CONTINUE TO BLANKET THE COASTAL WATERS. STRATUS SHOULD 

COVER THE COAST EACH MORNING THIS WEEKEND AND THERE WILL PROBABLY BE 

SOME PATCHY STRATUS OVER THE INTERIOR...EXCEPT THAT THE 12Z NAM 

SHOWED A BIT MORE OVER THE SW INTERIOR SUNDAY MORNING. 



THE S FLOW ALOFT OVER THE AREA THIS WEEKEND MAY ALSO LEAD TO 

AFTERNOON CONVECTION ALONG THE CASCADE CREST. THIS LOOKS LIKE A 

COMBINATION OF DIURNAL INSTABILITY AIDED AT TIMES BY SMALL WEAK 

SHORTWAVE TROUGHS CROSSING THE AREA. THE CURRENT FORECAST FOR A 

CHANCE OF AFTERNOON AND EVENING THUNDERSTORMS OVER THE CASCADES 

LOOKS FINE. KAM



.LONG TERM...PREVIOUS DISCUSSION FROM THE 340 AM AFD...EXTENDED 

MODELS THROWING A BIT OF A WRINKLE INTO THE EXTENDED FORECAST THIS 

MORNING. FOR THE LAST FEW MODEL RUNS BEFORE THE 00Z RUN THE MODELS 

HAD BEEN REALLY CONSISTENT WITH THE TIMING OF THE EASTWARD MOVEMENT 

OF THE UPPER LEVEL LOW OFFSHORE MOVING THE LOW OVER WESTERN 

WASHINGTON ON TUESDAY. 00Z RUNS ARE SLOWER WITH THE EASTWARD 

PROGRESSION OF THE LOW BY ABOUT 12 HOURS WITH THE LOW STILL WEST OF 

130W ON MONDAY. WITH THE SLOWER TRACK OF THE LOW MODELS HAVE REDUCED 

THE CHANCES FOR SHOWERS OVER WESTERN WASHINGTON ON MONDAY AND BUMPED 

UP THE HIGH TEMPERATURES BY UP TO 5 DEGREES. SINCE THIS IS A NEW 

SOLUTION WILL STAY WITH THE CHANCE OF SHOWERS BEGINNING SUNDAY NIGHT 

BUT WILL UP THE MAX TEMPERATURES ON MONDAY CLOSER TO THE GUIDANCE. 

BOTH THE GFS AND ECMWF ARE VERY SIMILAR WITH THE UPPER LEVEL LOW 

MOVING INTO THE OFFSHORE WATERS ON TUESDAY...OVER WESTERN WASHINGTON 

ON WEDNESDAY...THEN MOVING OFF TO THE EAST ON THURSDAY. WILL STAY 

WITH THE BROADBRUSH CHANCE OF SHOWERS FORECAST THROUGH THURSDAY WITH 

HIGH TEMPERATURES A FEW DEGREES BELOW NORMAL. FELTON

 

&&



.AVIATION...ONSHORE FLOW WILL CONTINUE TODAY WITH ISOLATED SHOWERS 

OVER THE NORTH INTERIOR ENDING THIS MORNING. UPPER LEVEL RIDGING 

WILL MAINTAIN A STABLE AIR MASS. THE STRATUS LAYER OVER THE LOWLANDS 

IS AROUND 1000FT THICK WITH CIGS 2000-3000FT. EXPECT A SLOW BURN-OFF 

TODAY WITH CIGS BKN-OVC THROUGH 21-24Z. VFR CONDITIONS WILL PREVAIL 

TONIGHT WITH INCREASING CIRRUS CLOUDS ALOFT. 33



KSEA...EXPECT A SLOW BURN-OFF TODAY WITH CIGS HOVERING AROUND 3000 

FT. SURFACE WINDS WILL REMAIN S/SW AROUND 10KT. WINDS WILL TURN 

NORTHERLY TONIGHT BY 06Z. 33



&&



.MARINE...HIGH PRES OVER THE OFFSHORE WATERS AND LOWER PRES EAST OF 

THE CASCADES WILL PRODUCE LIGHT TO MODERATE ONSHORE FLOW ACROSS 

WESTERN WA THROUGH MON. THE CENTRAL/EAST STRAIT OF JUAN DE FUCA MAY 

SEE SMALL CRAFT ADVISORY WINDS SAT NIGHT AND SUN NIGHT. A BROAD 

SURFACE LOW /1012 MB/ WILL SPIN OVER THE OFFSHORE WATERS ON 

TUE...THEN WEAKEN AND SHIFT INLAND TUE NIGHT. 33



&&



.SEW WATCHES/WARNINGS/ADVISORIES...

WA...NONE.

PZ...NONE.



&&



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FXUS66 KSEW 181030

AFDSEW



AREA FORECAST DISCUSSION

NATIONAL WEATHER SERVICE SEATTLE WA

330 AM PDT THU JUL 18 2013



.SYNOPSIS...AN UPPER RIDGE WILL REMAIN OVER THE REGION INTO THE 

FIRST PART OF NEXT WEEK FOR DRY WEATHER. LOW LEVEL ONSHORE FLOW WILL 

PERSIST FOR AREAS OF LATE NIGHT AND MORNING CLOUDS. TEMPERATURES 

WILL REMAIN ABOVE NORMAL. 



&&



.SHORT TERM...SATELLITE IMAGERY SHOWS STRATUS FILLING BACK IN OVER 

THE INTERIOR IN THE LAST COUPLE OF HOURS WITH A CLEAR AREA DOWN THE 

I-5 CORRIDOR OVER THE SOUTHWEST INTERIOR. WHILE THE CROSS CASCADE 

GRADIENT REMAINS AROUND PLUS 6 MB THE REMAINDER OF THE INTERIOR 

GRADIENTS ARE PRETTY FLAT WITH KUIL-KBLI...KOLM-KBLI AND KHQM-KSEA 

ALL A MILLIBAR OR LESS. KOTH-KSEA GRADIENT IS ACTUALLY MINUS 1 MB. 

HAVE NOT GOTTEN ANY EXPERIMENTAL CLOUD DEPTH IMAGERY SINCE 07Z BUT 

AT THAT TIME MOST OF THE STRATUS DECK WAS A 1000 FEET OR LESS THICK. 

MODEL CROSS SECTIONS SHOW WINDS IN THE LOWER LEVELS LIGHT TO 

NORTHERLY TODAY. THE VAD WIND PROFILER ON THE KLGX RADAR ALREADY HAS 

NORTHWESTERLY WINDS UP TO 3000 FEET. WITH THE LIGHT GRADIENTS AND 

RELATIVELY THIN CLOUD DECK EXPECT THE STRATUS TO BURN BACK OFF THE 

COAST BY THIS AFTERNOON. HIGH TEMPERATURES WARMING UP VERSUS 

YESTERDAY WITH THE MODEL 850 MB TEMPERATURES IN THE PLUS 15 TO 17C 

RANGE BY 00Z FRI. THIS WILL RESULT IN HIGHS NEAR 80 FROM SEATTLE 

SOUTHWARD. TEMPERATURES TO THE NORTH WILL BE A LITTLE COOLER WITH 

THE WINDS OFF THE WATER. EVEN WITH SOME SUNSHINE THIS AFTERNOON THE 

COASTAL SECTIONS WILL STAY IN THE 60S. 



LITTLE CHANGE IN THE PATTERN TONIGHT INTO FRIDAY. IF ANYTHING THE 

ONSHORE GRADIENTS GET A LITTLE WEAKER. MODEL CROSS SECTIONS SHOW 

STRONGER NORTHERLY WINDS IN THE 850 MB TO SURFACE LAYER. WITH THE 

LIGHTER GRADIENTS AND STRONGER NORTHERLIES IN THE LOWER LEVELS WILL 

CUT BACK ON THE AMOUNT OF CLOUD COVER OVER THE INTERIOR FRIDAY 

MORNING. TEMPERATURES ALOFT CONTINUE TO WARM A TOUCH WITH 850 MB 

TEMPERATURES A COUPLE OF DEGREES C WARMER. THIS ALONG WITH THE ADDED 

SUNSHINE OVER THE INTERIOR WILL RESULT IN HIGHS ON FRIDAY ABOUT 5 

DEGREES WARMER THAN TODAY. 



VERY WEAK UPPER LEVEL TROUGH MOVING DOWN IN THE NORTHWESTERLY FLOW 

ALOFT OVER WESTERN WASHINGTON SATURDAY MORNING. THE MAIN EFFECT THIS 

FEATURE WILL HAVE WILL BE TO STRENGTHEN ON THE ONSHORE FLOW A LITTLE 

AND COOL DOWN THE TEMPERATURES ALOFT BY A COUPLE OF DEGREES C. WINDS 

IN THE LOWER LEVELS CONTINUE TO BE NORTHERLY SATURDAY MORNING WHICH 

DOES NOT BODE WELL FOR THE STRATUS GETTING EAST OF THE PUGET SOUND. 

WITH THE COOLER TEMPERATURES ALOFT WILL CUT THE MAX TEMPS A COUPLE 

OF DEGREES ON SATURDAY VERSUS FRIDAY BUT STILL KEEP TEMPS ABOVE 

NORMAL. 



.LONG TERM...EXTENDED MODELS CONTINUING WITH THE IDEA OF LITTLE 

CHANGE IN THE WEATHER PATTERN THROUGH THE FIRST PART OF NEXT WEEK. 

FLAT UPPER LEVEL RIDGE OVER THE AREA WITH 500 MB HEIGHTS IN THE 

UPPER 570 DM TO MID 580 DM INTO TUESDAY. LOW LEVEL FLOW NEVER TURNS 

OFFSHORE SO NO HEAT WAVE IN STORE BUT TEMPERATURES WILL REMAIN A FEW 

DEGREES ABOVE NORMAL WITH LATE NIGHT AND MORNING LOW CLOUDS MAINLY 

WEST OF THE PUGET SOUND. THE MODEL SOLUTIONS START TO DIFFER ON DAY 

7 WITH THE ECMWF A LITTLE FASTER WITH THE APPROACH OF AN UPPER LEVEL 

TROUGH FROM THE NORTHWEST RESULTING IN LOWER 500 MB HEIGHTS AND A 

BIT STRONGER ONSHORE FLOW. THE MODELS HAVE BEEN BACKING OFF ON THE 

TIMING OF THIS FEATURE FOR THE LAST FEW RUNS SO FOR NOW WILL STAY 

WITH THE CURRENT FORECAST OF JUST A LITTLE COOLER ON DAY 7. FELTON



&&



.AVIATION...LIGHT WESTERLY FLOW ALOFT OVER WESTERN WASHINGTON WILL 

PREVAIL THROUGH TONIGHT AS AN UPPER LEVEL RIDGE BUILDS OVER THE 

PACIFIC NORTHWEST. LOW LEVEL FLOW WILL REMAIN WEAKLY ONSHORE. THE 

AIR MASS WILL REMAIN FAIRLY MOIST BELOW 4000 FT THIS MORNING THEN 

DRY SOMEWHAT...ESPECIALLY OVER THE WESTERN WASHINGTON INTERIOR. THE 

AIR MASS WILL BE MAINLY DRY TONIGHT EXCEPT FOR MOISTURE IN A SHALLOW 

MARINE LAYER...MAINLY ALONG THE COAST.



AT 2 AM A THIN LAYER OF STRATOCUMULUS CLOUDS WAS OVER THE WESTERN 

WASHINGTON INTERIOR...FOR SCATTERED TO LOCALLY OVERCAST COVERAGE  

WITH BASES AROUND 3000 FT. CLOUD COVERAGE ALONG THE COAST WAS 

SOMEWHAT THICKER AND LOWER WITH BASES 2000-2500 FT. THE CLOUDS WILL 

PROBABLY FILL IN A BIT DURING THE NEXT FEW HOURS...AND MOST OF THE 

FORECAST AREA SHOULD HAVE A BKN-OVC CEILING OF 2500-3500 FT BY DAY 

BREAK. CLEARING IS EXPECTED OVER THE WESTERN WASHINGTON INTERIOR 

LATE MORNING TO MIDDAY AND ALONG MUCH OF THE COAST LATE IN THE 

AFTERNOON. STRATUS WILL BE MAINLY ALONG THE COAST TONIGHT.



KSEA....VARIABLE WIND 6 KT OR LESS...BECOMING NORTHWEST 5-10 KT 

MIDDAY...THEN NORTHEAST TONIGHT. THERE WILL LIKELY BE A BKN-OVC 

CEILING AROUND 3000 FT THROUGH AROUND 18Z.   MCDONNAL



&&



.MARINE...HIGH PRESSURE WELL OFFSHORE AND LOW PRESSURE EAST OF THE 

CASCADES WILL MAINTAIN ONSHORE FLOW TODAY THROUGH MONDAY. THIS IS A 

TYPICAL SUMMER PATTERN. SMALL CRAFT ADVISORY WEST WINDS ARE LIKELY 

EACH LATE AFTERNOON AND EVENING IN THE CENTRAL AND EASTERN STRAIT OF 

JUAN DE FUCA. ALSO SMALL CRAFT ADVISORY NORTHWEST SEA BREEZE WINDS 

WILL PROBABLY DEVELOP SOME DAYS DURING THE LATE AFTERNOON AND 

EVENING HOURS OVER THE COASTAL WATERS.   MCDONNAL



&&



.SEW WATCHES/WARNINGS/ADVISORIES...

WA...NONE.

PZ...SMALL CRAFT ADVISORY THIS EVENING THROUGH LATE TONIGHT COASTAL 

       WATERS.

     SMALL CRAFT ADVISORY THIS AFTERNOON THROUGH LATE TONIGHT 

       CENTRAL AND EASTERN STRAIT OF JUAN DE FUCA.



&&



$$


















FXUS66 KSEW 281102

AFDSEW



AREA FORECAST DISCUSSION

NATIONAL WEATHER SERVICE SEATTLE WA

400 AM PDT SUN JUL 27 2013



.SYNOPSIS...A WEAK UPPER LEVEL TROUGH WILL REMAIN OVER THE PACIFIC 

NORTHWEST WITH LOW LEVEL ONSHORE FLOW. A CHANCE OF SHOWERS OR 

THUNDERSTORMS WILL DEVELOP IN THE CASCADES MONDAY AND CONTINUE FOR 

MOST OF THE WEEK.



&&



.SHORT TERM...SATELLITE IMAGERY SHOWS STRATUS ALONG THE COAST...OVER 

THE SOUTHWEST INTERIOR AND JUST WEST OF THE PUGET SOUND NEAR 

BREMERTON AT 10Z. SURFACE GRADIENTS ARE LIGHT ONSHORE. TEMPERATURES 

ARE MOSTLY IN THE 50S.



WEAK UPPER LEVEL TROUGH REMAINING OVER WESTERN WASHINGTON TODAY. 

WITH THE LIGHT ONSHORE GRADIENTS STRATUS WILL MAKE A LITTLE MORE 

EASTWARD MOVEMENT THIS MORNING BUT WITH THE LIGHT FLOW IN THE LOWER 

LEVELS DO NOT EXPECT THE STRATUS TO GET ALL THE WAY TO THE CASCADE 

FOOTHILLS. CLOUD THICKNESS IMAGERY HAS THE STRATUS DECK BETWEEN 

900-1400 FEET THICK. WITH THIS THICKNESS OF THE STRATUS AND THE 

ONSHORE GRADIENTS REMAINING LIGHT EXPECT THE STRATUS TO BURN BACK TO 

THE COAST BY THIS AFTERNOON. TEMPERATURES ALOFT ARE FAIRLY SIMILAR 

TO YESTERDAY BUT WITH A LITTLE MORE CLOUD COVER WILL GO FOR SLIGHTLY 

COOLER HIGHS TODAY...MOSTLY IN THE 70S FOR THE INTERIOR. 



WEAK UPPER LEVEL TROUGH REMAINING OVER WESTERN WASHINGTON TONIGHT 

AND MONDAY. WEST NORTHWESTERLY FLOW ALOFT BECOMING MORE WESTERLY ON 

MONDAY. NEITHER DIRECTION IS VERY FAVORABLE FOR THE DEVELOPMENT OF 

CONVECTION OVER THE MOUNTAINS BUT MODELS DO SHOW LIFTED INDEXES  

NEAR 0 OVER THE NORTH CASCADES MONDAY AFTERNOON. LITTLE CHANGE IN 

THE LOW LEVEL PATTERN WITH WEAK ONSHORE FLOW CONTINUING. THIS WILL 

PULL THE STRATUS BACK IN OVER THE INTERIOR LATE TONIGHT INTO MONDAY 

MORNING. IF ANYTHING THE MARINE LAYER LOOKS A LITTLE SHALLOWER 

MONDAY MORNING. IN ADDITION WITH THE TROUGH DIGGING OFFSHORE A BIT 

TEMPERATURES OVER WESTERN WASHINGTON WARM UP WITH MODEL 850 MB 

TEMPERATURES INDICATING ABOUT A 3 DEGREE C INCREASE 00Z MON TO 00Z 

TUE. WITH THE SHALLOWER MARINE LAYER AND WARMER TEMPERATURES ALOFT 

WILL ADD A COUPLE OF DEGREES TO THE MAX TEMPERATURES ON MONDAY 

PUTTING THE WARMEST LOCATIONS IN THE LOWER 80S. 



UPPER LEVEL TROUGH CONTINUING TO DIG OFF THE COAST MONDAY NIGHT INTO 

TUESDAY. LOW LEVEL FLOW REMAINING WEAK ONSHORE WITH A SHALLOW MARINE 

LAYER BRINGING STRATUS BACK INTO THE INTERIOR TUESDAY MORNING. ONCE 

AGAIN WITH THE LAYER BEING SHALLOW THE STRATUS WILL BURN BACK TO THE 

COAST BY MIDDAY. WITH THE DIGGING TROUGH FLOW ALOFT BECOMING 

SOUTHWESTERLY. AIR MASS DESTABILIZING OVER WESTERN WASHINGTON 

TUESDAY AFTERNOON WITH MODEL LIFTED INDEXES OVER THE CASCADES DOWN 

TO MINUS 2 TO 3. NOT MUCH MOISTURE TO WORK WITH TUESDAY AFTERNOON 

BUT WITH THE LOW LI'S WILL STAY WITH THE CHANCE OF SHOWERS OR 

THUNDERSTORMS IN THE CASCADES TUESDAY AFTERNOON. WARMING TREND IN 

THE TEMPERATURES ALOFT CONTINUING WITH THE FLOW ALOFT BECOMING MORE 

SOUTHERLY. WITH THE SHALLOW MARINE LAYER AND WARMER TEMPERATURES 

ALOFT TUESDAY LOOKS TO BE THE WARMEST DAY IN THE SHORT TERM WITH 70S 

AND LOWER 80S COMMON OVER THE INTERIOR. 



.LONG TERM...EXTENDED MODELS ONCE AGAIN IN GOOD AGREEMENT WITH A 

WEAK UPPER LEVEL LOW OFF THE COAST TUESDAY NIGHT GRADUALLY DRIFTING 

INTO WESTERN WASHINGTON THURSDAY. EVEN WITH THE LOW MOVING INTO THE 

AREA THE LOW IS FAIRLY WEAK. WILL KEEP THE SHOWER ACTIVITY CONFINED 

TO THE MOUNTAINS WEDNESDAY AND THURSDAY. SOME DIFFERENCES IN THE 

MODELS FRIDAY WITH THE ECMWF KICKING THE LOW OUT FASTER THAN THE 

GFS. BOTH MODELS HAVE SOME WEAK TROUGHINESS STILL IN THE AREA ON 

SATURDAY. WILL KEEP THE CHANCE OF SHOWERS IN THE FORECAST FOR 

CASCADES INTO SATURDAY. LOW LEVEL ONSHORE FLOW CONTINUING THROUGH 

THE EXTENDED PERIOD KEEPING THE MORNING CLOUDS AFTERNOON SUNSHINE 

FOR THE INTERIOR SCENARIO INTACT. TEMPERATURES WILL REMAIN NEAR 

NORMAL WITH HIGHS IN THE 70S COMMON FOR THE INTERIOR. FELTON



&&



.AVIATION...A BROAD UPPER TROUGH WILL REMAIN OVER THE AREA TODAY 

WITH CONTINUED LOW LEVEL ONSHORE FLOW. AIR MASS STABLE. STRATUS 

ALONG THE COAST AND PARTIALLY INLAND DOWN THE STRAIT OF JUAN DE FUCA 

AND THROUGH THE CHEHALIS GAP WILL BURN BACK TO THE COAST TODAY.



KSEA...SOUTH WIND WIND 3-6 KNOTS WILL BECOME WESTERLY THIS 

AFTERNOON. STRATUS PUSHING INTO THE SOUTH SOUND EARLY THIS MORNING 

IS EXPECTED TO REACH THE TERMINAL AROUND DAYBREAK. IT SHOULD LAST A 

FEW HOURS AND BURN OFF AROUND NOON. SCHNEIDER



&&



.MARINE...HIGH PRESSURE WILL REMAIN WELL OFFSHORE WITH LOWER 

PRESSURE EAST OF THE CASCADES. SMALL CRAFT ADVISORY NORTHWEST WINDS 

OVER THE OUTER COASTAL WATERS WILL EASE TODAY AS OFFSHORE HIGH 

PRESSURE WEAKENS. THERE COULD ALSO BE MARGINAL SMALL CRAFT ADVISORY 

WEST WINDS IN THE CENTRAL AND EASTERN STRAIT DURING THE EVENING 

HOURS IN THIS PATTERN. SCHNEIDER 

 

&&



.SEW WATCHES/WARNINGS/ADVISORIES...

WA...NONE.

PZ...SMALL CRAFT ADVISORY OUTER COASTAL WATERS.



&&



$$



YOU CAN SEE AN ILLUSTRATED VERSION OF THE FORECAST DISCUSSION AT 

WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML
















FXUS66 KSEW 291052

AFDSEW



AREA FORECAST DISCUSSION

NATIONAL WEATHER SERVICE SEATTLE WA

350 AM PDT MON JUL 29 2013



.SYNOPSIS...A WEAK UPPER LEVEL TROUGH WILL REMAIN OVER THE AREA 

TODAY. A WEAK UPPER LEVEL LOW WILL DEVELOP OFF THE COAST ON TUESDAY 

THEN SLOWLY DRIFT EAST MOVING INTO THE PACIFIC NORTHWEST LATER 

THURSDAY. AS THE LOW APPROACHES AND MOVES INLAND THE AIR MASS WILL 

BECOME MORE UNSTABLE INCREASING THE CHANCES FOR THUNDERSTORMS OVER 

THE CASCADES. THE LOW WILL MOVE EAST OF THE AREA ON FRIDAY WITH A 

RETURN TO TYPICAL SUMMER WEATHER FOR THE WEEKEND. 



&&



.SHORT TERM...SATELLITE IMAGERY SHOWS CLOUDS COVERING THE AREA ALONG 

THE COAST AND FROM ABOUT WHIDBEY ISLAND SOUTHWARD OVER THE INTERIOR. 

TEMPERATURES WERE IN THE 50S AT 10Z. 



SOMEWHAT SIMILAR DAY TO SUNDAY SHAPING UP WITH THE WEAK UPPER LEVEL 

TROUGH REMAINING OVER WESTERN WASHINGTON. ONSHORE GRADIENTS A LITTLE 

WEAKER THIS MORNING VERSUS YESTERDAY MORNING BUT CLOUD THICKNESS 

IMAGERY STILL SHOWS THE STRATUS LAYER 1000-1400 FEET THICK LIKE 

YESTERDAY MORNING EVEN WITH THE BASES ABOUT 1000 FEET HIGHER. LIGHT 

LOW LEVEL WINDS THIS MORNING BECOMING NORTHERLY THIS AFTERNOON. THIS 

COMBINED WITH THE UPPER LEVEL TROUGH WEAKENING SHOULD MAKE FOR A 

SLIGHTLY EARLIER BREAKOUT THIS AFTERNOON FOR MOST OF THE INTERIOR. 



500 MB HEIGHTS CONTINUE TO RISE TONIGHT INTO TUESDAY AS A WEAK UPPER 

LEVEL LOW FORMS OFF THE COAST PUSHING A TEMPORARY WEAK UPPER LEVEL 

RIDGE INTO WESTERN WASHINGTON. LOW LEVEL FLOW STILL LIGHT ONSHORE 

FOR ANOTHER ROUND OF MORNING CLOUDS BUT WITH NORTHERLY WINDS FROM 

THE SURFACE THROUGH 850 MB TONIGHT INTO TUESDAY MORNING THE MARINE 

LAYER WILL BE SHALLOWER LEADING TO AN EARLIER BREAKOUT AND WARMER 

HIGH TEMPERATURES...AT LEAST FOR THE INTERIOR. FLOW ALOFT BECOMING 

SOUTHERLY WITH THE DEVELOPMENT OF THE LOW OFFSHORE WITH THE AIR MASS 

BECOMING SOMEWHAT UNSTABLE TUESDAY AFTERNOON. NOT MUCH MOISTURE TO 

WORK WITH BUT LIFTED INDEXES ARE BELOW 0 OVER THE CASCADES TUESDAY 

AFTERNOON. WILL KEEP THE CHANCE OF SHOWERS OR THUNDERSTORMS IN THE 

FORECAST. 



