FXUS62 KKEY 201449 AFDKEY AREA FORECAST DISCUSSION FOR THE FLORIDA KEYS NATIONAL WEATHER SERVICE KEY WEST FL 1049 AM EDT FRI MAY 20 2011 .DISCUSSION... THE KEY WEST MORNING RAWINSONDE OBSERVATION REVEALED A VERY UNSTABLE VERTICAL PROFILE WITH LITTLE OR NO CONVECTIVE INHIBITION ENERGY. MOISTURE IN THE BOUNDARY LAYER HAS INCREASED SLIGHTLY DURING THE LAST 24 HOURS. SURFACE DEWPOINTS ARE NOW UP NEAR 73-74F AT MOST PLATFORMS. THIS IS TO BE EXPECTED AS SURFACE BREEZES HAVE FRESHENED...RESULTING IN MORE BOUNDARY LAYER MIXING/TURBULENCE AND ASSOCIATED UPWARD FLUXES OF HEAT/MOISTURE FROM THE SURROUNDING WARM OCEAN. SEA SURFACE TEMPERATURES ACROSS THE STRAITS OF FLORIDA AVERAGE 80-82F ACCORDING TO A RECENT ENHANCED MODIS SST COMPOSITE COURTESY OF THE SHORT-TERM PREDICTION RESEARCH AND TRANSITION CENTER. DATA FROM THE SAME VENUE REVEAL SEA SURFACE TEMPERATURES AVERAGING 82-84F OVER MOST OF FLORIDA BAY...HAWK CHANNEL...AND PORTIONS OF THE SOUTHEASTERN GULF OF MEXICO. THESE VALUES ARE ACTUALLY JUST ABOUT ON TARGET FOR THE THIRD WEEK IN MAY. THE PRIMARY LIMITING FACTOR FOR CUMULUS CONVECTION THIS MORNING IS DRY AIR ALOFT...AND IN PARTICULAR...DRY AIR WITHIN THE 925-700MB LAYER. DEWPOINT DEPRESSIONS EXCEEDING 10C EXTEND DOWNWARD AS LOW AS 900MB...OR ABOUT 3400FT ABOVE GROUND...NOT TOO FAR ABOVE CUMULUS CLOUD BASES. AS A CONSEQUENCE...YOUNG CUMULUS CLOUDS AND THEIR UPDRAFTS WILL FIGHT A MOSTLY LOSING BATTLE. THOSE WITH THE BEST CHANCE OF GROWING INTO SHOWERS MOST PROBABLY WILL BE ASSOCIATED WITH A BOUNDARY-LAYER CONVERGENCE ZONE. INDEED...THE ISOLATED SHOWERS EVIDENT AT PRESENT PER DOPPLER RADAR SCANS AND SATELLITE IMAGES ARE ASSOCIATED WITH CLOUD LINES IN THE SOUTHEASTERLY FLOW. FOR THIS AFTERNOON...DRY AIR IN THE LOWER TROPOSPHERE WILL LIMIT THE COVERAGE OF SHOWERS...DESPITE A VERY UNSTABLE ATMOSPHERE. LOWER- TROPOSPHERIC FLOW IS EXPECTED TO VEER FROM SOUTHEAST AT 10KT TO EAST. CURRENT FORECASTS HANDLE THE SITUATION WELL...AND NO UPDATES ARE ANTICIPATED AT THIS TIME. && .MARINE... MODERATE SOUTHEAST BREEZES WILL PERSIST THIS AFTERNOON WITH ISOLATED SHOWERS. && .AVIATION... SHORT-LIVED...30 MINUTES OR LESS...MVFR CEILINGS ARE A POSSIBILITY AT EYW AND MTH LATE TONIGHT INTO EARLY SATURDAY MORNING. DUE TO THE BRIEF NATURE OF POSSIBLE MVFR CEILINGS...ONLY VFR CONDITIONS WILL BE ADVERTISED IN THE TERMINAL FORECASTS. EAST TO SOUTHEAST WINDS OF 10 TO 15 KNOTS FROM JUST OFF THE SURFACE TO ABOUT 7 KFT WILL BECOME NORTHEAST TO EAST AND INCREASE TO 15 TO 20 KNOTS AFTER SUNSET. && .CLIMATE... ON THIS DATE IN KEYS WEATHER HISTORY...IN 1875...THE HIGH TEMPERATURE IN KEY WEST WAS ONLY 76 DEGREES. THIS SET