FXUS66 KSEW 311606

AFDSEW



AREA FORECAST DISCUSSION

NATIONAL WEATHER SERVICE SEATTLE WA

900 AM PDT FRI JUL 31 2015



.SYNOPSIS...A STRONG UPPER LEVEL RIDGE BRINGING HOT TEMPERATURES 

WILL REMAIN OVER THE PACIFIC NORTHWEST THROUGH EARLY NEXT 

WEEK...WHEN IT WILL WEAKEN AND SHIFT EASTWARD. AN UPPER LEVEL TROUGH 

WILL MOVE OVER THE AREA BY THE MIDDLE OF NEXT WEEK. TEMPERATURES 

WILL MODERATE TO NEAR NORMAL WITH A CHANCE OF A FEW SHOWERS 

WEDNESDAY THROUGH THE END OF NEXT WEEK.

 

&&



.SHORT TERM...WITH A STRONG UPPER LEVEL RIDGE AXIS ALMOST DIRECTLY 

OVERHEAD AND 500 MB HEIGHTS AROUND 590 DM OVER WESTERN WA...EXPECT 

TEMPS TODAY TO BE THE WARMEST OF THE BUNCH...WITH A LARGE SWATH OF 

HIGHS IN THE 90S SEATTLE SOUTHWARD. HIGHS AROUND THE REST OF THE 

AREA WILL ALSO BE WELL ABOVE NORMAL. THE SURFACE FLOW IS LIGHT 

NORTHERLY AND ONSHORE.



ON SATURDAY AND SUNDAY THE UPPER LEVEL HEIGHTS WILL SLOWLY FALL AND 

THE RIDGE WILL BEGIN TO WEAKEN AND MOVE SLOWLY EASTWARD. UPPER LEVEL 

HEIGHTS WILL DROP A FEW DMS EACH DAY. TEMPERATURES WILL LIKELY DROP 

A COUPLE DEGREES EACH DAY AS WELL...BUT STILL REMAIN VERY WARM. LOWS 

EARLY SATURDAY AND SUNDAY MORNINGS IN THE PUGET SOUND AREA WILL 

REMAIN QUITE WARM TOO...IN THE MID 60S. SURFACE FLOW WILL REMAIN 

LIGHT TO MODERATE NORTHERLY AND ONSHORE THROUGH EARLY SUNDAY.



RECENT MODELS HAVE BEEN INDICATING THAT A MARINE PUSH WILL DEVELOP 

SUNDAY EVENING...AROUND THE TIME THAT THE HEAT ADVISORY EXPIRES. 

GALES ARE POSSIBLE IN THE STRAIT AND MARINE AIR WILL INFILTRATE THE 

INTERIOR LOWLANDS. THIS WILL START A TREND OF MODERATING 

TEMPERATURES.  JSMITH



.LONG TERM...THE RIDGE WILL WEAKEN MORE AND SHIFT EWD OVER THE 

ROCKIES BY MONDAY AS AN UPPER TROUGH DROPS SE TOWARD THE PAC NW. 

LOWER HEIGHTS AND ONSHORE FLOW MEAN HIGHS WILL STRUGGLE TO REACH THE 

LOW 80S AROUND PUGET SOUND...WITH 70S ACROSS THE N INTERIOR AND 

STRAIT. HIGHS AT THE COAST MAY STRUGGLE TO REACH 70. 