UPPER LEVEL LOW DRIFTING TOWARDS THE OREGON COAST TUESDAY NIGHT INTO 

WEDNESDAY WITH SOUTHERLY FLOW ALOFT CONTINUING OVER WESTERN 

WASHINGTON. AIR MASS REMAINING SOMEWHAT UNSTABLE WHICH WILL HELP 

REDUCE THE MARINE LAYER ESPECIALLY OVER THE INTERIOR. AS THE LOW 

APPROACHES MID AND HIGH LEVEL CLOUDS WILL INCREASE MAKING WEDNESDAY 

A FILTERED SUNSHINE DAY. THERE THE POTENTIAL FOR A COLORFUL SUNRISE 

WEDNESDAY MORNING. WITH THE SOMEWHAT UNSTABLE AIR MASS THE CHANCE 

FOR CONVECTION OVER THE CASCADES WILL REMAIN IN THE FORECAST. 



.LONG TERM...EXTENDED MODELS IN GOOD AGREEMENT THIS MORNING WITH THE 

UPPER LEVEL LOW MOVING INTO OREGON ON THURSDAY. IF THE MODELS 

CONTINUE TO SHOW RUN TO RUN CONSISTENCY A CHANCE OF SHOWERS WILL 

HAVE TO BE ADDED TO THE LOWLAND FORECAST FOR AT LEAST THURSDAY AND 

MAYBE FRIDAY AS WELL DEPENDING ON HOW FAST THE LOW KICKS OUT OF THE 

AREA. BOTH THE ECMWF AND GFS HAVE THE LOW FAR ENOUGH TO THE EAST BY 

SATURDAY TO RETURN WESTERN WASHINGTON TO A MORE NORMAL SUMMERTIME 

PATTERN. FOR NOW...NO CHANGE TO THE EXTENDED FORECAST. FELTON



&&



.CLIMATE...FOUR YEARS AGO TODAY WAS POSSIBLY THE HOTTEST DAY ON 

RECORD IN WESTERN WASHINGTON. SEATTLE SET ITS ALL TIME RECORD HIGH 

TEMPERATURE OF 103 DEGREES. OLYMPIA TIED ITS ALL TIME HIGH WITH 104 

DEGREES. 



&&



.AVIATION...A BROAD UPPER LEVEL TROUGH WILL REMAIN OVER THE AREA 

TODAY WITH LOW LEVEL ONSHORE FLOW. THE AIR MASS IS STABLE EXCEPT 

SLIGHTLY UNSTABLE NEAR THE CASCADE CREST. THE AIR MASS IS DRY EXCEPT 

MOIST IN THE LOWER LEVELS.



STRATUS WILL COVER MUCH OF THE LOWLANDS THIS MORNING. IT WILL LIFT 

AND BURN BACK TO THE COAST IN THE AFTERNOON WITH DAYTIME HEATING. 

THERE WILL ALSO BE SOME MID CLOUDS FLOATING AROUND TODAY...MOSTLY 

EAST OF PUGET SOUND. 



KSEA...STRATUS AT THE TERMINAL SHOULD LIFT LATER THIS MORNING AND 

BURN OFF EARLY IN THE AFTERNOON. SOUTHERLY WIND 4-8 KNOTS BECOMING 

WEST/NORTHWEST LATE IN THE AFTERNOON OR EARLY IN THE EVENING.  

SCHNEIDER 



&&



.MARINE...HIGH PRESSURE WILL REMAIN WELL OFFSHORE WITH LOWER 

PRESSURE EAST OF THE CASCADES THROUGH THE END OF THE WEEK. A WEAK 

SURFACE LOW WILL FORM OVER VANCOUVER ISLAND TODAY AND PERSIST INTO 

THE MIDDLE OF THE WEEK. SCHNEIDER



&&



.SEW WATCHES/WARNINGS/ADVISORIES...

WA...NONE.

PZ...NONE.



&&



$$



WWW.WEATHER.GOV/SEATTLE



YOU CAN SEE AN ILLUSTRATED VERSION OF THE FORECAST DISCUSSION AT 

WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML








FXUS66 KSEW 030409

AFDSEW



AREA FORECAST DISCUSSION

NATIONAL WEATHER SERVICE SEATTLE WA

910 PM PDT FRI AUG 2 2013



.SYNOPSIS...AN UPPER LEVEL TROUGH OVER THE PACIFIC NORTHWEST WILL BE 

REPLACED BY A WEAK UPPER RIDGE BY EARLY NEXT WEEK. THE COOL SHOWERY 

WEATHER OF TODAY WILL GIVE WAY TO INCREASING SUNSHINE WITH WARMING 

TEMPERATURES OVER THE WEEKEND AND INTO EARLY NEXT WEEK.



&&



.SHORT TERM...CLOUDS CONTINUE TO WRAP WESTWARD AND SOUTHWESTWARD 

INTO THE AREA AROUND AN UPPER LEVEL LOW CENTERED OVER THE NORTHERN 

IDAHO PANHANDLE. THE AREA OF SHOWERS THAT ENDED THE REGIONS DRY 

SPELL TODAY CONTINUES TO DIMINISH AS IT DRIFTS SOUTHWARD INTO 

EXTREME SOUTHWEST WASHINGTON. SHOWERS OVER THE COASTAL RANGES OF 

SOUTHWESTERN BRITISH COLUMBIA AND OVER NORTH CENTRAL WASHINGTON ARE 

DIMINISHING AS THE MOVE WEST AND SOUTHWEST AWAY FROM THE UPPER LOW 

AND TOWARD OUR AREA. THE DRYING TREND ON RADAR CONFIRMS WHAT SHORT 

RANGE MODELS SHOW...ADDITIONAL SHOWER ACTIVITY APPEARS UNLIKELY TO 

MAKE IT INTO THE AREA WITH THE POSSIBLE EXCEPTION OF THE NORTH 

CASCADES THIS EVENING. WILL REDUCE POPS TO 20 MOST AREAS TONIGHT AND 

REMOVE THEM FOR SATURDAY...EXCEPT IN THE CASCADES WHERE THE REMNANT 

TROUGH INSOLATION MAY ALLOW ISOLATED SHOWERS TO DEVELOP.



CONDITIONS WILL GRADUALLY DRY OUT ACROSS THE AREA ON SATURDAY. THE 

QUESTION IS...HOW LONG WILL IT TAKE FOR THE CLOUDS TO THIN/SCATTER 

OUT SUFFICIENTLY TO ALLOW THE EARLY AUGUST SUN TO START A GOOD 

WARMING TREND. THE INCOMING 00Z NAM12 SHOWS BROKEN CLOUDS PERSISTING 

OVER THE AREA THROUGH MUCH OF SATURDAY AFTERNOON...WHICH WILL HOLD 

MAXIMUM TEMPERATURES OVER THE AREA IN THE UPPER 60S TO MID 70S MOST 

AREAS. THE 18Z GFS APPEARS A BIT AGGRESSIVE WITH THE CLEARING AND 

WARMING. CURRENT FORECAST TEMPERATURES FOR SATURDAY LOOK GOOD. 



MORNING CLOUDS WILL GIVE WAY TO AFTERNOON SUNSHINE ON SUNDAY...AND 

CLEARING IS EXPECTED TO OCCUR EARLY ENOUGH TO ALLOW TEMPERATURES TO 

RISE INTO THE MID 70S TO LOWER 80S MOST PLACES. THE NAM12 MOS 

TEMPERATURES APPEAR MORE REASONABLE THAN THE WARMER GFS. CURRENT 

FORECASTS FOLLOW THE SLIGHTLY COOLER NAM12 SOLUTION AND WILL BE 

MAINTAINED. ALBRECHT  



.LONG TERM...FROM THE PREVIOUS LONG TERM DISCUSSION...500MB HEIGHTS 

RECOVER TO AROUND 580DM NEXT WEEK. THE UPPER TROUGH OVER THE PACNW 

WILL BE REPLACED BY A WEAK UPPER RIDGE...BUT A WEAK UPPER LOW WILL 

REMAIN JUST OFF CALIF NEXT WEEK. THAT LOW IS NOT TOO LIKELY TO 

AFFECT WESTERN WA ALTHOUGH A LITTLE MOISTURE MAY EVENTUALLY BRING A 

CHANCE OF SHOWERS OR A FEW THUNDERSTORMS TO THE CASCADES...MAINLY 

NEAR THE CREST. MOST OF WESTERN WA WILL HAVE A STABLE AIR MASS WITH 

A FAIR BIT OF MARINE INFLUENCE...AT LEAST IN THE NIGHT AND MORNING 

HOURS. SURFACE LOW PRESSURE WILL BE INLAND WITH HIGHER PRESSURE JUST 

OFFSHORE...AND THE WEATHER WILL LIKELY RETURN TO A TYPICAL REGINE OF 

AREAS OF NIGHT AND MORNING LOW CLOUDS WITH AFTERNOON SUN. HIGHS NEXT 

WEEK WILL PROBABLY BE IN THE 60S TO LOWER 70S ON THE COAST WITH 70S 

TO LOWER 80S IN THE INTERIOR.



&&



.AVIATION...WEAK CYCLONIC FLOW ALOFT WILL CONTINUE OVER THE REGION 

THROUGH SATURDAY. LIGHT NORTHERLY FLOW ALOFT AND LOW LEVEL ONSHORE 

FLOW WILL PREVAIL. THE AIR MASS HAS STABILIZED OVER THE AREA. THE 

TSTMS OVER BRITISH COLUMBIA ARE NOT EXPECTED TO MOVE INTO THE AREA. 



CIGS ARE EXPECTED TO BE MAINLY IN THE 1-3K FT RANGE OVERNIGHT... 

ALTHOUGH THERE WILL BE AREAS OF CIGS IN THE 500 TO 1K FT RANGE. THE 

SHORT RANGE ENSEMBLE FORECAST /SREF/ INDICATED THE POSSIBILITY OF 

FOG /VSBYS AOB 3SM/ LATER TONIGHT THRU SATURDAY MORNING ON THE COAST 

AND SW PART OF THE FORECAST AREA. CONFIDENCE OF THIS OCCURRING WAS 

NOT HIGH ENOUGH TO MENTION IN THE KHQM AND KOLM TAFS.



KSEA...CIGS ARE EXPECTED TO GENERALLY BE IN THE 1-2K FT RANGE 

OVERNIGHT. THERE IS A POSSIBILITY THAT THEY MAY BRIEFLY POP UP ABOVE 

3K FT OR BELOW 1K FT. 



&&



.MARINE...

THERE WERE TWO SWELLS PRESENT. THE PRIMARY /FRESH/ SWELL WAS RUNNING 

2-3 FT FROM THE NW AT 6-7 SECONDS. THERE WAS A SECONDARY SWELL OF

A HALF FOOT AT 15 OR 16 SECONDS FROM THE SOUTH-SOUTHWEST. THE 

FORECAST WAS UPDATED TO REFLECT THE PRIMARY SWELL.



THE SHORT RANGE ENSEMBLE FORECAST /SREF/ INDICATED THE POTENTIAL FOR 

FOG DEVELOPMENT OVER THE COASTAL WATERS AND WEST ENTRANCE TO THE 

STRAIT OF JUAN DE FUCA LATER TONIGHT. AT THIS TIME...CONFIDENCE WAS 

NOT HIGH ENOUGH TO INCLUDE A MENTION OF FOG IN THE FORECAST. WILL 

MONITOR TRENDS OF THE EXPERIMENTAL GEOCAT PRODUCT...IN PARTICULAR

THE SATELLITE-DERIVED PROBABILITY OF VISIBILITY OF LESS THAN 1 NM 

AND CLOUD BASES AT OR BELOW 500 FEET. FOG WILL PROBABLY BE MORE 

LIKELY SATURDAY NIGHT THROUGH SUN MORNING.



MEANWHILE...ONSHORE FLOW WILL PERSIST THROUGH THE MIDDLE OF NEXT 

WEEK. WINDS WILL HAVE A BETTER POTENTIAL OF REACHING SMALL CRAFT 

ADVISORY SPEEDS ACROSS THE CENTRAL AND EASTERN STRAIT OF JUAN DE 

FUCA DURING THE AFTERNOONS AND EVENINGS BEGINNING SATURDAY. 



&&



.SEW WATCHES/WARNINGS/ADVISORIES...

WA...NONE.

PZ...NONE.



&&



$$



YOU CAN SEE AN ILLUSTRATED VERSION OF THE FORECAST DISCUSSION AT 

WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML




























FXUS66 KSEW 041029

AFDSEW



AREA FORECAST DISCUSSION

NATIONAL WEATHER SERVICE SEATTLE WA

330 AM PDT SUN AUG 4 2013



.SYNOPSIS...A WEAK UPPER TROUGH OVER THE AREA TODAY WILL SHIFT EAST 

WITH AN UPPER RIDGE BUILDING IN FROM THE WEST MONDAY. THE RIDGE 

WILL REMAIN OVER THE AREA FOR MOST OF THE WEEK.



&&



.SHORT TERM...A WEAK UPPER TROUGH WILL LINGER OVER THE AREA TODAY. 

THERE WILL BE ENOUGH MOISTURE AND INSTABILITY FOR A CHANCE OF 

THUNDERSTORMS OVER THE CASCADES IN THE AFTERNOON AND EVENING. LOW 

LEVEL FLOW IS CURRENTLY PRETTY WEAK. SATELLITE SHOWS AREAS OF 

LINGERING LOW CLOUDS NEAR THE COAST...EAST OF PUGET SOUND...AND 

PUSHING DOWN THE STRAIT. THE REMAINDER OF THE AREA SHOULD AT LEAST 

PARTIALLY FILL IN WITH LOW CLOUDS IN THE NEXT FEW HOURS...THEN THE 

CLOUDS WILL BURN OFF LATER TODAY FOR A SUNNY DAY. HIGHS TODAY WILL 

WARM A FEW DEGREES COMPARED TO YESTERDAY. THERE SHOULD BE LESS LOW 

CLOUDS MONDAY AND TUESDAY MORNINGS AS THE UPPER RIDGE BUILDS OVER 

THE AREA AND THE LOW LEVELS DRY. THERE WILL ALSO BE A FEW MORE 

DEGREES OF WARMING. SCHNEIDER 



.LONG TERM...AN UPPER RIDGE WILL BE IN CONTROL FOR MOST OF THE WEEK. 

THIS WILL KEEP THE WEATHER DRY WITH HIGHS A LITTLE ABOVE NORMAL AND 

CLOUDS LIMITED TO NIGHT AND MORNING HOURS...MAINLY NEAR THE COAST. 

AN UPPER LOW OVER CALIFORNIA WILL BEGIN LIFTING NORTH FRIDAY OR 

SATURDAY. THIS WILL BRING SOME ADDED MOISTURE AND INSTABILITY AND A 

CHANCE OF THUNDER TO THE CASCADES. SCHNEIDER 



&&



.AVIATION...A WEAK UPPER TROF WILL REMAIN OVER THE AREA TODAY FOR 

LIGHT NW FLOW ALOFT. CONTINUED LOW LEVEL ONSHORE FLOW. THE AIR MASS 

WILL DESTABILIZE THIS AFTERNOON. THE SHORT RANGE ENSEMBLE FORECAST 

/SREF/ WAS INDICATING A POSSIBILITY OF TSTMS OVER THE MTNS BETWEEN 

2100 UTC TODAY AND 0600 UTC MON.



MEANWHILE...THERE WERE AREAS OF VSBYS AOB 1SM AND CIGS AOB 500 FT 

THIS MORNING. OVERALL...THERE WAS LESS STRATUS OVER THE AREA THAN AT 

THE SAME TIME YESTERDAY. TOPS WERE RUNNING BETWEEN 1K AND 1500 FT 

PER THE EXPERIMENTAL SATELLITE-DERIVED CLOUD THICKNESS PRODUCT. 

EXPECT THE CLOUDS/FOG TO BURN OFF OVER THE INTERIOR BY 1900 UTC... 

AND BY 2100 UTC OVER THE COAST. ALTHOUGH...AREAS OF LOW CLOUDS MIGHT 

LINGER OVER THE COAST.     



KSEA...CONFIDENCE IN THE FORECAST WAS LOW. THERE IS A DISTINCT 

POSSIBILITY THAT VFR CONDITIONS WILL PREVAIL ACROSS THE TERMINAL ALL 

DAY TODAY. THERE IS ALSO A POSSIBILITY THAT THERE WILL BE A LOW CIG 

/NEAR 500 FT/ AND FOG /VSBY AOB 3SM/ THIS MORNING. THE UPCOMING TAF 

PACKAGE WILL SHOW A COMPROMISE BETWEEN THE TWO EXTREMES. IF ANY LOW 

CLOUDS AND FOG DO MATERIALIZE...VFR CONDITIONS SHOULD RETURN BY 1900 

UTC. 



&&



.MARINE...THERE WAS SOME PATCHY FOG OVER THE WATERS EARLY THIS 

MORNING. THE VISIBILITY MIGHT BE BELOW 1 NM IN SPOTS. FOG WILL 

PROBABLY BE MORE WIDESPREAD AND DENSER MON MORNING. MEANWHILE...HIGH 

PRES OFFSHORE AND LOWER PRES E OF THE CASCADES WILL RESULT IN LIGHT 

TO MODERATE ONSHORE FLOW THROUGH THU. 



&&



.SEW WATCHES/WARNINGS/ADVISORIES...

WA...NONE.

PZ...SMALL CRAFT ADVISORIES ARE IN EFFECT FOR THE CENTRAL AND 

     EASTERN STRAIT OF JUAN DE FUCA.



&&



$$



WWW.WEATHER.GOV/SEATTLE



YOU CAN SEE AN ILLUSTRATED VERSION OF THE FORECAST DISCUSSION AT 

WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML










FXUS66 KSEW 061020 CCA

AFDSEW



AREA FORECAST DISCUSSION...CORRECTED 

NATIONAL WEATHER SERVICE SEATTLE WA

320 AM PDT TUE AUG 6 2013



CORRECTED TO ADD CLOUD TOP INFO TO THE AVIATION SEGMENT.



.SYNOPSIS...HIGH PRESSURE ALOFT WILL CONTINUE OVER THE PACIFIC 

NORTHWEST THROUGH THE WEEK...WITH WEAK ONSHORE FLOW AT LOW LEVELS. 

TEMPERATURES WILL MODERATE SLIGHTLY BY MIDWEEK BUT REMAIN NEAR OR A 

LITTLE ABOVE NORMAL. AN UPPER LEVEL LOW MAY TRIGGER SOME SHOWERS AND 

THUNDERSTORMS OVER THE CASCADES FRIDAY THROUGH EARLY NEXT WEEK. 



&&



.SHORT TERM...WEAK WESTERLY FLOW ALOFT CONTINUES OVER WESTERN 

WASHINGTON WITH A FLAT UPPER RIDGE OVER THE REGION. THE AIR MASS IS 

FAIRLY WARM WITH 500 MB HEIGHTS AROUND 5820 METERS...AND THE 

FREEZING LEVEL AROUND 13000 FT. LOW LEVEL ONSHORE FLOW REMAINS 

WEAKLY ONSHORE. MARINE STRATUS HAS BEEN MOVING INLAND FROM THE COAST 

OVERNIGHT...THROUGH THE STRAIT OF JUAN DE FUCA AND THE LOWER 

CHEHALIS VALLEY. 



MARINE STRATUS WILL CONTINUE TO INCREASE OVER THE WESTERN WASHINGTON 

LOWLANDS DURING THE NEXT FEW HOURS. IT WILL LIKELY COVER MUCH OF THE 

AREA TO THE NORTH AND SOUTH OF SEATTLE...BUT SEATTLE ITSELF WILL 

PROBABLY REMAIN MOSTLY CLEAR. THE STRATUS WILL BURN OFF TO THE 

IMMEDIATE COAST DURING THE LATE MORNING AND EARLY AFTERNOON...FOR 

MOSTLY SUNNY SKIES. TEMPERATURES WILL BE SIMILAR OR MAYBE A DEGREE 

OR TWO HIGHER THAN MONDAY.



UPPER HEIGHTS WILL FALL A BIT TONIGHT AND WEDNESDAY...AS THE WEAK 

UPPER LOW CURRENTLY WELL OFF THE CALIFORNIA COAST MOVES INTO ITS 

OFFSHORE WATERS. ONSHORE FLOW WILL STRENGTHEN SLIGHTLY BUT STILL 

REMAIN RATHER WEAK. SO THE MARINE STRATUS WILL PUSH INLAND AGAIN 

TONIGHT AND EARLY WEDNESDAY MORNING...PERHAPS A BIT DEEPER THAN THIS 

MORNING. IT WILL AGAIN BE A SUNNY AFTERNOON...EXCEPT ALONG THE 

IMMEDIATE COAST. HIGH TEMPERATURES WEDNESDAY SHOULD BE A FEW DEGREES 

COOLER THAN TODAY BUT STILL SEVERAL DEGREES ABOVE NORMAL.



UPPER HEIGHTS WILL FALL A BIT MORE WEDNESDAY NIGHT AND THURSDAY AS 

THE UPPER LOW MOVES ONTO THE NORTHERN CALIFORNIA COAST. LOW LEVEL 

ONSHORE FLOW WILL INCREASE MORE...ESPECIALLY THE SOUTHERLY COMPONENT 

OF THE PRESSURE GRADIENT...AND MARINE STRATUS WILL PROBABLY COVER 

MUCH OF THE WESTERN WASHINGTON INTERIOR LOWLANDS BY THURSDAY 

MORNING. IT SHOULD AGAIN GIVE WAY TO MOSTLY SUNNY SKIES...AND HIGH 

TEMPERATURES WILL BE NEAR TO A LITTLE ABOVE NORMAL.   MCDONNAL



.LONG TERM...THE WEAK UPPER LOW WILL PROBABLY BE OVER NORTHERN 

CALIFORNIA ON FRIDAY. IT SHOULD DRIFT SLOWLY NORTH-NORTHWEST... 

MOVING INTO THE WASHINGTON OFFSHORE WATERS ON SUNDAY OR MONDAY. ITS 

PROXIMITY TO THE FORECAST WILL RESULT IN A WEAKLY UNSTABLE AIR MASS 

OVER THE MOUNTAINS...SO ISOLATED SHOWERS AND THUNDERSTORMS COULD 

DEVELOP OVER THE CASCADES EACH DAY MAINLY IN THE AFTERNOONS AND 

EVENINGS. 



IT WILL NOT HAVE MUCH IMPACT ON THE REST OF WESTERN WASHINGTON 

THOUGH. THE AIR MASS WILL REMAIN RELATIVELY WARM WITH ONLY WEAK 

ONSHORE LOW LEVEL FLOW. SO THE PATTERN THAT HAS BEEN SO COMMON THIS 

SUMMER WILL CONTINUE...WITH COASTAL STRATUS MOVING INLAND DURING THE 

NIGHT AND EARLY MORNING HOURS AND THEN GIVING WAY TO MAINLY SUNNY 

AFTERNOONS. DAYTIME TEMPERATURES WILL STILL BE NEAR TO SLIGHTLY 

ABOVE NORMAL.   MCDONNAL



&&



.AVIATION...AN UPPER RIDGE WILL PREVAIL OVER THE REGION TODAY FOR 

WLY FLOW ALOFT. CONTINUED LOW LEVEL ONSHORE FLOW. THE AIR MASS WILL 

BECOME WEAKLY UNSTABLE OVER THE MTNS THIS AFTERNOON FOR A FEW 

CUMULUS CLOUDS.



MEANWHILE...LIFR CIGS AND/OR VSBYS PREVAILED OVER THE COAST...PARTS 

OF THE SW INTERIOR...AND THE LAND AREAS ADJACENT TO THE STRAIT OF 

JUAN DE FUCA...ADMIRALTY INLET...AND NORTHERN INLAND WATERS EARLY 

THIS MORNING. PER THE SATELLITE DERIVED FOG PRODUCT...IT APPEARED 

THAT THERE MIGHT BE LOCALIZED LIFR CIGS AND/OR VSBYS OVER THE FAR S 

PUGET SOUND AT THIS TIME. TOPS WERE RUNNING BETWEEN 800 AND 1100 FT 

PER THE SATELLITE DERIVED CLOUD THICKNESS PRODUCT. THE LOW STRATUS/ 

FOG WILL PROBABLY BECOME SLIGHTLY MORE WIDESPREAD OVER THE INTERIOR 

THIS MORNING BEFORE DISSIPATING BY 1900 UTC. ANTICIPATE VFR 

CONDITIONS OVER THE ENTIRE AREA BY 2100 UTC.     



KSEA...VFR CONDITIONS WILL PERSIST OVER THE TERMINAL. ANTICIPATE LOW 

STRATUS AND/OR FOG W OF THE TERMINAL OR OVER THE WATER BETWEEN 1200 

AND 1700 UTC.



&&



.MARINE...

VISIBILITIES ON THE COASTAL WATERS AND STRAIT OF JUAN DE FUCA WILL 

IMPROVE DURING THE DAY TODAY. DENSE FOG IS LIKELY TO RETURN TONIGHT 

BEFORE LIFTING ABOUT MIDDAY WED.



MEANWHILE...HIGH PRES OFFSHORE AND LOWER PRES E OF THE CASCADES WILL 

MAINTAIN ONSHORE FLOW OF VARYING STRENGTH THIS WEEK. WINDS MAY 

BRIEFLY REACH GALE FORCE OVER THE CENTRAL STRAIT OF JUAN DE FUCA 

THIS EVENING.



&&



.SEW WATCHES/WARNINGS/ADVISORIES...

WA...NONE.

PZ...DENSE FOG ADVISORY IN EFFECT UNTIL NOON TODAY FOR THE COASTAL

     WATERS AND WESTERN/CENTRAL STRAIT OF JUAN DE FUCA.