THE DAILY RECORD FOR COOLEST HIGH TEMPERATURE MEASURED IN KEY WEST ON MAY 20TH...A RECORD WHICH STILL STANDS 136 YEARS LATER. && .PRELIMINARY POINT TEMPS/POPS... KEY WEST 87 78 87 78 / 10 10 10 10 MARATHON 89 78 89 78 / 10 10 10 10 && .KEY WATCHES/WARNINGS/ADVISORIES... FL...NONE. GM...NONE. && $$ PUBLIC/MARINE.........KASPER AVIATION/NOWCASTS.....BS DATA COLLECTION.......FUENTES VISIT US ON THE WEB AT WWW.WEATHER.GOV/KEYWEST  FXUS62 KKEY 090910 AFDKEY AREA FORECAST DISCUSSION FOR THE FLORIDA KEYS NATIONAL WEATHER SERVICE KEY WEST FL 410 AM EST THU JAN 9 2014 .DISCUSSION...IN THE MID AND UPPER LEVEL...(700-200 MB)...LATEST AVAILABLE IR IMAGERY OVERLAID WITH MODEL STREAMLINE ANALYSIS AS OF 300 AM CONTINUES TO DEPICT A ROBUST BROADLY CYCLONIC MID AND UPPER FLOW PATTERN ENCOMPASSING THE ENTIRE CONUS...CENTRAL AND NORTHERN OLD MEXICO THE GULF OF MEXICO...CUBA AND MOST OF THE BAHAMAS. AS A RESULT...DEEP SOUTHWESTERLIES ARE EVIDENT OVERHEAD OF THE KEYS ABOVE 650 MB....WITH 50 TO 75 KNOTS AT 250 MB. AT THE SURFACE AND IN THE LOWER LEVELS...LATEST AVAILABLE IR IMAGERY OVERLAID WITH MARINE AND LAND SURFACE OBSERVATIONS AND ANALYSIS AS OF 300 AM DETAIL THE MAIN AXIS OF A 1033-1035 MB ANTICYCLONIC RIDGE OF ARCTIC ORIGINS PRESENTLY ORIENTED FROM NEW JERSEY SOUTH SOUTHWEST TO THE CAROLINA PIEDMONT. CLOSER TO THE KEYS...THERE A WARM SURFACE FRONTAL BOUNDARY IS LOCATED FROM ANDROS ISLANDS SOUTHWEST TO ACROSS CUBA...BUT IT IS NOW SLOWLY APPROACHING THE ISLANDS FROM THE FLORIDA STRAITS. LAST EVENINGS 00Z SOUNDING ILLUSTRATED THAT A FRONTAL INVERSION WAS ALOFT ONLY AT ABOUT 700 FEET AGL LAST EVENING...BUT ATTM STRATUS BASES HAVE FALLEN EVEN LOWER OVER THE KEYS...WITH SOLID OVERCAST NOW AT 300-400 FEET AGL AT BOTH KEY WEST AND MARATHON AIRPORTS. LAST EVENINGS 00Z SOUNDING ALSO ILLUSTRATED THAT VERY GOOD LOWER LEVEL CONFLUENT FLOW REMAINED IN THE LOWER LEVELS...WITH NORTHEAST TO EAST WINDS INCREASE FROM NEAR 15 KNOTS RIGHT AT THE SURFACE...BECOMING MAINLY EASTERLY AND INCREASING UP TO AROUND 25 KNOTS FROM 500 TO 3000 FEET AGL. .CURRENTLY...AS OF 300 AM...RADAR AND SATELLITE IMAGERY STILL DETECT PATCHY LIGHT RAINFALL AND DRIZZLE RIGHT ALONG THE ISLAND CHAIN. MORE SHOWERY PRECIPITATION IS JUST OFFSHORE...WITH MOST OF IT CONCENTRATED ACROSS THE WESTERN FLORIDA STRAITS. TEMPERATURES OVER THE ISLANDS HAVE RISEN TO AROUND 70 DEGREES WITH DEWPOINTS IN THE UPPER 60S. GIVEN THE LOWER LEVEL FRONTAL INVERSION MENTIONED ABOVE AND SMALL DEWPOINT DEPRESSION...LOW CLOUD COVER SURROUNDS THE ISLANDS AND IMMEDIATE SHALLOW WATERS...AND IT CAN BE INFERRED THERE IS LIKELY A WIDESPREAD STRATUS DECK WITH BASES AOA 400 