MODELS TAKE THE UPPER LOW SWD OFF THE PAC NW AND SRN B.C. COASTS ON 

TUESDAY. ONSHORE FLOW WILL BE STRONGER AND HIGH TEMPERATURES WILL 

FINALLY FALL TO THE 70S OVER ALL THE LOWLANDS...NEAR OR EVEN 

SLIGHTLY BELOW NORMAL. THE LOW COULD MOVE CLOSE ENOUGH TO THE COAST 

TO BRING A FEW SHOWERS TO THE COAST AND MOUNTAINS BY WEDNESDAY. BY 

THURSDAY AND FRIDAY THERE MAY BE A BETTER CHANCE OF SHOWERS IF THE 

LOW MOVES CLOSER TO THE AREA AS SOME MODELS INDICATE. HIGHS WILL BE 

NEAR OR EVEN BELOW NORMAL TOWARD THE END OF NEXT WEEK. MERCER/JSMITH



&&



.AVIATION...A BROAD UPPER RIDGE WILL REMAIN OVER THE REGION 

THROUGH TONIGHT WITH LIGHT WESTERLY FLOW ALOFT. THE AIR MASS WILL BE 

DRY AND STABLE. 



THERE IS A THIN LINE OF SHALLOW STRATUS ALONG THE WASHINGTON COAST 

AND IN THE WESTERN STRAIT OF JUAN DE FUCA THIS MORNING...BRINGING 

LOCAL IFR CONDITIONS. THIS SHOULD RETREAT OFF THE COAST BY LATE 

MORNING...THEN RETURN TONIGHT. OTHERWISE CLEAR SKIES WILL 

CONTINUE. 



KSEA...NORTH TO NORTHWEST WIND MOSTLY 4-10 KT.



&&



.MARINE...PERSISTENT HIGH PRESSURE OFFSHORE AND LOWER PRESSURE EAST 

OF THE CASCADES WILL MAINTAIN LIGHT NORTHWEST PRESSURE GRADIENTS 

ACROSS THE FORECAST AREA. SMALL CRAFT ADVISORY WESTERLIES ARE LIKELY 

IN THE CENTRAL AND EASTERN STRAIT OF JUAN DE FUCA THIS EVENING. 

ONSHORE FLOW WILL INCREASE THIS WEEKEND...AND GALE FORCE WESTERLIES 

ARE POSSIBLE SATURDAY NIGHT AND SUNDAY NIGHT.



&&



.FIRE WEATHER...A CRITICAL PERIOD FOR FIRE WEATHER CONTINUES OVER 

ALL OF WESTERN WASHINGTON...WITH VERY DRY AIR THROUGH MOST OF THE 

DEPTH OF THE TROPOSPHERE THROUGH SATURDAY AFTERNOON. IN 

ADDITION...ELEVATED MOUNTAIN LOCATIONS ARE FEELING THE ADDED EFFECT 

OF MID-LEVEL INSTABILITY...WITH BOTH MID-LEVEL AND HIGH-LEVEL HAINES 

5 CONDITIONS CONTINUING INTO SATURDAY EVENING. MODIS IMAGERY AND 

VISIBLE SATELLITE IMAGERY BOTH INDICATE A PICKUP IN THE ACTIVITY 

LEVEL OF ONGOING FIRES IN BOTH OLYMPIC AND NORTH CASCADES NATIONAL 

PARKS SINCE YESTERDAY. WILL KEEP THE RED FLAG WARNING GOING FOR 

ELEVATIONS ABOVE 2000 FEET UNTIL SATURDAY EVENING CONSIDERING BOTH 

THE DRYNESS OF AIR MASS AND THE EFFECTS OF MID-LEVEL INSTABILITY. 

THIS IS THE KIND OF WEATHER SETUP THAT HELPS SMALL FIRES GROW TO 

BECOME LARGE FIRES.		HANER



&&



.SEW WATCHES/WARNINGS/ADVISORIES...

WA...HEAT ADVISORY REMAINS IN EFFECT TIL 8 PM SUNDAY FOR PARTS OF	   

     THE PUGET SOUND REGION AND SOUTHWEST INTERIOR.



     RED FLAG WARNING IN EFFECT TIL 10 PM SATURDAY NIGHT FOR THE

	 CASCADES AND OLYMPICS ABOVE 2000 FEET.



PZ...SMALL CRAFT ADVISORY COASTAL WATERS EXCEPT ZONE 150...CENTRAL

     STRAIT OF JUAN DE FUCA...EAST ENTRANCE STRAIT.



&&



$$



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