     SMALL CRAFT ADVISORY IN EFFECT FOR FOR THE CENTRAL STRAIT OF

     JUAN DE FUCA.



&&



$$



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FXUS66 KSEW 070435

AFDSEW



AREA FORECAST DISCUSSION 

NATIONAL WEATHER SERVICE SEATTLE WA

935 PM PDT TUE AUG 6 2013



.SYNOPSIS...HIGH PRESSURE ALOFT WITH WEAK ONSHORE FLOW WILL CONTINUE 

OVER THE PACIFIC NORTHWEST THROUGH THE WEEK. TEMPERATURES WILL 

MODERATE SLIGHTLY BY LATER IN THE WEEK BUT REMAIN NEAR OR A 

LITTLE ABOVE NORMAL. AN UPPER LEVEL LOW MAY TRIGGER SOME SHOWERS AND 

THUNDERSTORMS OVER THE CASCADES FRIDAY THROUGH EARLY NEXT WEEK. 



&&



.SHORT TERM...A WEAK UPPER LEVEL LOW OFF THE NORTHERN CALIFORNIA 

COAST IS HELPING TO MAINTAIN A RIDGE OF HIGH PRESSURE THAT EXTENDS 

FROM UTAH NORTHWESTWARD INTO WESTERN WASHINGTON. AT THE SURFACE...A 

RIDGE OF HIGH PRESSURE IS OVER THE OFFSHORE WATERS ALONG 130W WHILE 

LOWER PRESSURE SITS OVER SOUTHEASTERN WASHINGTON. THE WEATHER 

PATTERN WILL CHANGE LITTLE THROUGH THURSDAY OR FRIDAY...EXCEPT FOR 

PERHAPS A SLIGHT WEAKENING WITH TIME OF THE UPPER LEVEL RIDGE OVER 

THE AREA AND A SLIGHT INCREASE IN THE DEPTH OF THE MARINE LAYER AND 

THE STRENGTH OF THE ONSHORE FLOW.



SHALLOW FOG AND STRATUS HAS SPREAD ONTO THE COAST AND IS STARTING TO 

STREAM EASTWARD THROUGH THE STRAIT OF JUAN DE FUCA. EXPECT THE 

COVERAGE OF FOG AND STRATUS WEDNESDAY MORNING TO BE SIMILAR TO WHAT 

WAS SEEN THIS MORNING...GENERALLY IN THROUGH THE CHEHALIS GAP TO THE 

FAR SOUTH PUGET SOUND AND INTO THE ADMIRALTY INLET ZONE AND COASTAL 

PORTIONS OF THE NORTH INTERIOR ZONES. LIKE TODAY...STRATUS AND FOG 

WILL BURN BACK TO THE COASTLINE DURING THE MORNING HOURS. 500 MB 

HEIGHTS ON WEDNESDAY DROP ABOUT 10 METERS WHILE 850 MB TEMPERATURES 

DROP 1-2 DEG C. BASED ON THE CONTINUED WARM TEMPERATURES ALOFT AND 

ONLY LIGHT ONSHORE FLOW...AN EVENING UPDATE WAS MADE TO INCREASE THE 

FORECAST HIGH TEMPERATURES FOR WEDNESDAY TO ABOUT A DEGREE OR SO 

LOWER THAN TODAY IN THE CENTRAL PUGET SOUND AREA.



THURSDAY WILL LIKELY SEE A 2-3 DEGREES ADDITIONAL COOLING AS THE 

RIDGE OVER THE AREA SLOWLY WEAKENS.



THE NEGATIVE TILT RIDGE CONTINUES OVER THE AREA INTO FRIDAY BUT THE 

MID LEVEL FLOW BECOMES A BIT MORE SOUTHEASTERLY AS THE UPPER LOW OFF 

NORTHERN CALIFORNIA STARTS SLOWLY LIFTING NORTHWARD. LIFTED INDICES 

GO SUB ZERO ALONG THE CASCADE CREST BY LATE FRIDAY AFTERNOON/EVENING 

SUGGESTING SOME CUMULUS FORMATION AND PERHAPS A SLIGHT CHANCE OF 

THUNDERSTORMS. ALBRECHT



.LONG TERM...FROM THE PREVIOUS LONG TERM DISCUSSION...THE UPPER 

LEVEL LOW WHICH WAS STALLED ALL WEEK NEAR THE NRN CA COAST WILL 

BEGIN TO SLOWLY LIFT NWD FRIDAY NIGHT AND SATURDAY. SE FLOW WILL 

BECOME MORE PRONOUNCED OVER WRN WA WITH MID/UPPER LEVEL MOISTURE 

ADVECTION INTO WRN WA. BOTH THE GFS/ECMWF LIFT THE LOW NWD OFF THE 

WA COAST BY LATE IN THE WEEKEND. THIS KEEPS SLY OR SE FLOW WITH SOME 

INSTABILITY OVER THE AREA. DECIDED TO EXTEND THE THREAT OF 

THUNDERSTORMS TO THE OLYMPICS IN ADDITION TO THE CASCADES. BOTH 

SURFACE BASED AND ELEVATED INSTABILITY COULD BE ENOUGH FOR 

THUNDERSTORMS OVER THE LOWLANDS ESPECIALLY IF THE UPPER LOW DOES IN 

FACT LIFT NWD OFFSHORE PRODUCING DIFFLUENT FLOW OVER WRN WA. THE 

TRACK OF THE LOW IS STILL A BIT UNCERTAIN AS IS THE TIMING SO I HAVE 

OPTED TO LEAVE LOWLAND THUNDERSTORMS OUT OF THE FORECAST FOR NOW. 

MERCER



&&



.AVIATION...AN UPPER RIDGE WILL REMAIN OVER THE REGION THRU WED FOR 

CONTINUED WLY FLOW ALOFT. WEAK LOW LEVEL ONSHORE FLOW WILL PERSIST. 

THE AIR MASS WILL BECOME WEAKLY UNSTABLE OVER THE OLYMPIC RANGE IN 

THE AFTERNOON FOR A FEW MDT CU OR TCU.



MEANWHILE...LIFR CIGS AND/OR VSBYS WERE PRESENT ON THE COAST THIS 

EVENING. TOPS WERE RUNNING NEAR 1K FT PER THE SATELLITE DERIVED 

CLOUD THICKNESS PRODUCT. EXPECT LOW STRATUS/FOG COVERAGE TO BE ABOUT 

THE SAME AS OR SLIGHTLY LESS WED MORNING THAN TUE MORNING.  



KSEA...VFR CONDITIONS ARE EXPECTED TO PERSIST OVER THE TERMINAL THRU 

WED MORNING.



&&



.MARINE...

WIDESPREAD DENSE FOG ON THE COASTAL WATERS AND PARTS OF THE STRAIT 

OF JUAN DE FUCA WILL LIFT ABOUT MIDDAY WED BUT AREAS OF DENSE FOG 

WILL LIKELY PERSIST THROUGH THE AFTERNOON...ESPECIALLY ON THE 

COASTAL WATERS. THE VISIBILITY WAS BELOW 700 FEET IN SOME AREAS ON 

THE COASTAL WATERS THIS EVENING. 



MEANWHILE...HIGH PRES OFFSHORE AND LOWER PRES E OF THE CASCADES WILL 

CONTINUE THE REST OF THIS WEEK FOR ONSHORE FLOW OF VARYING STRENGTH.



&&



.SEW WATCHES/WARNINGS/ADVISORIES...

WA...NONE.

PZ...SMALL CRAFT ADVISORY IN EFFECT CENTRAL AND EASTERN STRAIT OF

      JUAN DE FUCA.

     DENSE FOG ADVISORY IN EFFECT TIL NOON WED FOR COASTAL

      WATERS AND MUCH OF THE STRAIT OF JUAN DE FUCA.





&&



$$



WWW.WEATHER.GOV/SEATTLE



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FXUS66 KSEW 071032

AFDSEW



AREA FORECAST DISCUSSION 

NATIONAL WEATHER SERVICE SEATTLE WA

300 AM PDT WED AUG 7 2013



.SYNOPSIS...HIGH PRESSURE ALOFT AND WEAK ONSHORE LOW LEVEL FLOW WILL 

CONTINUE FOR WESTERN WASHINGTON THROUGH THE WEEK. TEMPERATURES WILL 

MODERATE SLIGHTLY BUT REMAIN NEAR OR A LITTLE ABOVE NORMAL. AN UPPER 

LEVEL LOW MAY TRIGGER SOME SHOWERS AND THUNDERSTORMS OVER THE 

CASCADES FRIDAY THROUGH EARLY NEXT WEEK. 



&&



.SHORT TERM...AN UPPER LEVEL RIDGE REMAINS OVER THE REGION WITH WEAK 

WESTERLY FLOW ALOFT OVER WESTERN WASHINGTON. WEAK ONSHORE FLOW 

CONTINUES AT LOW LEVELS. MARINE STRATUS WITH BASES MAINLY BELOW 500 

FT IS MOVING INLAND FROM THE COAST...BOTH THROUGH THE STRAIT OF JUAN 

DE FUCA AND THE LOWER CHEHALIS VALLEY. IN OTHER WORDS THE SITUATION 

EARLY THIS MORNING IS REMARKABLY SIMILAR TO THE SITUATION 24 HOURS 

AGO.



AND THERE WILL BE LITTLE CHANGE TODAY TOO. THE UPPER RIDGE WILL 

REMAIN IN PLACE WITH 500 MB HEIGHTS OVER THE FORECAST AREA AROUND 

5820 METERS AND WEAK ONSHORE FLOW. LOW STRATUS WILL BURN OFF MID 

MORNING THROUGH EARLY AFTERNOON FOR SUNSHINE AND TEMPERATURES 

SEVERAL DEGREES ABOVE NORMAL.



MODELS SHOW THE UPPER RIDGE WEAKENING SLIGHTLY WEDNESDAY NIGHT AND 

THURSDAY...AS THE WEAK UPPER LOW CURRENTLY OFFSHORE OF NORTHERN 

CALIFORNIA MOVES EAST TO THE COAST. THE 500 MB HEIGHTS OVER WESTERN 

WASHINGTON WILL FALL TO AROUND 5800 METERS...THE AIR MASS WILL COOL 

1 OR 2 DEGREES CELSIUS...AND ONSHORE FLOW WILL INCREASE A BIT. THIS 

IS A PRETTY SUBTLE CHANGE REALLY. MARINE CLOUDINESS SHOULD BE A BIT 

MORE WIDESPREAD OVER THE INTERIOR LOWLANDS BUT STILL GIVE WAY TO 

AFTERNOON SUNSHINE...AND HIGHS WILL COOL A BIT BUT REMAIN ABOVE 

NORMAL.



THE UPPER LOW WILL REMAIN NEAR THE NORTHERN CALIFORNIA COAST 

THURSDAY NIGHT AND FRIDAY...AND THE UPPER RIDGE WILL WEAKEN A BIT 

MORE. MORNING CLOUDS SHOULD GIVE WAY TO AFTERNOON SUNSHINE ONCE 

AGAIN WITH HIGH TEMPERATURES JUST A COUPLE DEGREES COOLER. ISOLATED 

SHOWERS AND THUNDERSTORMS COULD DEVELOP OVER THE CASCADES FRIDAY 

AFTERNOON AND EVENING...AS THE UPPER LOW MARGINALLY DESTABILIZES THE 

AIR MASS ALOFT AND INJECTS SOME MID AND HIGH LEVEL MOISTURE INTO THE 

AREA.   MCDONNAL  



.LONG TERM...THE UPPER LOW WILL BE ALONG THE SOUTHERN OREGON COAST 

SATURDAY AND MOVE SLOWLY NORTH-NORTHWEST TO A POSITION OVER THE 

WASHINGTON OFFSHORE WATERS ON MONDAY. THE UPPER RIDGE AXIS WILL 

REMAIN EAST OF THE CASCADES. SO SOUTHERLY FLOW ALOFT WILL CONTINUE 

OVER WESTERN WASHINGTON DURING THIS PERIOD...WITH A SLIGHTLY 

UNSTABLE AIR MASS ALOFT AND A CHANCE FOR THUNDERSTORMS IN THE 

MOUNTAINS. MODEL TIMING IS UNCERTAIN...BUT THE LOW WILL PROBABLY BE 

FAR ENOUGH NORTH ON TUESDAY TO ELIMINATE THE THUNDERSTORM THREAT. 





FOR THE WESTERN WASHINGTON LOWLANDS...THE ONSHORE FLOW AND MARINE 

INFLUENCE COULD BE A LITTLE STRONGER. BUT THE TREND OF NIGHT AND 

MORNING LOW CLOUDS WITH AFTERNOON SUNSHINE SHOULD CONTINUE. HIGH 

TEMPERATURES WILL BE NEAR OR SLIGHTLY ABOVE NORMAL.   MCDONNAL



&&



.AVIATION...AN UPPER RIDGE WILL REMAIN OVER THE REGION. CONTINUED 

LIGHT WLY FLOW ALOFT AND LOW LEVEL ONSHORE FLOW. THE AIR MASS WILL 

BECOME WEAKLY UNSTABLE OVER THE OLYMPICS THIS AFTERNOON FOR THE 

POSSIBILITY OF A FEW CLOUD BUILDUPS BUT THE RISK OF A TSTM WILL BE 

LOW. 



MEANWHILE...LIFR CIGS AND/OR VSBYS WERE PRESENT OVER PARTS OF THE 

AREA EARLY THIS MORNING. PER THE SATELLITE DERIVED CLOUD THICKNESS 

PRODUCT...TOPS WERE RUNNING ABOUT 1K FT. THE COVERAGE WAS NEARLY 

SIMILAR TO WHAT IT WAS THE SAME TIME YESTERDAY. LOOK FOR THE LOW 

STRATUS/FOG TO DISSIPATE  BETWEEN 1700 AND 1900 UTC...LATEST OVER 

THE COAST.   



KSEA...VFR CONDITIONS ARE EXPECTED TODAY.



&&



.MARINE...

THE VISIBILITY THIS MORNING WAS A QUARTER MILE OR LESS ON MUCH OF 

THE COASTAL WATERS /WHERE FOG HORNS COULD BE HEARD/ AND STRAIT OF 

JUAN DE FUCA. THERE WERE ALSO AREAS OF POOR VISIBILITY ON THE 

ADMIRALTY INLET AND SOUTH OF THE SAN JUANS EARLY THIS MORNING. LOOK 

FOR THE DENSE FOG TO LIFT ABOUT MIDDAY TODAY BUT AREAS OF DENSE FOG 

WILL CONTINUE INTO THIS AFTERNOON...ESPECIALLY ON THE COASTAL 

WATERS. EXPECT DENSE FOG TO REDEVELOP TONIGHT...BECOMING WIDESPREAD 

AGAIN ON THE COASTAL WATERS AND WEST ENTRANCE TO THE STRAIT OF JUAN 

DE FUCA.



MEANWHILE...PERSISTENT HIGH PRES OFFSHORE AND LOWER PRES E OF THE 

CASCADES WILL KEEP THE FLOW ONSHORE THROUGH THIS WEEKEND. THERE IS A 

CHANCE THAT WINDS WILL REACH GALE FORCE OVER THE CENTRAL STRAIT OF 

JUAN DE FUCA THIS EVENING.



&&



.SEW WATCHES/WARNINGS/ADVISORIES...

WA...NONE.

PZ...DENSE FOG ADVISORY IN EFFECT TIL NOON TODAY FOR THE COASTAL

     WATERS AND STRAIT OF JUAN DE FUCA.



     SMALL CRAFT ADVISORY IN EFFECT FOR THE CENTRAL AND EASTERN

     STRAIT OF JUAN DE FUCA.



     GALE WATCH IN EFFECT THIS EVENING FOR THE CENTRAL STRAIT OF

     JUAN DE FUCA.



&&



$$



YOU CAN SEE AN ILLUSTRATED VERSION OF THE FORECAST DISCUSSION AT 

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FXUS66 KSEW 171050

AFDSEW



AREA FORECAST DISCUSSION

NATIONAL WEATHER SERVICE SEATTLE WA

350 AM PDT THU OCT 17 2013



.SYNOPSIS...A STRONG UPPER RIDGE JUST OFFSHORE WILL BRING RAIN-FREE 

WEATHER TO WESTERN WASHINGTON FOR THE NEXT WEEK. AREAS OF FOG WILL 

COVER MUCH OF THE LOWLANDS DURING THE LATE NIGHT AND MORNING 

HOURS...BUT SKIES WILL BE MAINLY CLEAR OTHERWISE.



&&



.SHORT TERM...A STRONG BLOCKING UPPER HIGH WILL CONTINUE OVER THE NE 

PAC THROUGH SAT...WITH THE RIDGE AXIS PERSISTING NEAR 130W-135W. 

THIS IS ACCOMPANIED BY A VERY STABLE AIR MASS AND DRY AIR ALOFT. 

OVER THE LOWLANDS...LOW-LEVEL MOISTURE WILL PERSIST THROUGH 

SAT...POSING A RISK OF MAINLY OVERNIGHT AND MORNING FOG AND LOW 

STRATUS. WITH THE UPPER RIDGE AXIS SO CLOSE...WINDS WILL BE ON THE 

LIGHT SIDE.



AS FOR TODAY...FOG IR IMAGERY CURRENTLY SHOWS FAIRLY WIDESPREAD 

COVERAGE OF LOW STRATUS OVER BOTH THE INTERIOR AND COASTAL LOWLANDS 

EARLY THIS MORNING. EXPECTING THIS TO BE FAIRLY SLOW TO BURN OFF 

TODAY...BUT MOST PLACES WILL CLEAR OUT BY LATE AFTN. THE MOUNTAINS 

ABOVE 1000-1500 FEET WILL BE SUNNY FROM START TO FINISH TODAY.



FOR AIR QUALITY...GIVEN THE SETUP...IT IS NOT SURPRISING THAT QUITE 

A FEW SENSORS AROUND THE PUGET SOUND REGION ARE IN THE "UNHEALTHY 

FOR SENSITIVE GROUPS" CATEGORY. LOW CLOUDS TODAY WILL KEEP THE LOWER 

ATMOSPHERE COOLER AND MORE STABLE...KEEPING VERTICAL MIXING TO A 

MINIMUM. A NORTH WIND TO 10 MPH MAY HELP WITH HORIZONTAL TRANSPORT 

THIS AFTN...BUT WINDS BECOME EVEN LIGHTER ON FRI AND SAT.   HANER



.LONG TERM...MODELS ARE TENACIOUSLY STUBBORN AT KEEPING THE BLOCKING 

UPPER HIGH IN PLACE OVER THE NE PAC...SO A PERSISTENCE FORECAST WITH 

LITTLE DAY-TO-DAY CHANGE IS THE WAY TO GO. THIS AMOUNTS TO OVERNIGHT 

AND MORNING FOG AND LOW STRATUS OVER THE LOWLANDS...WITH MOSTLY 

SUNNY AFTERNOONS. COLD NIGHTS ARE EXPECTED UNDER THE DRY AIR MASS 

ALOFT. THE STABLE AIR MASS WITH LIGHT WINDS WILL CONTINUE AIR 

QUALITY CONCERNS. 



BOTH THE GFS AND ECMWF BRING A WEAKNESS IN THE RIDGE ACROSS THE PAC 

NW AROUND TUE OR WED OF NEXT WEEK...BUT NEITHER MODEL SHOWS 

APPRECIABLE PRECIP. SUCH A WEAKNESS WOULD TRY TO PUSH SOME MARINE 

STRATUS INLAND TOWARD THE MIDDLE OF NEXT WEEK...DIMMING THE 

PROSPECTS FOR AFTERNOON CLEARING OVER THE LOWLANDS IF THE WEAKNESS 

IN THE RIDGE MATERIALIZES. BEYOND DAY 7...BOTH THE GFS AND ECMWF 

RE-STRENGTHEN THE UPPER HIGH AGAIN FOLLOWING THE MID-WEEK 

WEAKNESS.      HANER



&&



.AVIATION...A LARGE STRONG UPPER LEVEL RIDGE CENTERED OFFSHORE ALONG 

130W WILL GIVE DRY NORTHERLY FLOW ALOFT OVER W WA THROUGH 12Z 

FRIDAY. THE AIR MASS WILL REMAIN DRY AND STABLE...BUT A STRONG 

SURFACE BASED TEMPERATURE INVERSION WILL CONTINUE TRAPPING 

WIDESPREAD LOW STRATUS AND AREAS OF FOG OVER MAINLY THE INTERIOR 

LOWLANDS. IFR CIGS AND VISIBILITY ARE EXPECTED THROUGH ROUGHLY 19Z. 

THIS MORNING SEEMS TO BE TRENDING TOWARD MORE OF A LOW STRATUS EVENT 

RATHER THAN WIDESPREAD DENSE FOG. STRATUS TOPS APPEAR TO BE 1500 TO 

2300 FEET...SO THE DEEPER LAYER WILL PROBABLY DELAY CLEARING IN SOME 

AREAS TO 20Z-23Z. 



KSEA...TRICKY FORECAST FOR THIS MORNING SO CONFIDENCE IS NOT VERY 

HIGH. STRATUS HAS FILLED AT OVC010 BUT THE SURFACE TEMP DEW POINT IS 

STILL RUNNING 5 DEGREES F. THE NEW CLOUD THICKNESS SATELLITE PRODUCT 

HAS THE STRATUS LAYER ABOUT 1200 FEET THICK...PUTTING TOPS AROUND 

2200 FEET. I AM LEANING TOWARD MORE OF A STRATUS EVENT THIS MORNING 

BUT THERE IS STILL SOME POTENTIAL FOR A SHORTER PERIOD OF 1/2SM FG. 

THAT IS PROBABLY THE LEAST CONFIDENT PART OF THE FORECAST. WITH TOPS 

PRESUMABLY STILL OVER 2000 FEET...BURN-OFF WILL LIKELY BE LATER THAN 

19Z...SO WILL GUESSTIMATE AROUND 22Z. SURFACE WINDS WILL REMAIN 

LIGHT BUT GENERALLY FAVOR N. KAM



&&



.MARINE...SURFACE RIDGES OVER SE B.C. AND OFFSHORE ALONG ROUGHLY 

135W WILL REMAIN IN PLACE THROUGH FRIDAY...WHILE A WEAK SURFACE 

TROUGH CONTINUES OVER W WA. THIS WILL KEEP WINDS WEAK AND FAVORING A 

NORTHERLY DIRECTION. THE OFFSHORE SURFACE RIDGE WILL BECOME MORE 

DOMINANT THIS WEEKEND LEADING TO WEAK ONSHORE FLOW. 



THIS MORNING IS TRENDING TOWARD MORE OF A LOW STRATUS EVENT RATHER 

THAN FOG...BUT THERE WILL PROBABLY STILL BE SOME PATCHY DENSE FOG 

AROUND THE INLAND WATERS THIS MORNING. KAM



&&





.SEW WATCHES/WARNINGS/ADVISORIES...

WA...NONE.

PZ...NONE.



&&



$$



YOU CAN SEE AN ILLUSTRATED VERSION OF THE FORECAST DISCUSSION AT 

WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML








FXUS66 KSEW 231047

AFDSEW



AREA FORECAST DISCUSSION

NATIONAL WEATHER SERVICE SEATTLE WA

345 AM PDT WED OCT 23 2013



.SYNOPSIS...STRONG HIGH PRESSURE ALOFT WILL REMAIN OVER THE REGION 

THROUGH SATURDAY...LEADING TO CLEAR AND MILD CONDITIONS IN THE 

MOUNTAINS AND PERSISTENT CLOUDS AND FOG OVER THE INTERIOR LOWLANDS. 

LOW LEVEL OFFSHORE FLOW WILL RESULT IN SUNNY WARM WEATHER ALONG THE 

COAST TODAY...BUT THE OFFSHORE FLOW WILL WEAKEN TONIGHT AND THURSDAY 

WITH LOW CLOUDS AND FOG RETURNING TO THE COAST. 



&&



.SHORT TERM...SATELLITE IMAGERY SHOWS UPPER LEVEL RIDGE ALONG THE 

COAST STILL HOLDING STRONG KEEPING WEATHER SYSTEMS AWAY FROM WESTERN 

WASHINGTON. FOG/STRATUS IMAGERY SHOWS FOG HAS REFORMED OVER THE MUCH 

OF THE INTERIOR LOWLANDS WITH THE FOG MAKING A MOVE WEST THROUGH THE 

CHEHALIS VALLEY TOWARDS THE CENTRAL COAST. TEMPERATURES WERE IN THE 

40S AT 3 AM.



ONCE AGAIN THE FORECAST PROBLEM THIS MORNING IS HOW MUCH IF ANY 

CLEARING OF THE FOG AND LOW CLOUDS WILL THERE BE THIS AFTERNOON. 

OFFSHORE GRADIENTS STILL INTACT ACROSS WESTERN WASHINGTON BE THE 

GRADIENT HAS WEAKENED A LITTLE IN THE LAST FEW HOURS. WITH THE 

CLEARING TUESDAY AFTERNOON THE LOW LEVEL MOISTURE IS A LITTLE 

THINNER THIS MORNING WITH CLOUD THICKNESS IMAGERY PUTTING THE TOPS 

IN THE 800 TO 1200 FOOT RANGE. EVEN WITH THE WEAKER OFFSHORE FLOW 

TODAY WITH THE MOISTURE LAYER THIS SHALLOW WILL GO FOR ANOTHER ROUND 

OF AFTERNOON CLEARING FOR THE INTERIOR. TEMPERATURES WILL GET INTO 

THE MID AND UPPER 50S FOR THE MOST PART. THE COAST WILL ONCE AGAIN 

BE THE WARM SPOT IN THE LOWLANDS BUT WITH THE WEAKER OFFSHORE FLOW 

WILL LOWER HIGH TEMPERATURES BACK DOWN INTO THE 60S FOR THE NORTH 

COAST.  