FEET AGL...AND THERE IS ANOTHER CLOUD DECK ABOVE THAT WITH BASES AOA FL030-050. C-MAN STATIONS ALONG THE FLORIDA REEF ARE STILL RECORDING SUSTAINED EAST WINDS NEAR 20 KNOTS AND GUSTY...WITH SMITH SHOAL LIGHT CLOSE TO 20 KNOTS ATTM. .FORECAST...TODAY THRU THIS EVENING...THE SURFACE WARM FRONTAL BOUNDARY WILL LIFT NORTH OF THE KEYS DURING THE MORNING HOURS...BUT CONFIDENCE OF EXACT TIMING IS SOMEWHAT ELUSIVE. UNTIL THAT TIME...A SOLID LOW CLOUD/STRATUS DECK WILL REMAIN OVER THE ISLANDS UNTIL THAT BOUNDARY MOVES TO THE NORTH. LATEST AVAILABLE MODIS SEA SURFACE ANALYSIS ILLUSTRATED THAT ALL SHALLOW WATERS AR AROUND 70 DEGREES OR HIGHER...SO ANY THREAT FOR FOG SHOULD BE MINIMAL ATTM...A FEW PATCHES OF SEA FOG COULD OCCUR ACROSS THE SHALLOWER WATERS INSIDE THE FIVE FATHOM LINE...BUT WILL LEAVE OUT OF THE FORECAST ATTM. THEREAFTER BY THIS AFTERNOON...CLOUD BASES SHOULD LIFT...BUT GIVEN THE PROXIMITY TO THE WARM FRONTAL BOUNDARY...AS WELL AS AVAILABLE MOISTURE IN THE LOWER TO MID LEVELS...COMBINED WITH JUST SOME WEAK IMPULSES ALOFT BETWEEN 500-200 MB...WILL STILL KEEP A GOOD CHANCE FOR SHOWERS WITH SOME ISOLATED THUNDERSTORMS THROUGH THIS AFTERNOON AND THIS EVENING. THE CLOUDY SKIES WILL ONLY GIVE WAY TO A FEW BREAKS IN THE AFTERNOON...GIVEN COVERAGES OF SHOWERS. TEMPERATURES AND HUMIDITY LEVELS WILL RETURN TO SLIGHTLY ABOVE SEASONAL LEVELS...WITH HIGHS NEAR 80 AND DEWPOINTS IN THE LOWER 70S. IN TERMS OF RAIN CHANCES...WILL MAINTAIN A HIGH CHANCE FOR SHOWERS WITH ISOLATED THUNDERSTORMS THIS AFTERNOON...WITH A MIDDLE OF THE ROAD CHANCE FOR SHOWERS TONIGHT. THE CENTER OF THE STRONG ARCTIC SURFACE RIDGE NOW OVER THE CAROLINA PIEDMONT THIS MORNING WILL MOVE QUICKLY NORTHEASTWARD...MOVING FROM NEAR CAPE HATTERAS THIS AFTERNOON TO ABOUT 40 NORTH 60 WEST DURING FRIDAY AFTERNOON...AND ONLY SLOWLY EASTWARD FRIDAY NIGHT. SO WOULD EXPECT BREEZY CONDITIONS TO END THIS MORNING WITH THE WARM FRONT CLOSE BY. DRIER AIR WILL EVENTUALLY FILTER IN SOMETIME AFTER MIDNIGHT TONIGHT...AND WOULD EXPECT ANOTHER BIT OF A SURGE AS THE AFOREMENTIONED WARM SURFACE FRONT DISSIPATES...AND THE LOCAL GRADIENT IS INFLUENCED PRIMARILY BY THE WESTERN ATLANTIC RIDGING. THEN ON SATURDAY THE NEXT DISTURBANCE MOVES RAPIDLY OUT OF THE PLAINS AND DRAGS A COLD FRONT SOUTHEASTWARDS INTO THE SOUTHEAST SATURDAY...REACHING NORTHERN AND CENTRAL FLORIDA SUNDAY BUT STALLING ON MONDAY. LOCAL WINDS SHOULD BOX AROUND TO SOUTHEAST TO SOUTH ON SATURDAY AND LIGHTEN UP...BECOMING SOUTH TO SOUTHWEST ON SATURDAY NIGHT...BEFORE BECOMING NORTHERLY ON SUNDAY...THEN CLOCKING MONDAY THROUGH TUESDAY. RAIN CHANCES WILL PROBABLY BE LOWEST ON SATURDAY