IN THE MEANTIME...WITH THE CLEARING YESTERDAY FOG OVER PARTS OF THE 

AREA IS THICKER THIS MORNING. ALL OF THE OBSERVATIONS IN THE CENTRAL 

PUGET SOUND REPORTING A QUARTER MILE OR LESS AT 3 AM. WILL ISSUE A 

DENSE FOG ADVISORY UNTIL 18Z FOR THE SEATTLE...TACOMA...EVERETT AND 

VICINITY.



UPPER LEVEL RIDGE REMAINING OVER THE AREA THROUGH FRIDAY WITH A WEAK 

UPPER LEVEL LOW EMBEDDED IN THE RIDGE WOBBLING AROUND OFFSHORE. THIS 

FEATURE DOES NOT LOOK LIKE IT WILL PRODUCE ANY WEATHER. SMALL 

CHANGES IN THE LOWER LEVELS...LOW LEVEL OFFSHORE FLOW BECOMING LIGHT 

TO SLIGHTLY ONSHORE TONIGHT INTO THURSDAY...WILL RESULT IN MORE 

WIDESPREAD LOW CLOUDS AND FOG OVERNIGHT INTO THURSDAY MORNING. WITH 

THE LIGHT LOW LEVEL FLOW THE CHANCES FOR AFTERNOON SUNSHINE ON 

THURSDAY WILL BE REDUCED.   



LITTLE CHANGE IN THE PATTERN THURSDAY NIGHT INTO FRIDAY WITH THE LOW 

LEVEL FLOW REMAINING LIGHT KEEPING THE CLOUDY AND FOGGY FORECAST 

INTACT. 



AS HAS BEEN THE CASE FOR THE LAST FEW DAYS WEATHER IN THE MOUNTAINS 

WILL CONTINUE TO BE SUNNY AND WARM DURING THE DAY INTO FRIDAY WITH 

AFTERNOON TEMPERATURES IN THE 60S COMMON. FELTON



.LONG TERM...LITTLE CHANGE IN THE FORECAST FOR SATURDAY WITH THE 

UPPER LEVEL RIDGE REMAINING IN PLACE AND LIGHT LOW LEVEL FLOW. 

MODELS WERE HAVING TOUGH TIME ON PREVIOUS RUNS COMING TO A CONSENSUS 

WITH THE SHORTWAVE MOVING DOWN THE BACKSIDE OF THE RIDGE FOR LATER 

SATURDAY NIGHT INTO SUNDAY. THE 00Z RUNS ARE IN PRETTY GOOD 

AGREEMENT WITH THE SHORTWAVE GOING BY TO THE EAST SUNDAY. CURRENT 

FORECAST HAS A CHANCE OF SHOWERS IN THE CASCADES WITH THIS FEATURE. 

LOOK FOR THIS TO BE TAKEN OUT OF THE FORECAST IF ANOTHER MODEL RUN 

OR TWO AGREES WITH THE 00Z SOLUTION. MODELS ALSO IN GOOD AGREEMENT 

WITH INCREASING NORTHERN SURFACE GRADIENTS LATER SUNDAY INTO MONDAY. 

STRONG ENOUGH TO SCOUR THE LOW LEVEL MOISTURE OUT OF THE LOWLANDS. 

WITH THE COOL DRY AIR MOVING INTO THE REGION MONDAY AND TUESDAY WILL 

STAY WITH THE IDEA OF SUNNY SKIES WITH HIGHS NEAR OR JUST A COUPLE 

OF DEGREES BELOW NORMAL FOR MONDAY AND TUESDAY. FELTON



&&



.AVIATION...WIDESPREAD FOG IN THE LOWLANDS THROUGH THE MORNING 

SHOULD GIVE WAY TO AREAS OF CLEARING SIMILAR TO YESTERDAY IN THE 

AFTERNOON. AN UPPER HIGH IS CENTERED OVER WA WITH LIGHT WINDS ALOFT. 

THERE IS DRY WARM AIR ALOFT WITH AREAS OF LOW LEVEL MOISTURE TRAPPED 

UNDER A STRONG INVERSION...AND THE FOG IS DENSE IN SOME AREAS. 

PRESSURE GRADIENTS ARE LIGHT OFFSHORE. 



KSEA...LOW VSBY FOG AND CALM THIS MORNING...BUT A GOOD CHANCE AGAIN 

TO SEE SUNSHINE DEVELOP THIS AFTERNOON. THE WEATHER PATTERN HAS NOT 

CHANGED WITH WARM DRY AIR ALOFT...LIGHT PRESSURE GRADIENTS...AND A  

STRONG INVERSION. OVERALL THE RVR HAS BEEN LOWER OVERNIGHT AND A 

DENSE FOG ADVISORY IS UP FOR THE METRO AREA THIS MORNING. 



&&



.MARINE...LIGHT OFFSHORE FLOW WITH WIDESPREAD FOG. THE FORECAST FOR 

CLEARING OVER THE LAND AREAS THIS AFTERNOON MIGHT NOT ACTUALLY WORK 

OUT FOR MARINE AREAS SINCE ALL THE OFFSHORE GRADIENTS ARE WEAKER 

THIS MORNING THAN THEY WERE YESTERDAY AT THIS TIME AND THERE IS MUCH 

MORE FOG OVER THE COASTAL WATERS THAN THERE WAS EARLY YESTERDAY. THE 

SMALL CRAFT ADVISORY FOR THE AREA NEAR THE WEST ENTRANCE LOOKS 

PRETTY MARGINAL BUT WILL LEAVE IT UP FOR THE MORNING...OFFSHORE FLOW 

DOES TEND TO PEAK IN THE MORNING AND THE WIND AT TATOOSH MAY 

INCREASE A BIT THROUGH DAYBREAK.





&&



.SEW WATCHES/WARNINGS/ADVISORIES...

WA...NONE.

PZ...SMALL CRAFT ADVISORY COASTAL WATERS CAPE FLATTERY TO JAMES 

ISLAND OUT 10 NM AND WEST ENTRANCE STRAIT OF JUAN DE FUCA.



&&



$$



WWW.WEATHER.GOV/SEATTLE



YOU CAN SEE AN ILLUSTRATED VERSION OF THE FORECAST DISCUSSION AT 

WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML














FXUS66 KSEW 241026

AFDSEW



AREA FORECAST DISCUSSION

NATIONAL WEATHER SERVICE SEATTLE WA

326 AM PDT THU OCT 24 2013



.SYNOPSIS...STRONG HIGH PRESSURE ALOFT WILL REMAIN OVER THE REGION 

THROUGH SATURDAY...LEADING TO CLEAR AND MILD CONDITIONS IN THE 

MOUNTAINS AND PERSISTENT LOW CLOUDS AND FOG OVER BOTH THE INTERIOR 

AND COASTAL LOWLANDS. A CANADIAN COLD FRONT IS EXPECTED TO REACH 

WESTERN WASHINGTON ON SUNDAY OR SUNDAY NIGHT...USHERING IN A MUCH 

DRIER AIR MASS AND BRINGING AN END TO THE PERSISTENT FOG PATTERN.



&&



.SHORT TERM...FOG PRODUCT SATELLITE IMAGERY SHOWED THE EFFECTS OF 

WEAK ONSHORE OVERNIGHT AS LOW LEVEL MOISTURE ALONG THE COAST SURGED 

INLAND THROUGH THE STRAIT OF JUAN DE FUCA AND UP THE LOWER CHEHALIS 

VALLEY. THE STRONG LOW LEVEL SUBSIDENCE INVERSION REMAINS IN 

PLACE...TRAPPING MOISTURE NEXT TO THE SURFACE. SO FAR AS OF 1015Z 

THE NEW SATELLITE LOW CLOUD THICKNESS PRODUCT IS INDICATING 

THICKNESSES ARE STILL FAIRLY SHALLOW IN SPOTS...NEAR 1000 FEET LIKE 

YESTERDAY...AND SOME OBS AND LOCAL WEB CAMERAS AGREE. BASED ON THIS 

I WILL CROSS THE FINGERS AND MAKE A LAST MINUTE CHANGE AND GO WITH 

PARTLY SUNNY FOR THIS AFTERNOON...FIGURING A BURN-OFF MID TO LATE 

THIS AFTERNOON.  



THE PERSISTENT STRONG UPPER LEVEL RIDGE WILL REMAIN OVER THE REGION 

THROUGH SATURDAY WITH THE LOWLAND FOG AND LOW CLOUDS PROBLEM LIKELY 

CONTINUING FRIDAY AND SATURDAY. HOWEVER THERE IS A CHANCE THAT A 

WANDERING DRY UPPER LEVEL LOW...CURRENTLY OFFSHORE NEAR 

48N/131W...WILL MOVE OVER W WA FRIDAY AFTERNOON AND CONTRIBUTE TO A 

BREAKUP OF THE STRATUS AND FOG. THERE IS POTENTIAL HERE BUT THE 

OUTCOME IS UNCERTAIN. THE MODELS HAVE BEEN INCONSISTENT IN 

FORECASTING THE TRACK OF THE LOW...DESPITE GOOD 00Z ECMWF/GFS 

AGREEMENT. THE COLD AIR ALOFT MAY NOT EXTEND DOWN CLOSE ENOUGH TO 

THE SURFACE TO SUBSTANTIALLY DISTURB THE SUBSIDENCE INVERSION. THE 

EFFECTS OF THE LOW MAY ONLY BE PARTIAL IN THAT THE BOUNDARY LAYER 

DEEPENS A LITTLE MORE ALLOWING THE FOG TO LIFT INTO STRATUS. DUE TO 

THE UNCERTAINTY...FOR NOW THE FORECASTS HAVE BEEN LEFT AS IS...GOING 

WITH THE CLOUDY FOGGY SOLUTION. SOME DRIZZLE MAY DEVELOP W OF PUGET 

SOUND FRIDAY MORNING AS A RESULT OF THE LOW. 



EVEN IF THE STRATUS AND FOG MIX OUT ON FRIDAY...FOG WILL REFORM 

AGAIN FRIDAY NIGHT...LEADING TO ANOTHER EPISODE ON SATURDAY. NO 

CHANGE IN TEMPERATURE RANGES IS EXPECTED...UNLESS THE STRATUS AND 

FOG MIX OUT. KAM



.LONG TERM...THE GFS/ECMWF HAVE BEEN IN BETTER AGREEMENT WITH THE 

STRONG BUT DRY UPPER LEVEL SHORTWAVE TROUGH THAT MOVES S ACROSS THE 

AREA ON SUNDAY. COLDER AIR ALOFT AND BREEZY N WINDS WILL MIX OUT ALL 

THE SHALLOW LOW LEVEL MOISTURE AND PRETTY MUCH DESTROY THE 

SUBSIDENCE INVERSION. THE DRIER AIR MASS WILL LINGER THROUGH EARLY 

NEXT WEEK FOR SUNSHINE MONDAY AND TUESDAY...AND COOLER MORNING 

TEMPERATURES TUESDAY AND WEDNESDAY. A CHANGE BACK TO WESTERLY FLOW 

ALOFT AND PERIODIC FRONTAL SYSTEMS MAY TAKE PLACE AROUND MID NEXT 

WEEK. KAM



&&



.AVIATION...A STRONG UPPER LEVEL RIDGE REMAINS OVER THE PACIFIC 

NORTHWEST TODAY WITH LIGHT FLOW ALOFT. LOW LEVEL FLOW TRANSITIONING 

TO LIGHT ONSHORE TODAY. THE AIR MASS IS DRY EXCEPT FOR A MOIST 

SHALLOW SURFACE-BASED LAYER. 



SATELLITE IMAGERY SHOWS LOW STRATUS AND FOG OVER MOST OF THE 

LOWLANDS. CLOUD THICKNESS IMAGERY PUTS THE LAYER BETWEEN 800 AND 

1200 FEET THICK...SIMILAR TO WEDNESDAY MORNING. OFFSHORE GRADIENTS 

OVER THE INTERIOR HAVE WEAKENED AND ARE NEARLY FLAT BUT THERE STILL 

IS -2 MB ACROSS THE CASCADES AND THE EASTERLIES IN THE MOUNTAINS ARE 

STILL IN THE 10 TO 15 KNOT RANGE. THE WEAKENING OF THE OFFSHORE 

GRADIENT IS WORRISOME BUT WITH KPAE STILL NOT REPORTING A CEILINGS 

THIS IS A GOOD INDICATION THE LAYER IS VERY THIN THIS MORNING. WILL 

CONTINUE WITH THE IDEA OF CEILINGS BELOW 200 FEET AND VISIBILITIES 

1/2 MILE OR LESS AT ALL OF THE TERMINALS EXCEPT KHQM THIS MORNING 

BUT WILL BE MORE OPTIMISTIC THIS AFTERNOON AND CLEAR THINGS OUT BY 

MID AFTERNOON FOR THE CENTRAL AND NORTHERN PUGET SOUND TERMINALS. 

CONDITIONS WILL DETERIORATE ONCE AGAIN LATER THIS EVENING INTO THE 

EARLY MORNING HOURS ON FRIDAY.



KSEA...VISIBILITY BOUNCING BETWEEN A QUARTER AND A HALF MILE THIS 

MORNING WITH CEILINGS 200 FEET OR LESS. TOPS LOOK TO BE LESS THAN 

1000 FEET THICK SO WILL GO FOR CONDITIONS IMPROVING MIDDAY WITH 

SKIES CLEARING OUT AROUND 21Z. LOW CLOUDS WITH VISIBILITIES BELOW A 

MILE RETURNING TO THE TERMINAL AROUND 06Z TONIGHT. LIGHT WINDS INTO 

FRIDAY MORNING. FELTON



&&



.MARINE...LIGHT LOW LEVEL FLOW BECOMING LIGHT ONSHORE TODAY.  

WIDESPREAD FOG WITH VISIBILITIES 1/4SM OR LESS WILL CONTINUE THROUGH 

THE MORNING HOURS. THE LIGHT ONSHORE FLOW PATTERN WILL REMAIN INTACT 

THROUGH SATURDAY NIGHT WITH WINDS 15 KT OR LESS. STRONGER NORTHEAST 

WINDS WILL DEVELOP ON SUNDAY AND PEAK ON MONDAY AS HIGH PRESSURE 

BUILDS OVER SOUTHERN BRITISH COLUMBIA. SMALL CRAFT ADVISORY WINDS 

ARE LIKELY OVER PARTS OF THE COASTAL WATERS...ENTRANCES TO THE 

STRAIT OF JUAN DE FUCA...AND NORTHERN INLAND WATERS AT THAT TIME. 

FELTON



&&



.SEW WATCHES/WARNINGS/ADVISORIES...

WA...NONE.

PZ...NONE.



&&



$$



YOU CAN SEE AN ILLUSTRATED VERSION OF THE FORECAST DISCUSSION AT 

WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML














FXUS66 KSEW 242145

AFDSEW



AREA FORECAST DISCUSSION

NATIONAL WEATHER SERVICE SEATTLE WA

245 PM PDT THU OCT 24 2013



.SYNOPSIS...STRONG HIGH PRESSURE ALOFT WILL REMAIN OVER THE REGION 

THROUGH SATURDAY...LEADING TO CLEAR AND MILD CONDITIONS IN THE 

MOUNTAINS AND PERSISTENT LOW CLOUDS AND FOG OVER BOTH THE INTERIOR 

AND COASTAL LOWLANDS. A CANADIAN COLD FRONT IS EXPECTED TO REACH 

WESTERN WASHINGTON ON SUNDAY...USHERING IN A MUCH DRIER AIR MASS AND 

BRINGING AN END TO THE PERSISTENT FOG PATTERN.



&&



.SHORT TERM...SHALLOW FOG CONTINUES TO COVER MUCH OF THE WESTERN WA 

LOWLANDS THIS AFTERNOON. THERE IS NOT ENOUGH MIXING TO ERODE THIS 

SHALLOW LAYER /UNLIKE YESTERDAY WHEN OFFSHORE GRADIENTS WERE 

STRONGER/. BUT THERE ARE A FEW HOLES LIKE KITSAP 

COUNTY...SHELTON...KPAE AND SAN JUANS. THOSE FEW LUCKY AREAS ARE 

SEEING SOME SUNRAYS WITH TEMPS IN THE 50S. ELSEWHERE IT IS CLOUDY 

AND STILL IN THE 40S. IT IS CLEAR AND SUNNY ABOVE 1000 FT. HURRICANE 

RIDGE AND PARADISE RANGER STATION ARE IN THE 60S. EXPECT THE FOG TO 

FILL BACK IN TONIGHT.  



THE RIDGE IS STILL IN PLACE ON FRI...BUT THERE IS A CAVEAT. THERE IS 

A COMPACT CLOSED UPPER LOW THAT WILL UNDERCUT THE RIDGE AND SETTLE 

OVER WESTERN WA. THIS FEATURE WILL DEEPEN THE FOG LAYER ON FRIDAY 

AND WE WILL LIKELY NOT BREAK OUT. THIS FEATURE WILL THEN SLOWLY EXIT 

ON SAT. SO EXPECT MORE CLOUDS AND COOLER CONDITIONS BOTH DAYS. 

HOWEVER...IT WILL STILL BE SUNNY AND MILD IN THE MOUNTAINS. 



A WEAK FRONT WILL CROSS THE AREA ON SUNDAY AND WE MAY FINALLY SEE 

SOME CLEARING THEN. MODELS SHOW THE UPPER TROUGH CLIPPING EASTERN WA 

WITH DRY WEATHER AGAIN WEST OF THE CASCADES. 33



.LONG TERM...DRY NORTHERLY FLOW WILL PREVAIL ACROSS WESTERN WA ON 

MONDAY FOR MORE BENIGN WEATHER. MODELS ARE SHOWING A E/NE PRES 

GRADIENT WHICH SHOULD KEEP THE LOW LEVEL AIR MASS DRIER - LESS 

CHANCES FOR FOG FORMATION. THE NORTH COAST AND WESTERN WHATCOM 

COUNTY MAY SEE WINDY NE WINDS FROM A FRASER OUTFLOW. 



THE UPPER RIDGE WILL FINALLY FLATTEN AND WEAKEN TUE AND WED WITH THE 

FLOW ALOFT BECOMING MORE ZONAL. A WEAK DISTURBANCE MAY BRING SOME 

LIGHT PRECIP TO THE REGION WED NIGHT OR THU. 33



&&



.AVIATION...A STRONG UPPER LEVEL RIDGE WILL REMAIN OVER THE PACIFIC 

NORTHWEST THROUGH TONIGHT GIVING STABLE CONDITIONS AND LIGHT FLOW 

ALOFT. IN THE LOWER LEVELS...A SUBSIDENCE INVERSION AROUND FL020 IS 

TRAPPING LOW LEVEL MOISTURE NEAR THE SURFACE. CHANGES WILL TAKE 

PLACE STARTING LATE TONIGHT AND FRIDAY MORNING AS A SMALL UPPER LOW 

OVER THE OFFSHORE WATERS DROPS SE ACROSS THE AREA. THIS WILL DEEPEN 

THE MOIST BOUNDARY LAYER SIGNIFICANTLY FRI AND FRI NIGHT.



FOG AND STRATUS IS QUITE SHALLOW THIS AFTERNOON. VISIBLE IMAGERY 

SHOWS THE LOW PLATEAU JUST SE OF KPAE AT ABOUT 500 FT...THE HILLS 

OF THE KITSAP PENINSULA ABOVE ABOUT 800 FT...AND CAPITOL PEAK W OF 

KOLM STICKING ABOVE THE FOG. THE GOES CLOUD THICKNESS PRODUCT SHOWS 

THICKEST FOG AROUND ADMIRALTY INLET AND PORT TOWNSEND AND AROUND 

SEATAC AIRPORT. EXPECT THE IMPROVING TREND TO CONTINUE THRU ABOUT 

SUNSET...THOUGH THE CLEARING WILL BE MUCH LESS THAN WHAT OCCURRED ON 

WED AFTERNOON. FOG WILL RAPIDLY INCREASE AGAIN AROUND 06Z TONIGHT.



AN UPPER LOW SITTING OFF CENTRAL VANCOUVER ISLAND WILL DROP SE INTO 

W WA ON FRI. THE NAM12 TIME SECTION FOR SEATTLE SHOWS THE INVERSION 

LIFTING AND WEAKENING STARTING AROUND 10Z TONIGHT AS THE UPPER LOW 

APPROACHES. WHILE THERE WILL BE LITTLE IF ANY SURFACE REFLECTION OF 

THIS UPPER LOW...IT APPEARS THAT IT WILL BE EFFECTIVE IN DEEPENING 

THE BOUNDARY LAYER WITH TOPS ON FRI AROUND 2500 FT. IFR TO LIFR 

CONDITIONS IN -DZ AND LOW CIGS ARE LIKELY TO CONTINUE THROUGH FRI 

AFTERNOON OR FRI NIGHT. ALBRECHT



KSEA...CONDITIONS HAVE BEEN SLOW TO IMPROVE SINCE THE TERMINAL IS 

WITHIN THE THICKEST FOG LAYER OVER THE PUGET SOUND AREA. EXPECT SOME 

IMPROVEMENT WITH POSSIBLE BREAKS AT TIMES THROUGH THIS EVENING 

BEFORE FOG FILLS BACK IN BY ABOUT 06Z. EXPECT THE FOG LAYER TO LIFT 

INTO A LOW STRATUS WITH DRIZZLE ABOUT 10Z...3/4SM-1SM -DZ BR 

OVC002-004...THAT WILL CONTINUE THROUGH FRI WITH ONLY MODEST 

IMPROVEMENT LATE FRI AFTN. WINDS WILL BE LIGHT THROUGH FRI. ALBRECHT



&&



.MARINE...LIGHT LOW LEVEL ONSHORE FLOW THROUGH SAT. WIDESPREAD FOG 

WITH VISIBILITIES 1/2SM WILL INCREASE OVER THE WATERS THIS 

EVENING...THEN EXPECT DRIZZLE AND FOG ACROSS THE WATERS WITH VIS 

3/4SM-1SM LATE TONIGHT THROUGH FRI NIGHT OR SAT. 



SMALL CRAFT ADVISORY WINDS ARE LIKELY OVER PARTS OF THE COASTAL 

WATERS...ENTRANCES TO THE STRAIT OF JUAN DE FUCA...AND NORTHERN 

INLAND WATERS BEGINNING SUNDAY OR SUNDAY NIGHT AND CONTINUING 

THROUGH MONDAY AS STRONG HIGH PRESSURE DEVELOPS OVER BRITISH 

COLUMBIA AND INCREASES N TO NE FLOW ACROSS THE WATERS. HIGH PRES 

WILL BUILD BACK INTO THE WATERS MON NIGHT AND TUE. ALBRECHT



&&



.SEW WATCHES/WARNINGS/ADVISORIES...

WA...NONE.

PZ...NONE.



&&



$$








FXUS66 KSEW 281524 AAA

AFDSEW



AREA FORECAST DISCUSSION...UPDATED

NATIONAL WEATHER SERVICE SEATTLE WA

724 AM PST THU NOV 28 2013



UPDATED THE AVIATION SEGMENT.



.SYNOPSIS...A WEAK FRONT MAY CLIP THE NORTH COAST FOR LIGHT 

SHOWERS...OTHERWISE EXPECT A DRY THANKSGIVING DAY ACROSS WESTERN 

WASHINGTON. A CHANCE OF RAIN WILL RETURN FOR THE END OF THE WEEK. A 

STRONG COLD FRONT WILL REACH THE AREA SUNDAY FOR RAIN AND HEAVY 

MOUNTAIN SNOW...ALONG WITH WINDY CONDITIONS. THE SNOW LEVEL WILL 

DROP TO NEAR SEA LEVEL BY MONDAY NIGHT. COLD DRY AIR WILL MOVE OVER 

THE REGION FOR MOST OF NEXT WEEK.



&&



.SHORT TERM...THE AIR STAGNATION ADVISORY CONTINUES INTO FRI MORNING 

DUE TO WEAK MIXING AND POOR VENTILATION. 



THE UPPER LEVEL RIDGE WILL WEAKEN/FLATTEN TODAY AS A TROUGH PASSES 

EAST THROUGH B.C. A WEAK FRONT MAY CLIP THE NORTH COAST FOR A FEW 

SPRINKLES...OTHERWISE EXPECT A DRY THANKSGIVING DAY ACROSS THE 

REGION. THERE WILL BE SCATTERED MID AND HIGH CLOUDS FOR PARTLY SUNNY 

SKIES. HIGHS WILL BE NEAR 50 DEGREES. 



THE FLOW ALOFT WILL TURN NORTHWESTERLY FRIDAY AND SATURDAY AS A 

STRONG UPPER LEVEL RIDGE FORMS OFF THE CALIFORNIA COAST. THE MODELS 

SHOW WEAK UPPER LEVEL DISTURBANCES CLIPPING THROUGH WESTERN WA FOR A 

CHANCE OF SHOWERS. 



A STRONG UPPER LEVEL LOW WILL DROP SOUTH FROM THE YUKON TO CENTRAL 

B.C. ON SUNDAY BRINGING WINDY CONDITIONS...RAIN AND MOUNTAIN SNOW TO 

WESTERN WASHINGTON. A 150 KT JET WILL STEER ABUNDANT MOISTURE 

THROUGH THE REGION AND THE MOUNTAINS WILL LIKELY GET HAMMERED WITH 

HEAVY SNOW...6-24 INCHES. SNOW LEVELS WILL INITIALLY START AROUND 

6000 FT...BUT WILL DROP TO 2000 FT TOWARD SUN AFTERNOON AND EVENING. 

TRAVEL OVER THE CASCADES MAY BE DIFFICULT. RAIN WILL ALSO BE HEAVY 

AT TIMES ALONG THE COAST...NORTH INTERIOR AND CASCADE FOOTHILLS - UP 

TO 1 INCH OF RAIN. THE CENTRAL SOUND MAY SEE SOME RAIN SHADOWING 

WITH WESTERLY DOWNSLOPE FLOW OFF THE OLYMPICS. 33



.LONG TERM...A COOL AND UNSTABLE AIR MASS WILL SETTLE OVER WESTERN 

WASHINGTON SUNDAY NIGHT AND MONDAY WITH A 530 DAM UPPER LOW ALOFT. 

THE SNOW LEVELS ARE ONLY A FEW HUNDRED FEET AND THE LOWLANDS COULD 

SEE SCATTERED SNOW SHOWERS...BUT SO FAR ACCUMULATIONS ARE LIGHT. 

HOWEVER WILL NEED TO WATCH THE CONVERGENCE ZONE IN THE INTERIOR 

WHERE THE COLD NLY FRASER RIVER OUTFLOW WILL MEET S/SW MOIST ONSHORE 

FLOW. THE LATEST GFS AND ECMWF ARE A LITTLE SLOWER...SHOWING THE 

LEADING EDGE OF THE ARCTIC FRONT NOW PASSING SOUTH THE INTERIOR MON 

EVENING. PREVIOUS RUNS WERE EARLIER IN THE DAY. SO WILL CONTINUE TO 

WATCH THIS CLOSELY AS WE ARE STILL 5 DAYS AWAY. EXPECT COLD BUT DRY 

WEATHER TUE AND WED WITH LOWS IN THE TEENS TO 20S AND HIGHS ONLY IN 

THE 30S. 33



&&



.HYDROLOGY...FLOODING IS NOT EXPECTED DURING THE NEXT 7 DAYS.



&&



.AVIATION...A WEAK UPPER TROUGH WILL BRUSH WRN WA TODAY THROUGH 

FRIDAY. LIGHT TO MODERATE SW FLOW ALOFT.



THE FOG HAS BECOME MORE WIDESPREAD ACROSS THE AREA THIS MORNING. 

VSBYS AND CIGS WERE GENERALLY AOB 1/2SM AND 200 FT...

RESPECTIVELY...WITH TOPS RUNNING BETWEEN 1000 AND 1100 FT MSL PER 

THE SATELLITE DERIVED CLOUD THICKNESS PRODUCT. AT THIS TIME... 

EXPECTING THE FOG TO DISSIPATE BETWEEN 2000 AND 2200 UTC.    



KSEA...TAF WAS AMENDED TO SHOW LIFR VSBYS/CIGS AS THE PREVAILING 

CONDITIONS. VSBYS SHOULD SLOWLY IMPROVE BETWEEN 1800 AND 2000

UTC...WITH VFR CONDITIONS EXPECTED BY 2200 UTC. ALTHOUGH... 

CONFIDENCE IN THE TIMING WAS NOT VERY HIGH. 



&&



.MARINE...LIGHT SE FLOW OVER THE WATERS...BECOMING SOUTHERLY 

TONIGHT AND FRIDAY IN RESPONSE TO FALLING PRES OVER THE 

CANADIAN COASTAL WATERS AND HIGHER PRES OVER THE OREGON WATERS.



A WEAKENING FRONTAL SYSTEM WILL MOVE ACROSS THE AREA ON SATURDAY... 

FOLLOWED BY A MUCH STRONGER ONE ON SUNDAY. THERE IS THE POTENTIAL 

FOR GALE FORCE WINDS ACROSS PARTS OF THE AREA ON SUNDAY. STRONG 

OFFSHORE OR NE FLOW WILL DEVELOP ON MON IN THE WAKE OF A MODIFIED 

ARCTIC FRONT. IT IS POSSIBLE THAT WINDS COULD REACH GALE FORCE OVER 

THE NORTHERN INLAND WATERS AND PARTS OF THE STRAIT OF JUAN DE FUCA. 

DTM



&&



.SEW WATCHES/WARNINGS/ADVISORIES...

WA...AIR STAGNATION ADVISORY IN EFFECT TIL 10 AM FRI FOR THE PUGET

     SOUND REGION AND SOUTHWEST INTERIOR INTERIOR.



PZ...NONE.



&&



$$



WWW.WEATHER.GOV/SEATTLE



FOR THE GRAPHICAL AFD...VISIT

WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML








FXUS66 KSEW 251112

AFDSEW



AREA FORECAST DISCUSSION

NATIONAL WEATHER SERVICE SEATTLE WA

312 AM PST WED DEC 25 2013



SYNOPSIS...HIGH PRESSURE WILL REMAIN OVER WESTERN WASHINGTON THROUGH 

THURSDAY NIGHT PRODUCING AREAS OF FOG AND LOW CLOUDS. A WEAK WARM 

FRONT MOVING OVER BRITISH COLUMBIA MAY BRUSH THE COAST AND NORTH 

INTERIOR WITH A LITTLE LIGHT RAIN TONIGHT THROUGH THURSDAY NIGHT. A 

WEAK COLD FRONT WILL BRING A SOME RAIN AS IT MOVES ACROSS THE AREA 

ON FRIDAY. AN UPPER LEVEL RIDGE WILL BUILD OVER THE REGION SATURDAY 

THROUGH MONDAY FOR ANOTHER PERIOD OF FOG AND LOW CLOUDS. 



&&



.SHORT TERM...A BROAD UPPER LEVEL RIDGE CENTERED JUST OFFSHORE OVER 

130W THIS MORNING WILL MOVE SLOWLY OVER W WA ON THURSDAY THEN OVER 

ID FRIDAY MORNING. SURFACE HIGH PRESSURE WILL REMAIN OVER THE REGION 

AS WELL. THE RESULTING STABLE AIR MASS WILL KEEP A STRONG LOW LEVEL 

INVERSION OVER W WA THROUGH FRIDAY MORNING...WHICH WILL ALLOW AREAS 

OF FOG AND LOW CLOUDS TO PERSIST THROUGH THE DAY. MAX TEMPS WILL 

ONLY MAKE IT INTO THE LOWER 40S IN AREAS WHERE THE FOG BREAKS 

UP...PERSISTENTLY FOGGY SPOTS WILL PROBABLY BE STUCK IN THE UPPER 

30S. 



A NEW WRINKLE IN THE FORECAST IS A CHANCE OF RAIN FOR THE COAST AND 

FOR THE INTERIOR FROM SEATTLE NORTHWARD TONIGHT AND THURSDAY. WITH 

THE UPPER LEVEL RIDGE OVER THE REGION...THE STORM TRACK HAS BEEN 

DISPLACED N OVER B.C.  HOWEVER WARM ADVECTION HEADED OVER B.C. 

TONIGHT THROUGH THURSDAY NIGHT NOW LOOKS LIKE IT WILL BRUSH THE 

COAST AND N INTERIOR. ANY LIGHT RAIN WILL PROBABLY BE RESTRICTED TO 

THE FAR NORTHERN ZONES...BUT THERE IS STILL A SLIGHT CHANCE AS FAR 

SOUTH AS CENTRAL PUGET SOUND. IF NOTHING ELSE THE WARM ADVECTION 

WILL MAKE SURE SKIES REMAIN MOSTLY CLOUDY THROUGHOUT W WA THE NEXT 

COUPLE OF DAYS.



MODELS REMAIN IN GOOD AGREEMENT IN BRINGING AN UPPER LEVEL SHORTWAVE 

TROUGH AND ASSOCIATED WEAK COLD FRONT ACROSS THE AREA ON FRIDAY. GFS 

SHOWS A FROPA OVER PUGET SOUND AROUND 18Z WHILE THE NAM IS ABOUT 3 

HOURS SLOWER. THIS WILL NOT BE A PARTICULARLY WET FRONT AND 

SHADOWING BY THE OLYMPICS WILL PROBABLY FURTHER REDUCE RAIN 

ACCUMULATIONS OVER CENTRAL PUGET SOUND. THE FRONT SHOULD BE STRONG 

ENOUGH TO MIX OUT THE LOW CLOUDS AND FOG...AT LEAST TEMPORARILY. KAM



.LONG TERM...ANOTHER STRONG UPPER LEVEL RIDGE WILL FORM OFFSHORE 

RIGHT BEHIND THE FRIDAY COLD FRONT...WITH ANOTHER SURFACE HIGH 

SETTLING OVER W WA ON SATURDAY. THE RIDGE WILL WEAKEN BY MONDAY AS 

THE AXIS MOVES E OVER W WA. THIS WILL BE ANOTHER PERIOD WITH A 

STABLE AIR MASS...LOW LEVEL INVERSION...AREAS OF FOG AND LOW CLOUDS 

AND COOL TEMPERATURES. GFS AND ECMWF BOTH SHOW A WEAK UPPER LEVEL 

SHORTWAVE TROUGH CROSSING THE AREA MONDAY OR TUESDAY...BUT IT MAY BE 

EVEN WEAKER THAN FRIDAYS WEAK SYSTEM. THE CURRENT DRY AND FOGGY 

FORECAST LOOKS OK FOR NOW...AND WE WILL HAVE TO SEE HOW THE MONDAY 

SHORTWAVE SHAPES UP. KAM

 

&&



.HYDROLOGY...RIVER FLOODING IS NOT EXPECTED FOR THE NEXT 7 DAYS. 



&&



.AVIATION...WEST NORTHWESTERLY FLOW ALOFT WITH WEAK UPPER LEVEL 

RIDGE OFF THE COAST THROUGH TONIGHT. AIR MASS MOIST AND STABLE.



SATELLITE IMAGERY SHOWS FOG AND LOW CLOUDS FROM JUST SOUTH OF KPAE 

DOWN THE I-5 CORRIDOR TO THE WILLAMETTE VALLEY WITH JUST PATCHY FOG 

ELSEWHERE. SURFACE GRADIENTS ALONG WITH WINDS IN THE LOWER LEVELS 

ARE LIGHT AND WILL REMAIN THAT WAY THROUGHOUT THE DAY. FOG DEPTH 

IMAGERY AT 10Z INDICATING THE LAYER IS MOSTLY BETWEEN 200 AND 300 

METERS DEEP OVER THE LAND AREAS. WITH THE FOG RIGHT ON THE EDGE OF 

KPAE...ELEVATION APPROXIMATELY 600 FEET...THE 200 METER DEPTH 

ESTIMATE LOOKS GOOD. THE LAYER WILL DEEPEN SLIGHTLY UNTIL AFTER 

SUNRISE. VISIBILITIES BELOW A HALF MILE WITH CEILINGS 200 FEET OR 

LESS ARE COMMON IN THE FOGGY AREAS AT 11Z. THESE CONDITIONS WILL 

CONTINUE THROUGH THE MORNING HOURS. BREAKOUT A TOUGH CALL WITH SMALL 

CHANGES IN THE DEPTH OF THE FOG LAYER RESULTING IN SIGNIFICANT 

DIFFERENCES IN THE BREAKOUT TIME. LOCAL APPLICATION FOR KSEA SHOWS 

18Z BREAKOUT FOR 800 FOOT DEEP LAYER VERSUS LITTLE OR NO BREAKOUT 

FOR A 1200 FOOT LAYER. WITH THE LAYER ONLY 200 METERS DEEP AT THIS 

POINT WILL STAY WITH THE IDEA OF TOPS AROUND 1000 FEET LATER THIS 

MORNING WHICH WILL GIVE A EARLY AFTERNOON BREAKOUT. WEAKENING FRONT 

MOVING BY TO THE NORTH THIS EVENING WITH MID LEVEL DECK OVER WESTERN 

WASHINGTON. THIS WILL RESTRICT THE AMOUNT OF GOO THAT DEVELOPS 

TONIGHT.    



KSEA...VISIBILITY 1/4 OF A MILE WITH A 100 FOOT CEILING AT 11Z. NOT 

EXPECTING MUCH IMPROVEMENT UNTIL AROUND 20Z...WITH THE FOG BURNING 

OFF AROUND 22Z. MID LEVEL DECK OVER THE AREA TONIGHT KEEPING FOG TO 

A MINIMUM AT THE TERMINAL. LIGHT WINDS TODAY. FELTON



&&



.MARINE...HIGH PRESSURE WILL REMAIN OVER THE AREA THROUGH THURSDAY 

WITH WEATHER SYSTEMS MOVING BY TO THE NORTH INTO BRITISH COLUMBIA. A 

WEAK FRONT WILL MOVE THROUGH THE WATERS ON FRIDAY. HIGH PRESSURE 

WILL REBUILD BEHIND THE FRONT ON SATURDAY AND REMAIN OVER THE AREA 

ON SUNDAY. FELTON





&&



.SEW WATCHES/WARNINGS/ADVISORIES...

WA...NONE. 

PZ...NONE.



$$



YOU CAN SEE AN ILLUSTRATED VERSION OF THE FORECAST DISCUSSION AT 

WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML
















FXUS66 KSEW 151719

AFDSEW



AREA FORECAST DISCUSSION 

NATIONAL WEATHER SERVICE SEATTLE WA

920 AM PST WED JAN 15 2014



.SYNOPSIS...AN UPPER RIDGE WILL GIVE DRY WEATHER THROUGH FRIDAY 

NIGHT. A WEAK FRONT MAY BRING A LITTLE PRECIPITATION TO THE AREA 

THIS WEEKEND. HIGH PRESSURE WILL STRENGTHEN AGAIN NEXT WEEK.



&&



.SHORT TERM...A STRONG UPPER LEVEL RIDGE CENTERED ALONG ABOUT 130W 

WILL GIVE DRY AND STABLE WEATHER TO WESTERN WASHINGTON THROUGH 

FRIDAY. SURFACE HIGH PRESSURE IS OVER WESTERN WASHINGTON THIS 

MORNING AND WILL GRADUALLY SHIFT EAST INTO SOUTHEASTERN BRITISH 

COLUMBIA AND EASTERN WASHINGTON THURSDAY AND FRIDAY.



SUBSIDENCE INVERSIONS AROUND 5000 FEET AND 2000 FEET ARE 

STRENGTHENING. BY TONIGHT TEMPERATURES AT 2000 FEET WILL RISE TO 

10C-12C WHILE SURFACE TEMPERATURES DROP INTO THE 30S. AS THE SURFACE 

HIGH SHIFTS EASTWARD...SOME WEAK LOW LEVEL OFFSHORE FLOW COMBINED 

WITH THE INCREASED SUBSIDENCE WILL RAISE TEMPERATURES 2000-2500 FEET 

TO 18C-20C PER THE NAM12 BUFR SOUNDINGS. THE STRENGTHENING INVERSION 

IS PUTTING A STRONG LID ON THE BOUNDARY LAYER AND WILL RESULT IN 

VERY POOR VENTILATION AND AIR MOVEMENT ALLOWING MOISTURE AND 

POLLUTANTS TO ACCUMULATE. IT IS STILL MID JANUARY...SO NONE OF THE 

MODELS APPEAR REASONABLE IN THAT THEY ALL MIX DRY AIR ALOFT DOWNWARD 

IN TIME.



THE BIGGEST FORECAST CHALLENGE FOR THE LOWLANDS BELOW ABOUT 1000 FT 

ELEVATION IN THE INTERIOR VALLEYS WILL BE MAXIMUM TEMPERATURES. 

TEMPERATURES ARE LIKELY TO GENERALLY FALL WITH LACK OF MIXING AND 

INSOLATION - AND FOG COVERAGE AND DURATION WILL LIKELY INCREASE BY 

THE DAY THROUGH FRIDAY. BUT HIGHER ELEVATION LOCATIONS LIKE THE LOW 

PLATEAU IN SOUTHWESTERN SNOHOMISH COUNTY...AREAS EAST OF LAKE 

WASHINGTON...AND AREAS AWAY FROM THE IMMEDIATE I-5 CORRIDOR IN THE 

SOUTH INTERIOR ABOVE 500-600 FEET OR SO WILL SEE SUNSHINE DURING THE 

DAY AND MIGHT MANAGE TO GET RATHER WARM - ESPECIALLY FRIDAY. AREAS 

IN THE EAST PUGET SOUND LOWLANDS AND ALONG THE COAST WILL SEE 

TEMPERATURES WELL INTO THE 50S AND MAY SEE LOWER TO MID 60S. AREAS 

BETWEEN 0 AND 500 FEET WILL STRUGGLE TO GET INTO THE LOWER TO MID 

40S. LOW TEMPERATURES WILL ALSO BE A CHALLENGE WITH THE STRONG 

SUBSIDENCE INVERSION ABOVE 1000 FEET OR SO LOCALLY HOLDING 

TEMPERATURES UP AND THE FOG COVERAGE WITH ANY CLEARING WILL IMPACT 

LOWS IN THE LOWER VALLEYS.



WHILE THE PREVIOUS FORECAST LOOKED LIKE IT HAD THE RIGHT IDEA...IT 

APPEARED POSSIBLY A BIT AGGRESSIVE IN MAINTAINING VERY COLD 

TEMPERATURES THROUGH THE DAY IN THE INTERIOR DUE TO THE INVERSION. 

HENCE A MORNING UPDATE WAS MADE NUDGING THE TEMPERATURE FORECASTS 

THROUGH FRIDAY 50 PERCENT TOWARD A MODEL CONSENSUS. IF WE DO CLEAR 

AND GET SOME GOOD RADIATIONAL COOLING THIS EVENING BEFORE FOG AND 

STRATUS FILLS BACK IN...THE PREVIOUS FORECAST COULD WORK OUT. BUT 

CONFIDENCE IN SIGNIFICANT RADIATIONAL COOLING TONIGHT IS LOW ENOUGH 

THAT A CHANGE WAS MADE. NIGHTTIME LOWS WERE ALSO NUDGED UPWARD A FEW 

DEGREES IN THE INTERIOR VALLEYS. ALBRECHT  



.LONG TERM...FROM THE PREVIOUS LONG TERM DISCUSSION...A WEAK WARM 

FRONT MAY CLIP WESTERN WA ON SUNDAY FOR CLOUDY SKIES AND A CHANCE OF 

LIGHT RAIN. AFTER THAT...HIGH PRESSURE WILL ONCE AGAIN BRING A 

PERIOD OF DRY/STABLE WEATHER TO THE AREA MON AND TUE. 33



&&



.HYDROLOGY...RIVER FLOODING IS NOT EXPECTED OVER THE NEXT 7 DAYS. 33



&&



.AVIATION...A STRONG UPPER RIDGE WILL REMAIN OVER THE REGION THRU 

TONIGHT. WEAKENING NW FLOW ALOFT. THE LOW LEVEL FLOW WILL BECOME 

WEAK OFFSHORE THIS AFTERNOON.



THERE WERE AREAS OF CIGS AOB 500 FT AND VSBYS AOB 1SM DUE TO FOG 

OVER MAINLY THE COAST AND THE PUGET SOUND REGION SWD THIS MORNING. 

THE SATELLITE-DERIVED CLOUD THICKNESS PRODUCT INDICATED THAT TOPS 

WERE NEAR 1K FT MSL. EXPECT THE CIGS/FOG TO LIFT OR DISSIPATE THIS 

AFTERNOON...ALTHOUGH THERE WILL PROBABLY BE PATCHES OF IFR 

CIGS/VSBYS THAT WILL PERSIST...ESPECIALLY ALONG THE I-5 CORRIDOR 

FROM KOLM SWD. ANTICIPATE MORE WIDESPREAD DENSE FOG DEVELOPMENT 

TONIGHT.



KSEA...LIFR CIGS ARE EXPECTED TO BREAK OUT ABOUT 2000 UTC. ALSO... 

EXPECT FOG IN THE VICINITY OF THE TERMINAL UNTIL THAT TIME. THE VSBY 

OVER THE TERMINAL ITSELF MAY BRIEFLY LOWER INTO THE 1-SM RANGE THIS 

MORNING. EXPECT THE TERMINAL TO BECOME FOGGED IN AFTER 0600 UTC THU.



&&



.MARINE...

A STAGNANT AIR MASS WILL PREVAIL OVER THE AREA THROUGH AT LEAST FRI 

AND THIS WILL RESULT IN AREAS OF DENSE FOG OVER THE WATERS. THE 

DENSE FOG WILL LIKELY BECOME MORE WIDESPREAD TONIGHT...ESPECIALLY 

OVER THE INTERIOR WATERS. THERE WILL BE LESS FOG OVER THE COASTAL 

WATERS THU NIGHT AND FRI DUE TO INCREASED OFFSHORE FLOW.



BUILDING HIGH PRES OVER SE BRITISH COLUMBIA WILL RESULT IN LIGHT 

NORTHERLY FLOW THIS AFTERNOON. EXPECT INCREASING OFFSHORE OR 

EASTERLY FLOW TONIGHT THROUGH WED DUE TO HIGH PRES OVER SE BRITISH 

COLUMBIA AND GRADUALLY LOWERING PRES OVER THE NE PAC. 



&&



.SEW WATCHES/WARNINGS/ADVISORIES...

WA...AIR STAGNATION ADVISORY ISLAND COUNTY SOUTHWARD IN THE INTERIOR

      LOWLANDS FROM 6 AM TODAY THROUGH 10 AM SATURDAY. 

PZ...SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 4 PM PST

      THIS AFTERNOON FOR WATERS FROM CAPE FLATTERY TO JAMES ISLAND

      10 TO 60 NM-WATERS AND FROM JAMES ISLAND TO POINT GRENVILLE 10

      TO 60 NM.



&&



$$



YOU CAN SEE AN ILLUSTRATED VERSION OF THE FORECAST DISCUSSION AT 

WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML














FXUS66 KSEW 161126

AFDSEW



AREA FORECAST DISCUSSION 

NATIONAL WEATHER SERVICE SEATTLE WA

300 AM PST THU JAN 16 2014



.SYNOPSIS...AN UPPER RIDGE WILL GIVE DRY WEATHER THROUGH FRIDAY 

NIGHT. A WEAK FRONT MAY BRING A LITTLE PRECIPITATION TO THE AREA 

THIS WEEKEND. HIGH PRESSURE WILL STRENGTHEN AGAIN NEXT WEEK.



&&



.SHORT TERM...A STRONG UPPER LEVEL RIDGE IS REMAINS OFFSHORE EARLY 

THIS MORNING...CENTERED ALONG 130W. SURFACE HIGH PRESSURE ALONG THE 

WEST SLOPES OF THE NORTHERN AND CANADIAN ROCKIES IS PRODUCING WEAK 

OFFSHORE LOW LEVEL FLOW. THE WARM AIR ALOFT IS RESULTING IN A STRONG 

INVERSION...AND MOST OF THE WESTERN WASHINGTON INTERIOR LOWLANDS IS 

COVERED IN FOG WITH AREAS OF VISIBILITY HALF MILE OR LESS. 

TEMPERATURES AT 2 AM WERE IN THE MID 30S TO LOWER 40S.



THE UPPER RIDGE WILL SHIFT SLOWLY TOWARD THE COAST TODAY...AND WEAK 

NORTHERLY OFFSHORE FLOW WILL CONTINUE. THE COVERAGE OF FOG SHOULD 

BECOME A BIT MORE WIDESPREAD BEFORE DAYBREAK. IT WILL GRADUALLY 

DECREASE DURING THE DAY...BUT FOG WILL PROBABLY LINGER IN SOME AREAS 

THROUGH THE AFTERNOON. DOWNSLOPE AREAS WITH LITTLE FOG...LIKE THE 

COAST AND WEST SLOPES OF THE CASCADES...SHOULD HAVE HIGHS IN THE 50S 

TODAY WHILE MUCH OF THE INTERIOR LOWLANDS WILL REMAIN IN THE 40S.



THE UPPER RIDGE WILL CONTINUE ITS SLOW PROGRESSION TO THE COAST 

TONIGHT AND FRIDAY. THE OFFSHORE FLOW WILL BE A BIT STRONGER 

FRIDAY...AND DOWNSLOPE AREAS WILL BE EVEN WARMER WITH HIGHS INTO THE 

LOWER 60S. ONCE AGAIN FOG WILL LINGER THROUGH THE AFTERNOON OVER 

PARTS OF THE INTERIOR LOWLANDS WITH HIGHS MAINLY IN THE 40S.



THE MOUNTAINS WILL HAVE MAINLY CLEAR SKIES AND MILD TEMPERATURES 

TODAY AND FRIDAY. THE FREEZING LEVEL WILL BE AROUND 8000 TO 9000 FT 

TODAY AND CLIMB TO ABOVE 10000 FT FRIDAY.



THE NETWORK OF AIR QUALITY SENSORS SHOWS GOOD TO MODERATE AIR 

QUALITY EARLY THIS MORNING. THE STRENGTH OF THE SUBSIDENCE INVERSION 

WILL STRENGTHEN THOUGH...AND VENTILATION WILL REMAIN POOR UNTIL THE 

WEAK FRONT ARRIVES SATURDAY. SO THE AIR STAGNATION ADVISORY REMAINS 

IN EFFECT THROUGH SATURDAY MORNING.