GIVEN THE DRIER AIR...BUT LOW TO MID LEVEL MOISTURE AND LOWER LEVEL CONVERGENCE INCREASES JUST IN ADVANCE OF THE FRONTAL BOUNDARY ONCE AGAIN SATURDAY NIGHT THRU MONDAY. SO RAIN CHANCES WILL BE HELD AT 20 PERCENT FRIDAY THRU MONDAY...EXCEPT 10 PERCENT ON SATURDAY. HI AND LOW TEMPERATURES WILL CONTINUE SEVERAL DEGREES ABOVE NORMAL WITH ABOVE NORMAL HUMIDITY. EXTENDED...MONDAY NIGHT THRU WEDNESDAY...MODELS ARE NOT THAT SUPPORTIVE OF ANOTHER GOOD FRONTAL PASSAGE BUT DO SUGGEST THAT 1025 MB HIGH OVER CENTRAL TEXAS WILL BE STRONG ENOUGH TO PULL SURFACE BOUNDARY OVER FLORIDA SOUTHWARD DURING TUESDAY MORNING...SO BREEZY CONDITIONS WOULD BE ACCOMPANIED BY NEAR NORMAL DAYTIME HI AND NIGHTTIME LOWS IF THIS SOLUTION COMES TO FRUITION. SINCE ITS INDICATED BY THE MODELS...HAVE ADJUSTED TEMPERATURES TO AVERAGE FOR TUESDAY NIGHT AND WEDNESDAY THRU TUESDAY IN ASSOCIATION WITH THE APPROACHING FRONTAL SYSTEM. && .MARINE...A SMALL CRAFT ADVISORY WILL REMAIN IN PLACE THRU THE REST OF THIS MORNING FOR THE FLORIDA STRAITS...HAWK CHANNEL...THE WATERS OF THE SOUTHEASTERN GULF OF MEXICO AROUND REBECCA SHOAL AND THE DRY TORTUGAS...AND THE OFFSHORE GULF WATERS 20 TO 60 NM WEST OF MAINLAND MONROE COUNTY. ITS POSSIBLE THAT CAUTIONARY HEADLINES WILL REMAIN IN PLACE FOR ELEVATED SEAS IN THE FLORIDA STRAITS THIS AFTERNOON. HEADLINES OR ADVISORIES NOT EXPECTED TONIGHT AND FRIDAY...BUT CAUTIONARY HEADLINES MAY BE INSERTED FRIDAY NIGHT IN HAWK CHANNEL...THE OFFSHORE GULF WATERS...AND THE FLORIDA STRAITS FRIDAY NIGHT. WINDS AND SEAS EXPECTED TO BE BELOW HEADLINE OR ADVISORY STATUS OVER THE WEEKEND THROUGH MONDAY NIGHT. && .AVIATION... IFR TO LIFR CONDITIONS WILL BE A PERIODIC OCCURRENCE AT THE ISLAND TERMINALS OVERNIGHT TONIGHT...BEFORE BREAKING OUT AGAIN AROUND DAYBREAK ON THURSDAY. THOUGH SURFACE OBS WILL BE LIGHTER...STRONGER AND GUSTY ENE WINDS WILL BE SEEN JUST OFF THE SURFACE THROUGH 3KFT. && .CLIMATE...ON THIS DATE IN 1953, A RARE SEVERE THUNDERSTORM PRODUCED TWO MINUTES OF HAIL AND A 73 MPH GUST IN KEY WEST. THE RAINFALL FOR THE DAY WAS RECORDED AS 3.38 INCHES. THIS RAINFALL TOTAL STILL STANDS AS A DAILY RECORD FOR JANUARY 9TH. RAINFALL RECORDS IN KEY WEST DATE BACK TO 1871. && .KEY WATCHES/WARNINGS/ADVISORIES... FL...NONE. GM...SMALL CRAFT ADVISORY GMZ033&042>044-052>055-072>075 THRU 16Z && .PRELIMINARY POINT TEMPS/POPS... KEY WEST 77 73 78 75 / 50 40 20 20 MARATHON 79 74 82 75 / 50 40 20 20 && $$ PUBLIC/MARINE/GRIDS.............DAF AVIATION/NOWCASTS/CLIMATE.......MSB VISIT US ON THE WEB AT WWW.WEATHER.GOV/KEYWEST FOLLOW US ON FACEBOOK AND TWITTER AT... 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