THE UPPER RIDGE WILL WEAKEN AND MOVE INLAND FRIDAY NIGHT...AND THE 

REMAINS OF A DECAYING FRONT WILL REACH THE AREA SATURDAY. IT COULD 

BRING LIGHT PRECIPITATION TO THE AREA...MAINLY THE COAST...BUT EVEN 

THERE THE CHANCE OF MEASURABLE RAIN IS ONLY 30 PERCENT.   MCDONNAL



.LONG TERM...THE UPPER RIDGE WILL REMAIN JUST INLAND ON SUNDAY. THE 

WEAK SYSTEM THAT ARRIVES SATURDAY...OR POSSIBLY ANOTHER WEAK 

SYSTEM...COULD BRING A LITTLE MORE RAIN. THE THREAT IS RATHER LOW... 

AND IF IT DOES RAIN IT WILL PROBABLY BE LIGHT. MONDAY THROUGH 

WEDNESDAY WILL PROBABLY BE DRY...WITH THE UPPER RIDGE REBOUNDING 

OVER THE AREA.   MCDONNAL 



&&



.HYDROLOGY...RIVER FLOODING IS NOT EXPECTED FOR THE NEXT 7 DAYS.



&&



.AVIATION...A STRONG UPPER RIDGE WILL REMAIN OVER THE REGION TODAY 

WITH NORTHWESTERLY FLOW ALOFT. AIR MASS STABLE WITH LOW LEVEL 

MOISTURE. 



SATELLITE IMAGERY SHOWS STRATUS AND FOG MOST OF THE LOWLANDS FROM 

THE EAST ENTRANCE TO THE STRAIT SOUTHWARD. CLEAR SKIES ALONG THE 

COAST AT 11Z BUT STRATUS AND FOG MOVING WESTWARD THROUGH THE LOWER 

CHEHALIS VALLEY WILL GET GET TO THE CENTRAL COAST IN THE NEXT HOUR 

OR TWO. CLOUD TOP AND FOG DEPTH IMAGERY PUTTING THE TOPS IN THE 800 

TO 1300 FOOT RANGE THIS MORNING. OBSERVATIONS BUT THE BASES NEAR 300 

FEET SO TH HIGHER TERMINALS...KSEA AND KPAE ARE IN THE CLOUD DECK. 

LOW LEVEL OFFSHORE FLOW INCREASED OVERNIGHT AND WILL CONTINUE TO 

INCREASE THIS MORNING. BECAUSE OF THIS DO NOT EXPECT THE LAYER TO 

GET MUCH DEEPER THAN IT IS RIGHT NOW. AT THIS DEPTH LOCAL GUIDANCE 

INDICATES A MID AFTERNOON BREAKOUT AND WILL GO FOR THIS SCENARIO IN 

THE TAFS FOR THE CENTRAL SOUND. WITH THE LAYER THINNER OVER THE 

NORTH SOUND AND ALONG THE COAST WILL GO FOR EARLIER BREAKOUT AT KHQM 

AND KBLI. EVEN WITH THE INCREASING OFFSHORE FLOW THIS MORNING LOW 

LEVEL WINDS REMAIN LIGHT ENOUGH TONIGHT FOR THE FOG AND LOW STRATUS 

TO REFORM BEFORE MIDNIGHT.   



KSEA...VISIBILITIES 1/2 SM OR LESS WITH CEILINGS 200 FEET OR LESS 

THIS MORNING. CONDITIONS IMPROVING 20-23Z WITH A MID AFTERNOON 

BREAKOUT. FOG REFORMING AT THE TERMINAL AROUND 06Z FRIDAY. WINDS 

NORTHERLY 4 TO 8 KNOTS THROUGH THIS AFTERNOON. FELTON



&&



.MARINE...LOW LEVEL OFFSHORE FLOW PATTERN TODAY AND FRIDAY WITH HIGH 

PRESSURE CENTERED OVER SOUTHEAST BRITISH COLUMBIA AND LOWER PRESSURE 

OVER THE COASTAL WATERS. OFFSHORE GRADIENTS STRONG ENOUGH TO CREATE 

SMALL CRAFT EASTERLIES AT THE WEST ENTRANCE TO THE STRAIT. THE 

OFFSHORE FLOW WILL EASE ON SATURDAY AS A WEAKENING OCCLUDED FRONT 

DISSIPATES OVER THE COASTAL WATERS. THE OFFSHORE FLOW PATTERN WILL 

RETURN SUNDAY AND MONDAY. FELTON  



&&



.SEW WATCHES/WARNINGS/ADVISORIES...

WA...AIR STAGNATION ADVISORY ISLAND COUNTY SOUTHWARD IN THE          

     INTERIOR LOWLANDS FROM THROUGH 10 AM SATURDAY.

PZ...SMALL CRAFT ADVISORY WEST ENTRANCE TO THE STRAIT.



&&



$$



YOU CAN SEE AN ILLUSTRATED VERSION OF THE FORECAST DISCUSSION AT 

WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML








FXUS66 KSEW 171156

AFDSEW



AREA FORECAST DISCUSSION 

NATIONAL WEATHER SERVICE SEATTLE WA

300 AM PST FRI JAN 17 2014



.SYNOPSIS...AN UPPER RIDGE WILL BRING SUNNY WARM WEATHER TO THE 

COAST AND MOUNTAINS TODAY...WITH LOW CLOUDS AND FOG OVER THE 

INTERIOR LOWLANDS. THE REMAINS OF A WEAKENING FRONT COULD BRING A 

LITTLE RAIN TO THE COAST AND MOUNTAINS THIS WEEKEND...BUT THE 

INTERIOR LOWLANDS SHOULD REMAIN DRY. THE UPPER RIDGE WILL STRENGTHEN 

AGAIN NEXT WEEK FOR MORE DRY WEATHER.



&&



.SHORT TERM...A STRONG UPPER RIDGE IS ALONG 125W EARLY THIS 

MORNING...AS IT PROGRESSES SLOWLY ACROSS THE OFFSHORE WATERS. 

SURFACE HIGH PRESSURE ALONG THE WEST SIDE OF THE NORTHERN AND 

CANADIAN ROCKY MOUNTAINS IS MAINTAINING LOW LEVEL OFFSHORE FLOW 

ACROSS WESTERN WASHINGTON. A STRONG INVERSION CONTINUES...WITH THE 

WARM AIR MASS OF THE RIDGE ALOFT TRAPPING COLDER MOIST AIR AT THE 

SURFACE. SKIES REMAIN MAINLY CLEAR OVER THE COAST AND MOUNTAINS... 

WITH LOW STRATUS AND FOG COVERING THE WESTERN WASHINGTON INTERIOR 

LOWLANDS. TEMPERATURES AT 2 AM WERE IN THE MID 30S TO LOWER 40S.



THE UPPER RIDGE WILL REACH THE COAST THIS AFTERNOON...AND LOW LEVEL 

OFFSHORE FLOW WILL HIT ITS PEAK. THE LAYER OF THE ATMOSPHERE JUST 

ABOVE THE SURFACE WILL BE SEVERAL DEGREES WARMER TODAY THAN IT WAS 

YESTERDAY...SO THE AIR MASS WILL BE EVEN MORE STABLE. THE SUNNY 

AREAS THAT RECEIVE THE BEST DOWNSLOPING...IN PARTICULAR THE OLYMPIC 

COASTLINE...WILL BE EVEN WARMER TODAY. QUILLAYUTE SHOULD REACH THE 

LOWER 60S. BUT INLAND THE STABLE INVERSION SHOULD DOMINATE...AND 

ONCE AGAIN THERE WILL PROBABLY BE LITTLE CLEARING EXCEPT IN THE FAR 

NORTH INTERIOR. TEMPERATURES THERE WILL BE ONLY IN THE 40S. IT WILL 

BE ANOTHER SUNNY WARM DAY IN THE MOUNTAINS.



THE UPPER RIDGE WILL MOVE INLAND TO THE CASCADES TONIGHT AND THEN 

REMAIN MORE OR LESS STATIONARY THROUGH THE WEEKEND. THE REMAINS OF A 

DISSIPATING FRONT WILL REACH THE OFFSHORE WATERS LATE TONIGHT...AND 

IT WILL WEAKEN FURTHER AS IT MOVES TOWARD THE COAST SATURDAY AND 

THEN SLOWLY INLAND ON SUNDAY. THE MOST RECENT MODEL RUNS AGREE 

UNANIMOUSLY THAT THE WESTERN WASHINGTON INTERIOR LOWLANDS WILL NOT 

HAVE MEASURABLE PRECIPITATION THIS WEEKEND...AND I HAVE REMOVED 

MENTION OF RAIN THERE FROM THE FORECAST. SOME MODEL RUNS KEEP SOME 

LIGHT PRECIPITATION OVER THE COAST STARTING LATE SATURDAY...AND IN 

THE OLYMPICS AND PARTS OF THE CASCADES SATURDAY NIGHT AND SUNDAY. 

EVEN THERE THE CHANCE IS AROUND 20 PERCENT...AND ANY PRECIPITATION 

THAT FALLS WILL BE REALLY LIGHT.   MCDONNAL



.LONG TERM...THE UPPER RIDGE WILL REBOUND OVER THE REGION SUNDAY 

NIGHT AND MONDAY. IT WILL KEEP THE AREA DRY AGAIN MONDAY THROUGH 

WEDNESDAY AT LEAST. MODELS HINT AT A WEAK FEATURE MOVING INTO OREGON 

ON THURSDAY...BUT THAT WILL PROBABLY BE ANOTHER DRY DAY FOR OUR 

FORECAST AREA. WEAK OFFSHORE FLOW WILL AGAIN PREVAIL DURING THIS 

PERIOD. THERE WILL AGAIN BE AN INVERSION AND THE FOG AND POTENTIAL 

POOR AIR QUALITY THAT GO ALONG WITH IT.   MCDONNAL 



&&



.HYDROLOGY...RIVER FLOODING IS NOT EXPECTED FOR THE NEXT 7 DAYS.



&&



.AVIATION...UPPER LEVEL RIDGE OVER WESTERN WASHINGTON WITH WEST 

NORTHWESTERLY FLOW ALOFT THROUGH TODAY. AIR MASS STABLE WITH LOW 

LEVEL MOISTURE. 



SATELLITE IMAGERY STILL SHOWS STRATUS AND FOG OVER MOST OF THE 

LOWLANDS WITH THE EXCEPTION OF THE CENTRAL AND NORTHERN COAST. 

STRONG TEMPERATURE INVERSION REMAINING IN PLACE TODAY WITH CONTINUED 

LIGHT FLOW AT THE LOWER LEVELS. CLOUD BASES HAVE LOWERED DOWN TO 200 

TO 400 FEET THIS MORNING. FOG DEPTH AND CLOUD TOP IMAGERY PUT THE 

TOPS BETWEEN 1300 AND 2000 FEET. OFFSHORE GRADIENTS HAVE INCREASED 

EARLY THIS MORNING PUT WINDS IN THE LOWER LEVELS REMAIN FAIRLY 

LIGHT. MODEL CROSS SECTIONS INDICATE THE LIGHT WINDS AT THE LOWER 

LEVELS CONTINUING TODAY. THIS ALONG WITH THE STRONG INVERSION WILL 

KEEP THE STRATUS IN PLACE THROUGH TONIGHT WITH JUST SOME SMALL 

IMPROVEMENTS IN CEILINGS AND VISIBILITIES THIS AFTERNOON AND 

EVENING. THE EXCEPT TO THIS WILL UP NEAR KBLI WHERE THE LAYER IS 

SHALLOWER ALLOWING FOR A AFTERNOON BREAKOUT. 

 

KSEA...CEILINGS 200 FEET OR LESS AND VISIBILITY 1/4 SM INTO THE 

EARLY AFTERNOON HOURS. VISIBILITY SLOWLY IMPROVING UP TO 1 TO 2 SM 

BY 02Z SATURDAY. LIGHT NORTHERLY WINDS THROUGH THIS AFTERNOON. FELTON



&&



.MARINE...LOW LEVEL OFFSHORE FLOW INCREASED OVERNIGHT AND A GALE 

WARNING HAS BEEN ISSUED FOR THE WEST ENTRANCE TO THE STRAIT AND THE 

NORTHERN PORTION OF THE INNER COASTAL WATERS. OFFSHORE GRADIENTS 

EASING THIS AFTERNOON INTO THIS EVENING WITH THE GALE FORCE WINDS 

EASING TO SMALL CRAFT ADVISORY. A WEAKENING FRONT WILL DISSIPATE AS 

IT MOVES ACROSS THE COASTAL WATERS ON SATURDAY WITH THE SURFACE 

GRADIENTS BECOMING LIGHT. THE OFFSHORE FLOW PATTERN WILL REDEVELOP 

ON SUNDAY AND CONTINUE INTO THE MIDDLE OF NEXT WEEK. FELTON



&&



.SEW WATCHES/WARNINGS/ADVISORIES...

WA...AIR STAGNATION ADVISORY REMAINS IN EFFECT UNTIL 10 AM SATURDAY

     FOR THE ADMIRALTY INLET AREA...PUGET SOUND REGION...AND THE

     SOUTHWEST INTERIOR.



PZ...GALE WARNING COASTAL WATERS FROM CAPE FLATTERY TO JAMES ISLAND  

     OUT 10 NM AND THE WEST ENTRANCE TO THE STRAIT OF JUAN DE FUCA.



&&



$$



YOU CAN SEE AN ILLUSTRATED VERSION OF THE FORECAST DISCUSSION AT 

WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML










FXUS66 KSEW 231148

AFDSEW



AREA FORECAST DISCUSSION

NATIONAL WEATHER SERVICE SEATTLE WA

345 AM PST THU JAN 23 2014



.SYNOPSIS...STRONG HIGH PRESSURE ALOFT WILL PREVAIL OVER THE REGION 

THROUGH MONDAY. LOW LEVEL OFFSHORE FLOW WILL STRENGTHEN THIS MORNING 

THROUGH FRIDAY MORNING...THEN WEAKEN ON FRIDAY NIGHT. A FRONT WILL 

REACH THE AREA ON TUESDAY.  



&&



.SHORT TERM...SATELLITE IMAGERY SHOWS HIGH AMPLITUDE RIDGE OFFSHORE 

WITH THE RIDGE AXIS NEAR 130W. LOW CLOUDS OVER PORTIONS OF THE AREA 

AT 3 AM WITH MOSTLY CLEAR SKIES OVER THE NORTHWEST INTERIOR AND THE 

NORTH COAST. IN THE AREAS WHERE THE SKIES CLEARED AREAS OF FOG HAS 

FORMED WITH KUIL AND KBLI REPORTING VISIBILITIES 1/2 MILE OR LESS. 

TEMPERATURES ARE MOSTLY IN THE MID 30S TO LOWER 40S. 



FORECAST PROBLEM FOR THE DAY IS HOW LONG WILL THE LOW CLOUDS AND FOG 

LINGER. BLACK HILLS ARE STICKING OUT ON THE SATELLITE IMAGERY 

PUTTING TOPS SOMEWHERE BELOW 2500 FEET. FOG DEPTH IMAGERY PUTS THE 

TOPS AT 500 METERS OR HIGHER. WILL ESTIMATE THE CLOUD DECK IS ABOUT 

1000 FEET THICK THIS MORNING. SANDPOINT PROFILER SHOWS THE BASE OF 

THE INVERSION STARTING TO SET UP AROUND 600 METERS. WINDS IN THE 

LOWEST LEVELS AND AROUND 500 METERS HAVE GONE EASTERLY WITH A LAYER 

OF NORTHWESTERLY WINDS BETWEEN 200 AND 400 METERS. LOW LEVEL 

OFFSHORE GRADIENTS ARE INCREASING WITH KSEA-KYKM UP TO -5 

MB...KUIL-KBLI -3 MB AND KOTH-KSEA APPROACHING -9 MB. GIVEN THE 

DEPTH OF CLOUD LAYER...THE SATELLITE IMAGERY SHOWING THE LOW CLOUDS 

HAVE NOT SET UP OVER THE ENTIRE LOWLANDS...AND THE INCREASE IN THE 

LOW LEVEL OFFSHORE FLOW WILL GO FOR A BREAKOUT THIS AFTERNOON WITH 

SUNSHINE ACROSS THE AREA. AS WE HAVE SEEN IN THE PAST FEW DAYS WITH 

THE OFFSHORE FLOW THE COAST WILL BE THE WARMEST LOCATION IN THE 

LOWLANDS WITH 50S COMMON. FOR THE REMAINDER OF THE AREA UPPER 40S TO 

MID 50S. IN ADDITION WITH THE INCREASING LOW LEVEL OFFSHORE FLOW 

EXPECT EASTERLY WINDS TO PICK UP IN THE CASCADE FOOTHILLS NEAR GAPS 

IN THE TERRAIN THIS AFTERNOON. 



LITTLE CHANGE IN THE PATTERN TONIGHT WITH THE LOW LEVEL OFFSHORE 

FLOW CONTINUING. MODEL CROSS SECTIONS SHOW LOW LEVEL EASTERLIES 

PEAKING THIS EVENING THEN EASING INTO FRIDAY BUT WITH A DAYS WORTH 

OF EASTERLIES DRYING OUT THE LOWER LEVELS NOT LOOKING FOR MUCH IN 

THE WAY OF LOW CLOUDS AND FOG TO FORM FRIDAY MORNING. WITH THE CLEAR 

SKIES AND THE DRYING LOWER LEVELS LOW TEMPERATURES IN THE COLDER 

LOCATIONS...LIKE THE SOUTHWEST INTERIOR...WILL DROP BELOW FREEZING 

EARLY FRIDAY MORNING. FRIDAY LOOKS TO BE THE WARMEST DAY IN THIS 

SERIES WITH THE WARMER COASTAL LOCATIONS HAVING A SHOT AT BREAKING 

60 DEGREES FRIDAY AFTERNOON. LOWER TO MID 50S WILL BE COMMON OVER 

THE REMAINDER OF THE AREA. GUSTY EASTERLIES WINDS IN THE CASCADE 

FOOTHILLS TONIGHT WILL EASE FRIDAY.



SOME CHANGES IN THE PATTERN START TO SHOW UP LATER FRIDAY INTO 

FRIDAY NIGHT. THE UPPER LEVEL RIDGE AXIS OFFSHORE MOVES INLAND. IN 

ADDITION THE LOW LEVEL OFFSHORE FLOW WEAKENS. MODEL CROSS SECTIONS 

FOR THE INTERIOR LOWLANDS SHOW A TRANSITION TO LIGHT SOUTHERLY WINDS 

FRIDAY NIGHT INTO SATURDAY MORNING IN THE LOWER LEVELS UP TO 850 MB. 

THE INVERSION WILL STILL BE IN PLACE WITH THE BASE OF THE INVERSION 

NEAR 2000 FEET. WITH THE LOW LEVEL EASTERLIES SHUTTING OFF THIS 

CREATES THE POTENTIAL FOR LOW CLOUDS AND FOG TO BECOME MORE 

WIDESPREAD ONCE AGAIN LATER FRIDAY NIGHT INTO SATURDAY MORNING. WITH 

THE INVERSION STILL IN PLACE AND THE LIGHT WINDS AT THE LOWER LEVELS 

ONCE THE FOG AND LOW CLOUDS FORM IT WILL BE TOUGH TO BURN OFF 

SATURDAY AFTERNOON. WILL GO FOR 5 DEGREES OR SO OF COOLING ON 

SATURDAY WITH HIGHS BACK INTO THE 40S FOR THE MOST OF THE LOWLANDS. 



.LONG TERM...EXTENDED MODELS IN GOOD AGREEMENT EARLY ON WITH THE 

HIGH AMPLITUDE UPPER LEVEL RIDGE OVER WESTERN WASHINGTON SUNDAY AND 

MONDAY. LIGHT LOW LEVEL FLOW WILL KEEP PLENTY OF CLOUD COVER AND 

AREAS OF FOG PRESENT. DIFFERENCES IN THE MODEL SOLUTIONS AGAIN SHOW 

UP MONDAY NIGHT INTO TUESDAY. THE GFS WHICH IN PREVIOUS RUNS HAD 

WEAKENED THE APPROACHING FRONT TO THE POINT WHERE LITTLE 

PRECIPITATION WAS LEFT IS NOW A LITTLE STRONGER WITH WHAT IS LEFT OF 

THE FRONT ON TUESDAY BUT STILL SHOWS THE FRONT WEAKENING. THE ECMWF 

IS STILL CONSISTENT IN KEEPING THE FRONT INTACT BUT IS 6 TO 12 HOURS 

SLOWER ON THE 00Z RUN VERSUS THE PREVIOUS RUNS. THE CANADIAN WHICH 

WAS PRETTY CLOSE TO THE ECMWF NOW DOESN'T EVEN BRING THE FRONT 

INLAND AND INSTEAD LEAVES THE UPPER LEVEL RIDGE OVER WESTERN 

WASHINGTON THROUGH TUESDAY BEFORE BRINGING A WARM FRONT IN ON 

WEDNESDAY. GIVEN THE LOW CONFIDENCE WITH THE LACK OF CONSENSUS IN 

THE MODELS BOTH RUN TO RUN AND AMONG THEMSELVES WILL STAY THE 

BROADBRUSH CHANCE POPS FOR TUESDAY AND WEDNESDAY. FELTON 



&&



.HYDROLOGY...RIVER FLOODING IS NOT EXPECTED THE NEXT 7 DAYS.



&&



.AVIATION...A STRONG UPPER LEVEL RIDGE IS OVER THE REGION. A 1036 MB 

HIGH CENTER IS OVER THE SE BRITISH COLUMBIA AND EASTERN WA EARLY 

THIS MORNING. THE AIR MASS IS STABLE WITH AREAS OF LOW LEVEL 

MOISTURE BUT THE LOW LEVEL MOISTURE WILL DRY UP TODAY IN DRYING 

OFFSHORE FLOW WITH LOWERING DEW POINTS. NLY FLOW ALOFT.





KSEA...THE LOW LEVEL AIR WILL DRY TODAY AND IT SHOULD BE CLEAR THIS 

AFTERNOON AND TONIGHT.



&&



.MARINE...OFFSHORE FLOW WILL CONTINUE WITH HIGH PRESSURE OVER B.C. 

AND EASTERN WA. AREAS OF LOW CLOUDS AND PATCHES OF FOG THIS MORNING 

WILL GIVE WAY TO CLEARING FOR MOST AREAS BY AFTERNOON. SMALL CRAFT 

ADVISORY STRENGTH EAST OR NORTHEAST WIND WILL CONTINUE AROUND THE 

WEST ENTRANCE TO THE STRAIT OF JUAN DE FUCA THROUGH FRIDAY MORNING.

THE OFFSHORE FLOW SHOULD EASE FRI NIGHT THROUGH THE WEEKEND. A WEAK 

FRONT WILL APPROACH THE AREA MONDAY. 



&&



.SEW WATCHES/WARNINGS/ADVISORIES...

WA...AIR STAGNATION ADVISORY REMAINS IN EFFECT UNTIL 10 AM PST

     FRIDAY FOR THE ADMIRALTY INLET AREA...PUGET SOUND REGION...

     AND THE SOUTHWEST INTERIOR.



PZ...SMALL CRAFT ADVISORY IN EFFECT FOR THE NORTHERNMOST INNER 

COASTAL WATERS ZONE AND THE WEST ENTRANCE TO THE U.S. STRAIT OF JUAN 

DE FUCA. 



&&



$$



WWW.WEATHER.GOV/SEATTLE



FOR THE GRAPHICAL AFD...VISIT

WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML
















FXUS66 KSEW 021149

AFDSEW



AREA FORECAST DISCUSSION

NATIONAL WEATHER SERVICE SEATTLE WA

350 AM PST SUN FEB 2 2014



.SYNOPSIS...AN UPPER TROUGH WILL MOVE THROUGH THE AREA TONIGHT INTO 

MONDAY. THIS SYSTEM WILL BRING A CHANCE OF SHOWERS WITH SNOW LEVELS 

FALLING TO NEAR SEA LEVEL. MUCH COLDER TEMPERATURES AND DRY WEATHER 

WILL PREVAIL TUESDAY THROUGH FRIDAY. A WEATHER SYSTEM MAY BRING 

RAIN OR SNOW BACK INTO THE AREA FRIDAY NIGHT INTO SATURDAY.



&&



.SHORT TERM...REAL MIXED BAG OF STUFF GOING ON ACROSS WESTERN 

WASHINGTON THIS MORNING. SATELLITE IMAGERY SHOWS CLOUDY SKIES FROM 

ABOUT EVERETT NORTHWARD AND ALONG THE NORTH COAST. SKIES HAVE 

CLEARED OVER THE SOUTHERN PORTION OF THE AREA AND THIS HAS ALLOWED 

FOG TO FORM ALONG THE I-5 CORRIDOR FROM SEATTLE SOUTH THROUGH LEWIS 

COUNTY. UPPER LEVEL LOW OFF THE OREGON COAST SPINNING MID LEVEL 

CLOUD DECK NORTHWARD BUT THE LOW IS MOVING SOUTHEAST SO THE CLOUD 

COVER ASSOCIATED WITH THAT FEATURE WILL NOT REACH THE AREA. WITH THE 

DIFFERENCES IN CLOUD COVER TEMPERATURES IN A WIDE RANGE AT 3 

AM...FROM THE MID 20S TO THE LOWER 40S. 



UPPER LEVEL TROUGH OVER CENTRAL BRITISH COLUMBIA WILL MOVE SOUTH 

TODAY REACHING THE CANADIAN BORDER AROUND 00Z MONDAY. MID LEVEL 

CLOUD DECK OUT AHEAD OF THE TROUGH ALREADY OVER THE NORTHERN PORTION 

OF THE CWA WILL SPREAD SOUTH OVER THE REMAINDER OF THE AREA THIS 

AFTERNOON. OBSERVATIONS FROM AIRCRAFT AT SEA-TAC AIRPORT AND 

SANDPOINT PROFILER INDICATE NO INVERSION IS PRESENT. FOG LAYER 

SHALLOW WITH TOPS AT OR BELOW 1000 FEET. OBSERVATIONS ALSO SHOW 

LIGHT WINDS AT THE LOWER LEVELS. TOUGH CALL ON WHEN THE FOG WILL 

BURN OFF TODAY. BECAUSE OF THE FOG DEPTH WILL ONLY MENTION IT IN THE 

MORNING PORTION OF THE FORECAST. AS THE TROUGH GETS CLOSER TO THE 

AREA THIS AFTERNOON A CHANCE OF SHOWERS WILL DEVELOP. FIRST IN THE 

NORTH AND THEN SPREADING OVER THE ENTIRE AREA DURING THE AFTERNOON. 

MODELS ARE CONTINUING WITH THE IDEA THAT THE TROUGH IS FAIRLY DRY. 

WILL STAY WITH THE POPS IN THE 20-30 PERCENT RANGE. HIGH 

TEMPERATURES TODAY WILL ONCE AGAIN RANGE FROM THE UPPER 30S TO THE 

MID 40S.



UPPER LEVEL TROUGH MOVING THROUGH THE AREA TONIGHT WITH THE BEST 

CHANCE OF SHOWERS OVERNIGHT INTO THE EARLY MORNING HOURS ON MONDAY. 

TEMPERATURES ALOFT COOLING WITH THE SNOW LEVEL LOWERING TO NEAR SEA 

LEVEL BY MONDAY MORNING...1000-850 MB THICKNESS VALUES WELL BELOW 

1300 METERS...SO THERE IS A CHANCE OF SNOW SHOWERS ESPECIALLY AFTER 

MIDNIGHT BUT THIS IS A LOW QPF SITUATION. EVEN IF ANY SHOWERS TO 

DEVELOP THEY WILL NOT AMOUNT TO MUCH. TEMPERATURES WILL COOL DOWN 

INTO THE MID 20S TO MID 30S MY MONDAY MORNING.



TROUGH SLOWING MAKING ITS WAY OUT OF THE AREA ON MONDAY WITH 

CLEARING FROM THE NORTH AS THE DAY WEARS ON. WITH THE TROUGH IN THE 

AREA MONDAY MORNING THERE STILL IS A CHANCE OF A COUPLE SNOW SHOWERS 

BUT AS WAS THE CASE FOR SUNDAY NIGHT IF THERE IS ANY SHOWER ACTIVITY 

PRECIPITATION AMOUNTS WILL BE VERY LIGHT. COOLER AIR MOVING INTO THE 

AREA ALOFT WITH THE 850 MB TEMPERATURES DOWN TO NEAR -10C BY 00Z 

TUESDAY. COOLER AIR ALSO MOVING INTO THE AREA AT THE SURFACE WITH 

THE KBLI-CWYL DOWN TO AROUND -12 MB BY 18Z MONDAY. EXPECT WINDY 

CONDITIONS TO DEVELOP UP IN THE SAN JUANS AND WHATCOM COUNTY WITH 

NORTHEASTERLY FRASER RIVER OUTFLOW. HIGH TEMPERATURES ON MONDAY WILL 

ONLY GET INTO THE LOWER 40S IN THE WARMER LOCATIONS. 



DRY...COLDER AIR CONTINUING TO POUR INTO THE REGION AT ALL LEVELS 

MONDAY NIGHT INTO TUESDAY. 850 MB TEMPERATURES DOWN TO AS LOW AS 

-14C BY 00Z WEDNESDAY. FRASER OUTFLOW WINDS CONTINUING OVER THE 

NORTHERN PORTION OF THE AREA WITH THE KBLI-CWYL GRADIENT REMAINING 

AROUND -12 MB. LOW TEMPERATURES WITH THE CLEARING SKIES WILL FALL 

INTO THE TEENS IN MANY PLACES MONDAY NIGHT WITH HIGHS ONLY 

RECOVERING INTO THE 30S ON TUESDAY. 



.LONG TERM...EXTENDED MODELS IN GOOD AGREEMENT WEDNESDAY AND 

THURSDAY WITH THE UNSEASONABLY COLD AIR MASS REMAINING OVER WESTERN 

WASHINGTON. BOTH THE GFS AND THE ECMWF HAVE AN UPPER LEVEL TROUGH ON 

WEDNESDAY RETROGRADING AND TURNING INTO A CLOSED LOW ON THURSDAY. 

ANY MOISTURE ASSOCIATED WITH THE TROUGH AND CLOSED LOW WELL TO THE 

SOUTH OF THE AREA. WITH THE CLEAR SKIES AND COLD AIR MASS IN PLACE 

LOWS IN THE TEENS WILL BE COMMON TUESDAY NIGHT AND WEDNESDAY NIGHT 

WITH HIGHS ONLY RECOVERING BACK TO THE LOWER TO MID 30S WEDNESDAY 

AND THURSDAY. SOME CHANGES IN THE PATTERN START TO SHOW UP ON FRIDAY 

AS A SYSTEM WELL OFFSHORE STARTS TO MAKE ITS WAY TOWARD WESTERN 

WASHINGTON WHILE THE UPPER LEVEL LOW KICKS OUT TO THE EAST. BOTH THE 

GFS AND THE ECMWF ARE A LITTLE SLOWER WITH THE APPROACH OF THE FRONT 

WITH THE 00Z RUNS HOLDING OFF THE PRECIPITATION UNTIL SATURDAY. BOTH 

THE GFS AND THE ECMWF ON THE 00Z RUN ALSO INDICATING THE INCOMING 

SYSTEM BECOMING MORE NEGATIVELY TILTED BY SATURDAY. THIS SOLUTION 

KEEPS THE LOW LEVEL FLOW OVER WESTERN WASHINGTON OFFSHORE AS THE 

SYSTEM MOVES INTO THE AREA ON SATURDAY CREATING AN OVERRUNNING 

SCENARIO WHICH COULD ALLOW THE COLD AIR TO STAY IN PLACE AT LEAST 

INITIALLY AS THE PRECIPITATION STARTS. WAY TOO EARLY FOR ANY KIND OF 

SPECIFICS BUT THERE IS A POSSIBILITY OF SNOW ON SATURDAY ACROSS THE 

LOWLANDS BEFORE THE PRECIPITATION TRANSITIONS TO RAIN. WILL WAIT FOR 

ANOTHER RUN OR TWO BEFORE TAKING THE CHANCE POPS OUT OF FRIDAY NIGHT 

FORECAST. CURRENT FORECAST HAS CHANCE OF RAIN OR SNOW ON SATURDAY 

AND AT THIS POINT THAT LOOKS GOOD. FELTON



&&



.AVIATION...WESTERLY FLOW ALOFT OVER WESTERN WASHINGTON EARLY THIS 

MORNING WILL CONTINUE TODAY...THEN VEER TO NORTHWEST TONIGHT AS AN 

UPPER TROUGH MOVES THROUGH THE FORECAST AREA. NORTHERLY OFFSHORE 

FLOW WILL CONTINUE AT THE SURFACE. THE AIR MASS WILL REMAIN 

GENERALLY MOIST BELOW 8000 FT AND DRY ABOVE. IN ADDITION THERE ARE 

AREAS OF LOW LEVEL MOISTURE RESULTING IN FOG AND STRATUS THIS 

MORNING. 



SKIES CLEARED SOMEWHAT LATE SATURDAY EVENING...WHICH ALLOWED AREAS 

OF FOG AND STRATUS TO DEVELOP QUICKLY. AS A RESULT THERE ARE AREAS 

OF VISIBILITY AND CEILING AT OR BELOW 1/2SM FG VV002 MAINLY IN THE 

SOUTH PUGET SOUND REGION...SOUTHWEST INTERIOR...AND LOWER CHEHALIS 

VALLEY. THIS WILL PROBABLY BECOME A BIT MORE WIDESPREAD DURING THE 

NEXT FEW HOURS BEFORE IMPROVING TO VFR MIDDAY TODAY. IN ADDITION 

THERE IS UPSLOPE STRATUS ALONG THE NORTH SIDE OF THE OLYMPIC 

PENINSULA FOR LOCAL MVFR CEILINGS...AND THAT WILL LIKELY CONTINUE 

THROUGH TONIGHT. 



OTHERWISE CONDITIONS SHOULD BE MAINLY VFR...BUT THERE IS A LAYER OF 

CLOUDS WITH BASES AROUND 7000 FT OVER THE NORTHWEST INTERIOR AND 

EXTENDING INTO BRITISH COLUMBIA...AND IT WILL LIKELY PUSH SOUTHWARD 

OVER THE AREA LATE TODAY AND TONIGHT AS THE UPPER TROUGH MOVES 

THROUGH. 



KSEA...NORTHERLY WIND 6 KT OR LESS RISING TO 4-10 THIS AFTERNOON. 

LIFR CONDITIONS IN FOG WILL LIKELY CONTINUE THROUGH AROUND 21Z... 

BUT THAT IS SOMETHING OF A GUESS.   MCDONNAL



&&



.MARINE...HIGH PRESSURE  OVER SOUTHEAST BRITISH COLUMBIA AND EASTERN 

WASHINGTON WILL PRODUCE NORTHERLY OFFSHORE FLOW TODAY. THE HIGH OVER 

BRITISH COLUMBIA WILL STRENGTHEN TONIGHT RESULTING IN STRONGER 

NORTHEASTERLY FRASER OUTFLOW WINDS THROUGH THE MIDDLE OF THE 

WEEK...ESPECIALLY IN THE NORTHERN INLAND WATERS. 



SMALL CRAFT ADVISORIES HAVE BEEN ISSUED WITH THE MORNING FORECAST 

PACKAGE FOR TONIGHT AND MONDAY FOR MOST MARINE ZONES. NOTE THAT THE 

WINDS WILL LIKELY CONTINUE THROUGH AT LEAST TUESDAY THOUGH...AND IN 

FACT CURRENT MODELS SUGGEST THEY WILL HIT THEIR PEAK STRENGTH MONDAY 

NIGHT. ACCORDINGLY A GALE WATCH HAS BEEN ISSUED FOR THE NORTHERN 

INLAND WATERS FOR MONDAY NIGHT THROUGH TUESDAY MORNING.  



NORTHEAST FLOW IS LIKELY TO CONTINUE ACROSS MOST OF THE WATERS 

THROUGH WEDNESDAY NIGHT OR THURSDAY.   MCDONNAL



&&



.SEW WATCHES/WARNINGS/ADVISORIES...

WA...NONE. 

PZ...SMALL CRAFT ADVISORY COASTAL WATERS ZONES 150...153...173.

     SMALL CRAFT ADVISORY WEST ENTRANCE STRAIT...CENTRAL STRAIT...

      EAST ENTRANCE STRAIT...NORTHERN INLAND WATERS...PUGET SOUND

      AND HOOD CANAL.

     GALE WATCH NORTHERN INLAND WATERS FOR MONDAY NIGHT THROUGH 

      TUESDAY MORNING.



&&



$$
















FXUS66 KSEW 060546

AFDSEW



AREA FORECAST DISCUSSION 

NATIONAL WEATHER SERVICE SEATTLE WA

945 PM PST WED MAR 5 2014



.SYNOPSIS...A WEAKENING LOW CENTER WILL REACH CENTRAL VANCOUVER 

ISLAND ON THURSDAY MORNING. A TRAILING COLD FRONT WILL CROSS WESTERN 

WASHINGTON ON THURSDAY AFTERNOON. BREEZY AND SHOWERY WEATHER IS 

EXPECTED THROUGH THURSDAY EVENING. AN UPPER RIDGE WILL PROVIDE DRIER 

WEATHER AND SOME SUN BREAKS ON FRIDAY...BUT ANOTHER FRONT WILL BRING 

MORE RAIN THIS WEEKEND AND EARLY NEXT WEEK.



&&



.SHORT TERM...A SURFACE LOW WILL GRADUALLY FILL AS IT TRACKS NE 

TOWARD CENTRAL VANCOUVER ISLAND OVERNIGHT AND THU MRNG. IN ADVANCE 

OF THE LOW...A WARM FRONT QUICKLY SPREAD N THROUGH WRN WA EARLIER 

THIS EVNG...WITH A FEW HOURS OF WIDESPREAD MODERATE TO HEAVY RAIN 

RAIN DURING THE EVENING COMMUTE. THE HEAVIER STRATIFORM PRECIP HAS 

NOW EXITED THE FCST AREA...BUT VIGOROUS SHOWER ACTIVITY HAS 

BLOSSOMED OFF THE COAST THIS EVNG. CLOUD TOP TEMPS ON IR IMAGERY IN 

CONVECTIVE ELEMENTS SUGGESTS AN ISOLATED STRIKE OF LIGHTNING IS 

POSSIBLE FOR THE NEXT FEW HOURS. SW 850 MB FLOW OF 50-60 KT HAS 

ALREADY SHOWN SIGNS OF ORGANIZING CONVECTION INTO NARROW LINES OVER 

SW WA...LIKELY CONTAINING SMALL AREAS OF INTENSE RAINFALL. THE 

STRONG LOW-LEVEL FLOW WILL ALSO FOCUS RAIN INTO MOUNTAIN HEADWATERS 

TONIGHT AND THU...SO RIVER FLOODING WILL CONTINUE TO BE A CONCERN. 

WRN WA WILL REMAIN IN THE WARM SECTOR OF THE SFC LOW UNTIL A 

TRAILING COLD FRONT PUSHES THROUGH WRN WA ON THU AFTN. THIS WILL 

TURN THE LOW-LEVEL FLOW TO A MORE WESTERLY COMPONENT AND BRING AN 

INCREASE IN ONSHORE WINDS THROUGH THE STRAIT AND INTO THE PUGET 

SOUND REGION FROM SEATTLE ON SOUTH. SOMEWHAT COOLER AIR MASS WILL 

FOLLOW...WITH THE FREEZING LEVEL FALLING DOWN TO NEAR 4500 FEET BY 

THU EVNG...WITH THE SNOW LEVEL DROPPING BACK BELOW STEVENS PASS.  

HANER



REMAINDER OF SHORT TERM SECTION FROM PREVIOUS DISCUSSION...

HIGH PRESSURE WILL MIGRATE OVER THE PAC NW FRIDAY AND FRIDAY NIGHT. 

THE RIDGE IS DIRTY WITH MOISTURE MOVING OVER THE TOP POSSIBLY 

PRODUCING SPOTTY LIGHT RAIN. THERE MAY ALSO BE SOME SUNSHINE SO 

CLOUD COVER WAS DECREASED IN THE GRIDS. THE NEXT MOIST FRONTAL 

SYSTEM ARRIVES SATURDAY. MODELS ARE SOMEWHAT FASTER WITH RAIN OVER 

THE WEEKEND INSTEAD OF ANY BREAK.   MERCER



.LONG TERM...FROM PREVIOUS DISCUSSION...WEAK HIGH PRESSURE OVER THE 

INTERIOR PAC NW SUNDAY MOVES E ON MONDAY. THIS OPENS THE DOOR TO 

STRONG WESTERLY FLOW AND A SERIES OF FRONTS MAINTAINING UNSETTLE 

WEATHER. THE ECMWF SHOWS THE WEEKEND SYSTEM TO BE STRONG WITH SLOW 

MOVEMENT AND TONS OF MOISTURE BEING ENTRAINED. THE GFS IS A SOMEWHAT 

WEAKER BUT STRONG REGARDLESS. LOW PRESSURE MOVES E OF TUESDAY WITH 

MAYBE A CHANGE TO SHOWERS BUT TIMING IS HIGHLY UNCERTAIN.  MERCER 



&&



.HYDROLOGY...DURATION OF THE HEAVIER AND MORE WIDESPREAD RAIN BAND 

EARLIER THIS EVENING WAS RELATIVELY SHORT...LASTING ABOUT 3 HOURS. 

VIGOROUS SHOWER ACTIVITY NOW MOVING ONTO THE COAST...WITH SW 850 MB 

WINDS OF 50-60 KT SERVING TO FOCUS PRECIP FOR THE REST OF TONIGHT ON 

MOUNTAINOUS TERRAIN. STILL...THE SHORTER DURATION OF THE WARM 

FRONTAL PRECIP EARLIER TONIGHT WAS WELCOME. 



RFC FORECAST SHOWS SNOQUALMIE AT CARNATION GOING OVER FLOOD STAGE 

TONIGHT...BUT UPSTREAM GAGE AT THE FALLS SHOWS DECLINING FLOWS...AND 

THE PEAK FLOW AT THE FALLS AROUND 16300 CFS DOES NOT BOLSTER 

CONFIDENCE IN ACHIEVING FLOOD STAGE AT CARNATION. APPEARS THAT RIVER 

LEVEL AT CARNATION IS LEVELING OFF NOW...SO NO FLOOD WARNING THERE 

BASED ON LATEST TRENDS. 



MORE RAIN OCCURRED THIS AFTN OVER THE UPPER COWLITZ BASIN THAN 

FORECAST. RFC FORECAST BUMPED UP THE TIMING ON REACHING FLOOD STAGE 

AT RANDLE...WITH THE FORECAST TO REACH FLOOD STAGE AROUND MID-DAY 

THU. RIVER TRACKING WELL WITH THE MORE BULLISH UPDATED FORECAST. MAY 

NEED TO ISSUE A FLOOD WARNING OVERNIGHT FOR THE COWLITZ AT RANDLE. 



OTHERWISE...WARNING CONTINUES ON THE SKOKOMISH...WITH ANOTHER RISE 

EXPECTED ON THU. ALSO WATCHING THE SATSOP...CHEHALIS AND PUYALLUP 

RIVER BASINS CLOSELY.   HANER





&&



.AVIATION...A FAST MOVING WARM FRONT IS MOVING ACROSS W WA THIS 

EVENING AND BASED ON RADAR...EXTENDED FROM THE N COAST ACROSS PUGET 

SOUND AT 04Z. PRECIPITATION HAS BEEN BREAKING UP OVER THE AREA BUT 

IS STILL WIDESPREAD. ECHOES OVER THE SW PART ARE SHOWING THE 

STREAKINESS THAT INDICATES STRONG LOW LEVEL SW WINDS.



AN UPPER LEVEL TROUGH AND SURFACE LOW ALONG 130W AT 04Z WILL MOVE 

OVER THE COAST AND CENTRAL VANCOUVER ISLAND RESPECTIVELY BY 18Z. THE 

AIR MASS WILL REMAIN MOIST WITH INTERMITTENT RAIN. CONDITIONS WILL 

GRADUALLY LOWER TO PREDOMINATELY MVFR CIGS BKN-OVC010-030 WITH LOCAL 

IFR CIGS POSSIBLE. VISIBILITY WILL LOWER TO MVFR AROUND RAIN. 

CONDITIONS SHOULD IMPROVE TO VFR AFTER 18Z AS THE TROUGH MOVES E.



KSEA...THE WARM FRONT IS PAST KSEA SO RAIN WILL BE MORE INTERMITTENT 

THE REST OF TONIGHT AND THURSDAY MORNING AS THE UPPER LEVEL TROUGH 

APPROACHES THE AREA. CIGS SHOULD LOWER BY 08Z SO THAT THEY ARE 

PREDOMINANTLY MVFR PROBABLY BKN020-030. GUSTY S-SW SURFACE WINDS 

15G25KT ARE STILL EXPECTED 08Z-18Z...AND LOW LEVEL WINDS FL025-FL050 

SHOULD BE IN THE 40-50KT RANGE. KAM



&&



.MARINE...A WARM FRONT IS MOVING QUICKLY ACROSS W WA THIS EVENING 

AND BASED ON RADAR...EXTENDED FROM THE N COAST ACROSS PUGET SOUND AT 

04Z. SURFACE WINDS OVER THE INTERIOR WILL SHIFT TO S AND INCREASE 

BEHIND THE WARM FRONT. THE MAIN SURFACE LOW WAS STILL OUT AROUND 

46.5N/130W AT 04Z AT AROUND 983 MB. MODELS FILL IT TO AROUND 994 MB 

BY 18Z THURSDAY WHILE MOVING IT TO THE CENTRAL B.C. COAST. MODELS 

SHOW A TROUGH AXIS ROTATING AROUND THE LOW DURING THIS PERIOD WHICH 

SHOULD SHIFT THE WINDS FROM SOUTHERLY TO W-SW AS IT MOVES ACROSS THE 

AREA THURSDAY MORNING THROUGH EARLY THURSDAY AFTERNOON. WINDS SHOULD 

BE GRADUALLY EASING THURSDAY AFTERNOON...EXCEPT FOR W FLOW THROUGH 

THE STRAIT WHICH WILL BE INCREASING TO AROUND SCA LEVELS FOR A SHORT 

PERIOD.



A SURFACE RIDGE WILL GRADUALLY BUILD INLAND OVER W WA THURSDAY NIGHT 

AND FRIDAY...AND WILL LAST THROUGH FRIDAY NIGHT.



S FLOW WILL GRADUALLY INCREASE SATURDAY AS ANOTHER FRONTAL SYSTEM 

APPROACHES THE REGION FROM OFFSHORE. THE COLD FRONT SHOULD CROSS THE 

AREA LATE SATURDAY NIGHT THROUGH EARLY SUNDAY MORNING. 00Z NAM SHOWS 

SCA WINDS OVER THE COASTAL WATERS...BUT WILL AWAIT THE 00Z WRF-GFS 

TO SEE IF IT STILL SUPPORTS BORDERLINE GALES. ANOTHER SURFACE RIDGE 

WILL BUILD INLAND BEHIND IT ON SUNDAY. KAM 



&&



WA...WIND ADVISORY FOR THE COAST.

     FLOOD WATCHES AND/OR WARNINGS FOR PARTS OF THE FORECAST AREA. 

PZ...GALE WARNING COAST.

     SMALL CRAFT ADVISORY ALL OTHER WATERS.



&&



$$



YOU CAN SEE AN ILLUSTRATED VERSION OF THE FORECAST DISCUSSION AT 

WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML






















FXUS66 KSEW 031018

AFDSEW



AREA FORECAST DISCUSSION 

NATIONAL WEATHER SERVICE SEATTLE WA

318 AM PDT TUE JUN 3 2014



.SYNOPSIS...HIGH PRESSURE OVER THE NORTHEAST PACIFIC WILL MAINTAIN 

LOW LEVEL ONSHORE FLOW THIS WEEK. THIS PATTERN WILL PRODUCE DRY AND 

MILD WEATHER ACROSS THE REGION. AN UPPER LEVEL TROUGH MAY TRIGGER A 

FEW SHOWERS LATE IN THE WEEKEND AS IT CUTS THROUGH THE AREA. 



&&



.SHORT TERM...HIGH PRES OVER THE NE PAC WILL MAINTAIN ONSHORE FLOW 

ACROSS WESTERN WA OVER THE NEXT SEVERAL DAYS. PRESSURE GRADIENTS ARE 

A BIT STRONGER THIS MORNING COMPARED TO YESTERDAY AND THE STRATUS 

COVERAGE IS MORE EXTENSIVE. MOST OF THE LOWLANDS WILL BE COVERED BY 

THE CLOUDS BY SUNRISE. THE STRATUS WILL BE THICKER TODAY WHICH WILL 

ALSO LEAD TO A LATER BREAK OUT. THE COAST WILL LIKELY REMAIN IN THE 

CLOUDS ALL DAY. HIGHS WILL RANGE FROM THE 60S ALONG THE COAST TO 

UPPER 60S OR LOW 70S INTERIOR. 



ONSHORE GRADIENTS ARE EVEN STRONGER ON WEDNESDAY AND THERE IS A 

CHANCE THAT THE CENTRAL SOUND WILL STAY CLOUDY THROUGHOUT MUCH OF 

THE AFTERNOON. MODELS ARE SHOWING LOW LEVEL CONVERGENCE IN THE 

CENTRAL SOUND WHICH WILL LIFT AND DEEPEN THE MARINE LAYER. HOWEVER 

THE NORTHWEST INTERIOR...STRAIT AND SW INTERIOR MAY SEE SOME 

SUNBREAKS. 



EXPECT MORE SUNSHINE ON THURSDAY AS THE SURFACE FLOW PATTERN 

SWITCHES TO NORTHERLY. MODELS SHOW AN INVERTED SURFACE TROUGH 

FORMING ALONG THE WEST COAST WITH A WEAKER PRES GRADIENT ACROSS 

WESTERN WA. THE UPSHOT WILL BE LESS CLOUDS OVERALL DURING THE 

MORNING HOURS...WITH MOSTLY SUNNY SKIES RETURNING. THE PATTERN 

REPEATS ON FRIDAY. 33



.LONG TERM...ONSHORE FLOW WILL CONTINUE THROUGH THIS WEEKEND AND 

INTO EARLY NEXT WEEK. EXPECT THE USUAL TREND OF LATE NIGHT AND 

MORNING CLOUDS WITH AFTERNOON SUNBREAKS. AN UPPER LEVEL TROUGH WILL 

CUT THROUGH SOUTHERN B.C. ON SUNDAY WHICH MAY TRIGGER A FEW SHOWERS 

OVER THE CASCADES. OTHERWISE THE REST OF THE AREA WILL CONTINUE TO 

SEE DRY AND MILD WEATHER. 33



&&



.AVIATION...VERY WEAK UPPER TROUGH OVER THE AREA WILL MOVE INTO 

EASTERN WASHINGTON LATE THIS MORNING INTO THIS AFTERNOON. LIGHT 

NORTHWESTERLY FLOW ALOFT. ONSHORE FLOW CONTINUING AT THE LOWER 

LEVELS. 



SATELLITE IMAGERY AT 0930Z/230 AM SHOWS STRATUS ALONG THE 

COAST...OVER THE SOUTHWEST INTERIOR...HOOD CANAL AND SOUTH PUGET 

SOUND. EXPECT THE STRATUS TO FILL IN OVER THE REMAINDER OF THE 

INTERIOR FROM SNOHOMISH COUNTY SOUTHWARD IN THE NEXT COUPLE OF 

HOURS. GOES CLOUD THICKNESS IMAGERY INDICATING THE LAYER IS 900-1200 

FEET THICK. WITH THE BASES IN THE 1000-1800 FOOT MSL RANGE THIS PUTS 

THE TOPS IN THE 2000-3000 FOOT RANGE. ONSHORE GRADIENTS HAVE 

WEAKENED OVERNIGHT AND WITH THE STRATUS NOT REACHING THE NORTHWEST 

INTERIOR THIS WILL ALLOW THE STRONG EARLY JUNE SUN TO START BURNING 

OFF THE MARINE LAYER THIS MORNING. ANOTHER MIDDAY/EARLY AFTERNOON 

BREAKOUT IS EXPECTED FOR THE INTERIOR WITH THE STRATUS HANGING TOUGH 

RIGHT ALONG THE COAST. 



KSEA...STRATUS...RIGHT ACROSS THE WATER AT KTIW AT 10Z...WILL ARRIVE 

AT THE TERMINAL IN THE NEXT HOUR OR TWO WITH CEILINGS NEAR 1000 

FEET. SLOW IMPROVEMENT LATE MORNING WITH THE CLOUDS SCATTERING OUT 

EARLY AFTERNOON. SOUTHERLY WINDS 4 TO 8 KNOTS THROUGH EARLY 

AFTERNOON BECOMING WEST SOUTHWESTERLY MID TO LATE AFTERNOON. FELTON



&&



.MARINE...HIGH PRES OVER THE NORTHEAST PACIFIC AND LOWER PRES EAST 

OF THE CASCADES WILL MAINTAIN ONSHORE FLOW OF VARYING STRENGTH INTO 

THE WEEKEND. 



00Z MODEL RUNS HAVE BACKED OFF THE STRENGTH OF THE GRADIENT THROUGH 

THE STRAIT TONIGHT. WILL GO WITH A PERSISTENCE FORECAST OF 20 TO 30 

KNOTS AGAIN THIS EVENING.  



SMALL CRAFT ADVISORY WINDS CONTINUING OVER THE OUTER COASTAL WATERS 

WITH AT LEAST SMALL CRAFT ADVISORY WINDS IN THE CENTRAL AND EASTERN 

STRAIT IN THE EVENING AND EARLY MORNING HOURS INTO THE WEEKEND. 

FELTON



&&



.SEW WATCHES/WARNINGS/ADVISORIES...

WA...NONE.

PZ...SMALL CRAFT ADVISORIES ARE IN EFFECT FOR THE CENTRAL/EASTERN

     STRAIT OF JUAN DE FUCA AND THE COASTAL WATERS FROM CAPE

     FLATTERY TO CAPE SHOALWATER FROM 10 NM OUT TO 60 NM.

&&



$$



WWW.WEATHER.GOV/SEATTLE



FOR THE GRAPHICAL AFD...VISIT

WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML


























FXUS66 KSEW 071015

AFDSEW



AREA FORECAST DISCUSSION

NATIONAL WEATHER SERVICE SEATTLE WA

315 AM PDT MON JUL 7 2014



.SYNOPSIS...HIGH PRESSURE ALOFT WILL PREVAIL OVER THE REGION

THROUGH TUESDAY. THE HIGH WILL MOVE EAST TUESDAY NIGHT...ALLOWING

THE TAIL END OF A LOW PRESSURE SYSTEM TO MOVE ACROSS THE AREA ON

WEDNESDAY. THE MAIN IMPACT THIS WILL HAVE ON OUR WEATHER WILL BE

TO INITIATE A MARINE PUSH...RESULTING IN COOLER TEMPERATURES ON

WEDNESDAY.



&&



.SHORT TERM...

THERE WERE AREAS OF LOW CLOUDS AND FOG OVER THE CWA EARLY THIS

MORNING. THE CLOUD BASES WERE QUITE LOW OR LESS THAN 500 FT AGL.

PER THE EXPERIMENTAL SATELLITE-DERIVED FOG DEPTH ESTIMATE...THE

CLOUD TOPS WERE NEAR 1K FT. THUS ANTICIPATE A FAIRLY QUICK BURN-

OFF...WITH SUNNY SKIES PREVAILING THIS AFTERNOON.



AN UPPER RIDGE WILL PREVAIL OVER THE REGION THROUGH TUE. THE

RIDGE WILL SHIFT EAST OF THE AREA TUE NIGHT...ALLOWING THE TAIL

END OF AN UPPER TROF TO MOVE OVER THE AREA ON WED. THE MAIN

IMPACT THIS WILL HAVE ON OUR WEATHER WILL BE TO INDUCE A MARINE

PUSH...RESULTING IN COOLER TEMPS ON WED.



MEANWHILE...PREDICTING THE MAX TEMPS FOR TODAY AND TUE WILL BE A

LITTLE TRICKY. THE MODELS INDICATED THAT HIGHS WILL BE COOLER

TODAY THAN YESTERDAY DUE TO INCREASED LOW LEVEL NLY FLOW. HAVE

CHOSEN TO KEEP THE INHERITED FORECAST...WHICH HAD TEMPS SLIGHTLY

HIGHER THAN MODEL GUIDANCE. LEFT THE INHERITED FORECAST FOR TUE

ALONE...ALSO. THE MODELS WERE SLIGHTLY WARMER FOR TUE. OUR

FORECAST SHOWED LITTLE CHANGE FROM TODAY. IT IS PROBABLE THAT

TODAY WILL END UP WARMER THAN YESTERDAY AND TUE WILL BE COOLER

THAN TODAY.



.LONG TERM...

THERE WAS SOME DISAGREEMENT IN THE MEDIUM RANGE SOLUTIONS FOR THE

THU/FRI TIME FRAME...RIDGE VERSUS TROF. FOR THIS WEEKEND...THE

MODELS WERE IN SOMEWHAT BETTER AGREEMENT. THE IDEA WAS THAT A

STRONG UPPER RIDGE WILL DOMINATE THE WEATHER PATTEN OVER THE

WESTERN USA. THE MAIN DIFFERENCES WERE IN THE DETAILS. THIS

WEEKEND COULD BE UNCOMFORTABLY WARM IF THE ECMWF SOLUTION

VERIFIES. ALSO...CANNOT RULE OUT THE POSSIBILITY OF TSTMS OVER

THE CASCADES THIS WEEKEND.



&&



.AVIATION...A BROAD FLAT UPPER LEVEL RIDGE WILL GIVE WESTERLY FLOW 

ALOFT AND A STABLE AIR MASS THROUGH TONIGHT. THE LOWER LEVELS OF THE 

AIR MASS IS MOIST AND WILL DRY MIDDAY.

 

WIDESPREAD LOW STRATUS AND FOG PRODUCING LIFR CEILINGS HAS MOVED 

INTO THE COASTAL ZONES AND IN THROUGH THE STRAIT OF JUAN DE FUCA. 

SURFACE DEW POINT TEMPERATURES ARE RATHER HIGH EARLY THIS MORNING IN 

THE STILL CLEAR INTERIOR AREAS...SO RADIATIONAL COOLING WILL LIKELY 

RESULT IN THE FORMATION OF LOW STRATUS AND AREAS OF FOG GIVING IFR 

TO LOW MVFR CEILINGS AND VISIBILITIES EARLY THIS MORNING THAT WILL 

PERSIST UNTIL MIDDAY...WHEN THE CLOUDS AND FOG WILL BURN BACK TO THE 

COASTAL WATERS. FOG IN THE INTERIOR OF WESTERN WASHINGTON WILL BE 

MAINLY CONFINED TO THE AREAS NEAR THE WATER WHERE SEA SURFACE 

TEMPERATURES ARE COOLER THAN THE DEW POINT TEMPERATURES. 



STRATUS WILL BURN BACK TO THE COASTLINE BY 19Z RESULTING IN GOOD VFR 

CONDITIONS THIS AFTERNOON AND THIS EVENING. 



WITH THE DEW POINT TEMPERATURES REMAINING HIGH TONIGHT...EXPECT A 

REPEAT PERFORMANCE ACROSS WESTERN WASHINGTON LATE TONIGHT INTO  

TUESDAY MORNING WITH FOG AND LOW STRATUS DEVELOPING INLAND AGAIN. 

ALBRECHT



KSEA...EXPECT STRATUS TO DEVELOP AROUND THE TERMINAL SHORTLY BEFORE 

12Z WITH CLOUD BASES AROUND 1000 FT AGL. STRATUS WILL BURN OFF 

AROUND 18Z GIVING GOOD VFR CONDITIONS THIS AFTERNOON AND TONIGHT 

THROUGH ABOUT 10Z...WHEN STRATUS WILL REDEVELOP. LIGHT NE WIND WILL 

TURN NW 10-14 KT MIDDAY THEN WILL TURN BACK TO THE N AND NE THIS 

EVENING. ALBRECHT



&&



.MARINE...A RIDGE OF HIGH PRES OVER THE COASTAL WATERS WILL SHIFT 

OFFSHORE AND STRENGTHEN THROUGH THURSDAY. AS THE RIDGE 

STRENGTHENS...EXPECT SMALL CRAFT ADVISORY NORTHWEST WINDS TO DEVELOP 

OVER THE COASTAL WATERS...ESPECIALLY BEYOND 10 NM...AND EXPECT SMALL 

CRAFT ADVISORY INFLOW TO DEVELOP DURING THE LATE AFTERNOON AND 

OVERNIGHT HOURS THROUGH THE STRAIT OF JUAN DE FUCA AND POSSIBLY 

ADMIRALTY INLET. SMALL CRAFT ADVISORY CONDITIONS WILL LIKELY DEVELOP 

AROUND 5 PM THIS AFTERNOON IN THE WATERS MENTIONED ABOVE.



EXPECT AREAS OF FOG AND PATCHY DRIZZLE THIS MORNING OVER THE COASTAL 

WATERS AND AT THE WEST END OF THE STRAIT OF JUAN DE FUCA. DEW POINT 

TEMPERATURES ARE WARMER THAN SEA SURFACE TEMPERATURES OVER THE 

STRAIT OF JUAN DE FUCA...THE NORTHERN INLAND WATERS...ADMIRALTY 

INLET...AND PORTIONS OF PUGET SOUND AND HOOD CANAL...HENCE PATCHY TO 

AREAS OF FOG OVER THE INLAND WATERS CAN ALSO BE EXPECTED THIS 

MORNING. FOG WILL BURN OFF MIDDAY THEN REFORM AGAIN LATE TONIGHT 

INTO TUESDAY MORNING. ALBRECHT



&&



.SEW WATCHES/WARNINGS/ADVISORIES...

WA...NONE.

PZ...NONE.



&&



$$



WWW.WEATHER.GOV/SEATTLE



FOR THE GRAPHICAL AFD...VISIT

WWW.WEATHER.GOV/SEATTLE/GAFD/LATEST_WEBAFD.HTML






FXUS66 KSEW 222153

AFDSEW



Area Forecast Discussion

National Weather Service Seattle WA

300 PM PDT Sun Oct 22 2017



.SYNOPSIS...Scattered showers will end tonight. Flooding will 

continue on a few rivers, but most are on the way down. Monday will 

have a few showers in the mountains, and Tuesday will be dry. After 

some light rain Wednesday, dry weather should return.

  

&&



.SHORT TERM...Radar shows scattered showers. These have had a few 

lightning strikes and some gusty winds, but they are waning and 

should be mostly done by sundown. Skies will clear somewhat 

overnight and patchy fog will develop. 



Monday and Tuesday now appear completely dry. Skies will become 

completely clear Monday night and the resulting fog late at night 

and Tuesday morning will be more extensive. Most of the fog will 

evaporate on both days and there will be a slow warming trend. Highs 

Monday will be 60-65, and they will be a few degrees higher Tuesday.



The weak system that will arrive from the northwest on Wednesday has 

been looking even weaker in recent model runs. The forecast is now 

for a chance of showers in the lowlands on Wednesday, with showers 

likely in the mountains. There will be considerably more clouds on 

Wednesday, so high temperatures will be 55-60. Burke



.LONG TERM...After the weak front Wednesday, an upper ridge will 

build off the coast, then slowly move inland through the weekend. 

This should give clear skies, dry weather, and highs mostly in the 

60s Thursday through Sunday. Burke



&&



.HYDROLOGY...While some showers remain on radar...the threat for 

heavy rain over the area has ended. Still...the effects of said rain 

are still being felt on some of the area rivers. Flood warnings 

remain in place...although the bulk of activity is trending 

downward. For example...while a flood warning remains in effect for 

the Skokomish River...current hydrographs indicate that waters have 

fallen below flood stage. As such...that particular warning will be 

allowed to expire upon the next FLS issuance. The Skykomish is in a 

similar situation. The Snoqualmie remains in minor flood stage but 

continues to trend downward...so that warning looks to remain in 

place into tonight. The Cowlitz at Randle looks like it has crested 

just over moderate flood stage and will start a downward trend soon. 

While the Snohomish remains below flood levels at the time of this 

writing...it is close and is still trending upward. That flood 

warning will remain in place...but will merit watching in the 

evening hours as the current trend does not really seem to fit well 

with current hydrograph forecast.



The flood watch in place for Lewis and Thurston counties remains in 

place due to a combination of the increased level of the Cowlitz and 

the continuing presence of showers there. As activity...both flood 

and showers...dwindles this evening...hard to imagine this watch not 

being pulled down at some point in the night.



All in all...general activity continues a downward trend as the area 

enters a phase where watches and warnings will slowly expire through 

the night.  SMR



&&



.AVIATION...West flow aloft over Western Washington this afternoon

will veer to northwest tonight and continue Monday, an an upper

ridge builds offshore and moves slowly toward the Pacific

Northwest coast. The air mass will gradually dry, especially at 

mid and upper levels, with low level onshore flow turning weakly 

offshore tonight.



We still have scattered light showers with BKN035-055 across

Western Washington. Isolated, brief thunderstorms are possible for

the next couple hours at the coast and over the Olympics. Relatively

clear skies and light winds tonight, combined the moist ground, 

should lead to patchy fog in the more fog-prone valleys late 

tonight and Monday morning. 



KSEA...Southwest wind 7-13 kt gusting 20 kt, easing this evening,

becoming southeast 4-8 kt tonight, then becoming northerly Monday

afternoon. VFR conditions with ceilings lifting above 6000 ft

later this evening. McDonnal



&&



.MARINE...Onshore flow this evening will turn weakly offshore 

late tonight and continue through Tuesday, as a ridge builds over 

the Pacific Northwest. Westerly swell 10 feet or higher will 

continue over the coastal waters and at the west entrance Strait 

of Juan de Fuca through Monday evening.



A weak cold front will move southeast across the area on 

Wednesday, with small craft advisory winds over some marine 

zones. Northerly offshore flow will follow the front Thursday and

Friday as a ridge builds over southern British Columbia. McDonnal



&&



.SEW WATCHES/WARNINGS/ADVISORIES...

WA...Flood Watch through Monday morning for Cascades of Pierce and 

     Lewis Counties-Southwest Interior.



PZ...Small Craft Advisory for hazardous seas until 11 PM PDT Monday 

     for Coastal Waters From Cape Flattery To James Island 10 To 

     60 Nm-Coastal Waters From Cape Flattery To James Island Out 

     10 Nm-Coastal Waters From James Island To Point Grenville 

     10 To 60 Nm-Coastal Waters From James Island To Point 

     Grenville Out 10 Nm-Coastal Waters From Point Grenville To 

     Cape Shoalwater 10 To 60 Nm-Coastal Waters From Point 

     Grenville To Cape Shoalwater Out 10 Nm.



     Small Craft Advisory for rough bar until 11 PM PDT Monday for 

     Grays Harbor Bar.



     Small Craft Advisory for hazardous seas until 5 PM PDT Monday 

     for West Entrance U.S. Waters Strait Of Juan De Fuca.



&&



$$



www.weather.gov/seattle



You can see an illustrated version of this discussion at

www.wrh.noaa.gov/sew/gafd/latest_webafd.html




FXUS66 KSEW 021737

AFDSEW



Area Forecast Discussion

National Weather Service Seattle WA

937 AM PST Sat Dec 2 2017



.SYNOPSIS...A cool showery low pressure system will move slowly 

across the region today through Sunday morning. Strong high 

pressure aloft will then prevail over the area through much of 

the upcoming week. Expect stagnant conditions to develop next

week. 



&&



.SHORT TERM...

There were numerous showers over the CWA at this time. So far,

haven't seen any lightning strikes offshore under the cold pool

aloft. Confidence in the threat of thunderstorms over the coast

was not high. Based on the latest model guidance, it appeared that

the threat (albeit low) will remain over the coastal waters, where

the instability will be the greatest. Will leave the forecast as 

is and monitor trends.



Still looking at modest snowfall amounts on Mount Rainier, where a

Winter Weather Advisory remains in effect. It looks like the snow

will be heaviest this afternoon through this evening. New snowfall

amounts will be in the 6-12 inch range on the Cascades in Pierce

and Lewis Counties, with the heaviest amounts occurring on Mount

Rainier.



Meanwhile, the low pressure system offshore will continue moving

east during the day today. It is expected to move across the

region tonight. By late Sunday morning, the upper level trough

will be over the Great Basin. An upper level ridge will build over

the area from the west on Sunday, resulting in a drying trend.



Expect the ridge to slowly strengthen over the Pacific Northwest

Sunday night and Monday. The ridge will be somewhat dirty;

therefore, expect primarily mid and high clouds to stream across

the CWA from the north.



.LONG TERM FROM THE PREV DISCUSSION...

The strong upper level ridge will continue to build over the Pac 

NW through next week. However, a strong low level inversion will 

likely lead to stagnant conditions across the interior lowlands. 

In this pattern we typically see fog developing overnight which 

may not completely burn off during the afternoon. This makes 

temperature forecasting very difficult with highs ranging from the

30s to mid/upper 40s, depending on the fog thickness. Light winds

and weak mixing may also lead to deteriorating air quality. Above

the inversion, in the mountains, it will be warmer with plenty of

sunshine. The ridge may weaken or flatten by next weekend but 

will stick with persistence for now. 33



&&



.AVIATION...A weak front will move through the area today with

southwest flow aloft. An upper trough will move over the area

tonight. The air mass is moist and stable. It will become unstable

near the coast in the afternoon. 



KSEA...MVFR low clouds should develop in the next few hours as a

front moves onshore. Low clouds will persist tonight and into

Sunday morning. Southeast wind 5-10 knots will become variable

this evening and then northerly later tonight. Schneider



&&



.MARINE...A weak front will bring marginal small craft advisory

strength winds to some of the waters today. There will also be

10-12 foot west swell over the Coastal Waters today. These will 

gradually subside below 10 feet tonight and Sunday. 



High pressure will move over the area Sunday and then shift inland

Monday with offshore flow developing. There will be some small

craft advisory strength northerly winds over the Coastal Waters

Sunday. These will ease and turn more easterly by Monday. Offshore

flow will continue Tuesday and Wednesday. Schneider





&&



.HYDROLOGY...River flooding is not expected the next 7 days.



&&



.SEW WATCHES/WARNINGS/ADVISORIES...

WA...Winter Weather Advisory until 4 AM PST Sunday for Cascades of 

     Pierce and Lewis Counties above 2000 feet.



PZ...Small Craft Advisory until 1 PM PST this afternoon for Admiralty 

     Inlet-Coastal Waters From Cape Flattery To James Island 10 

     To 60 Nm-Coastal Waters From Cape Flattery To James Island 

     Out 10 Nm-Coastal Waters From James Island To Point 

     Grenville 10 To 60 Nm-Coastal Waters From James Island To 

     Point Grenville Out 10 Nm-Coastal Waters From Point 

     Grenville To Cape Shoalwater 10 To 60 Nm-Coastal Waters 

     From Point Grenville To Cape Shoalwater Out 10 Nm-East 

     Entrance U.S. Waters Strait Of Juan De Fuca-West Entrance 

     U.S. Waters Strait Of Juan De Fuca.



     Small Craft Advisory from 6 AM to 6 PM PST Sunday for Coastal 

     Waters From Cape Flattery To James Island 10 To 60 Nm-

     Coastal Waters From James Island To Point Grenville 10 To 

     60 Nm-Coastal Waters From Point Grenville To Cape 

     Shoalwater 10 To 60 Nm.



     Small Craft Advisory for hazardous seas from 1 PM this afternoon 

     to 6 AM PST Sunday for Coastal Waters From Cape Flattery To 

     James Island 10 To 60 Nm-Coastal Waters From James Island 

     To Point Grenville 10 To 60 Nm-Coastal Waters From Point 

     Grenville To Cape Shoalwater 10 To 60 Nm-Coastal Waters 

     From Point Grenville To Cape Shoalwater Out 10 Nm.



     Small Craft Advisory for rough bar until 6 AM PST Sunday for 

     Grays Harbor Bar.



     Small Craft Advisory for hazardous seas from 1 PM to 4 PM PST 

     this afternoon for Coastal Waters From Cape Flattery To 

     James Island Out 10 Nm-West Entrance U.S. Waters Strait Of 

     Juan De Fuca.



     Small Craft Advisory for hazardous seas from 1 PM this afternoon 

     to 1 AM PST Sunday for Coastal Waters From James Island To 

     Point Grenville Out 10 Nm.



&&



$$



www.weather.gov/seattle




FXUS66 KSEW 291038

AFDSEW



Area Forecast Discussion

National Weather Service Seattle WA

238 AM PST Tue Jan 29 2019



.SYNOPSIS...An upper ridge and low level offshore flow will bring

dry weather through Tuesday. An upper low will pass to the south

on Wednesday for another dry day. A front will bring rain late 

Thursday into Friday. An upper trough will bring showery conditions

for the weekend with some drying possible by the middle of next 

week.



&&



.SHORT TERM /TODAY THROUGH THURSDAY/...High pressure and offshore

flow will lead to dry and stable conditions across Western

Washington through Wednesday. The south sound may see patchy fog

this morning, otherwise sunny conditions are expected. High temps

this afternoon will be mostly in the lower 50s. Expect similar

conditions on Tuesday with little change in the overall pattern.

Low clouds or fog will be more extensive on Wednesday due to weak

winds and poor mixing. The fog depth will be shallow and should

burn off during the afternoon. Expect sunny conditions up in the

mountains. 



The upper level ridge over the Pac NW will start to flatten as we

move into Thursday. Expect increasing clouds through the day as 

the next frontal system moves in from the west. We should see rain

across the region by late Thursday afternoon or evening as this 

system pushes inland. 33



.LONG TERM /FRIDAY THROUGH MONDAY/...Moist SW flow will prevail

through the end of the week for a wet period of weather across

Western WA. Snow levels will start high but should lower to around

4,000 feet Friday night for more snow in the mountains. We may see

a brief break on Saturday, then more showers Saturday night and

Sunday as an upper level trough nudges in. This system will be

cooler for lower snow levels (around 1,500 feet) and temperatures

trending a few degrees below normal. Cool and showery weather may

linger into Monday before this system exits. However, the timing

of this system's exit is off in the models. The models try to

build a ridge by midweek for another break in the weather. 33



&&



.AVIATION...High pressure remains in control with northeasterly flow 

aloft and at the surface. Mainly VFR conditions expected through the 

period with scattered high clouds. The exception would be for some 

patchy fog across the southwest interior, mainly at KOLM, this 

morning. 



KSEA...VFR conditions with scattered high clouds. N/NE winds 4 to 9 

kts. CEO 



&&



.MARINE...A 1034 mb ridge extends from central British Columbia

into Montana and Wyoming. This ridge, combined with a thermal 

trough of low pressure along the northern California and southern 

Oregon coast will result in moderate offshore flow through

Tuesday. Small craft advisories are in effect for east to 

northeast winds at the west entrance to the Strait of Juan de Fuca

and for the adjacent near-shore coastal waters. 



Winds will become lighter on Wednesday then become southerly on

Thursday as the ridge to the northeast of the area weakens and

shifts southeastward. A front will approach the waters from the

west Thursday night and Friday. Albrecht



&&



.HYDROLOGY...River flooding is not expected for the next 7 days.



&&



.SEW WATCHES/WARNINGS/ADVISORIES...

WA...None.

PZ...Small Craft Advisory until 4 PM PST this afternoon for Coastal 

     Waters From Cape Flattery To James Island Out 10 Nm-West 

     Entrance U.S. Waters Strait Of Juan De Fuca.



&&



$$



www.weather.gov/seattle