Area Forecast Discussion
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000
FXUS62 KKEY 110112
AFDKEY

AREA FORECAST DISCUSSION FOR THE FLORIDA KEYS
NATIONAL WEATHER SERVICE KEY WEST FL
915 PM EDT THU JUL 10 2014

.DISCUSSION...IN THE MID AND UPPER LEVELS...(700-200 MB)...LATEST
AVAILABLE IR IMAGERY OVERLAID WITH MODEL STREAMLINE ANALYSIS AS OF
800 PM DEPICT WEAKLY DIFFLUENT FLOW AT 200 MB NEAR THE KEYS...DUE TO
DIFFERENCE A DEEP UPPER RIDGE CENTERED NEAR 70 WEST 30 NORTH AND A
WESTWARDLY MIGRATING TROPICAL UPPER TROPOSPHERIC TROUGH (TUTT)
LOW...WHICH IS SOUTH OF THE UPPER RIDGE...AND CENTERED NEAR THE
WINDWARD PASSAGE. IN THE MID LEVELS...WEAK RIDGING CONTINUED ACROSS
SOUTH FLORIDA AND THE KEYS...WITH MORE ESTABLISHED RIDGING CENTERED
OVER THE WESTERN ATLANTIC.

ANALYSIS OF THE SURFACE AND LOWER LEVEL FEATURES...SURFACE TO 700
MB...DETAILS THE NEAR 1020 MB SOUTHWESTERN PERIPHERY NOSING ACROSS
SOUTH FLORIDA AS PART OF AN ATLANTIC SURFACE RIDGE CENTERED OVER THE
NORTH CENTRAL ATLANTIC OCEAN. THE LATEST MIMIC-DERIVED TOTAL
PRECIPITABLE WATER (PWAT) INDICATES THE LEADING EDGE OF A NARROW
SWATH OF DRIER AIR IN THE LOWER TO MIDDLE LEVELS IS APPROACHING THE
KEYS FROM THE NORTHERN BAHAMAS ATTM. THE 00Z EVENING SOUNDING
ILLUSTRATED A FAIRLY MOIST GENTLE MOSTLY EAST FLOW FROM THE SURFACE
TO 700 MB...BUT BECOMING VARIABLE UP TO 500 MB.

.CURRENTLY...SKIES ARE PARTLY TO MOSTLY CLOUDY FROM THE SEVEN MILE
BRIDGE AND SURROUNDING WATERS WESTWARD...BUT PARTLY CLOUDY TO THE
EAST OF THAT...WITH MIDDLE AND HIGHER CLOUD DEBRIS EVIDENT FROM THE
IMAGERY. BUT KEY WEST RADAR DOES SHOW SMALL ISOLATED SHOWERS AND
STORMS ARE JUST DOWNSTREAM OF ANDROS ISLAND AND APPROACHING THE CAY
SAL BANK. TEMPERATURES OVER THE ISLANDS ARE IN THE LOWER 80S WITH
DEWPOINTS IN THE MIDDLE TO UPPER 70S. C-MAN STATIONS ALONG THE REEF
ARE RECORDING NORTH TO EAST WINDS BETWEEN 5 AND 10 KNOTS...EXCEPT
STILL 10 TO 15 KNOTS IN VICINITY OF SHOWER ACTIVITY ACROSS THE DRY
TORTUGAS.

.FORECASTS...OVERNIGHT...THE LEADING EDGE OF THE SAHARAN DUST WHICH
IS NOW WELL DELINEATED BY WATER VAPOR AND IR IMAGERY...WILL CONTINUE
ADVANCES WESTWARD OVERNIGHT...WITH DRIER AIR ACROSS THE SERVICE AREA
FOR TONIGHT AND TOMORROW. LATEST AVAILABLE MODEL FORECAST SOUNDINGS
DO ILLUSTRATE ALMOST A ONE HALF INCH DROP IN TOTAL PWAT BY 12Z.
NEVERTHELESS...THE LOWER TO MID LEVEK INFUSION OF DRIER AIR WILL
STILL NOT BE ENOUGH TO ELIMINATE THE THREAT FOR RAIN CHANCES...GIVEN
THE OVERALL TYPICAL INSTABILITY EXHIBITED BY THE 00Z EVENING
SOUNDING. IN ADDITION...SLIGHT INTENSIFICATION THE RIDGING TO THE
NORTH ACROSS THE PENINSULA IS INDICATED BY THE MODELS...ALLOWING FOR
GENTLE TO MODERATE BREEZES OVERNIGHT. THIS WOULD ALSO AID IN BETTER
LOW LEVEL CONVERGENCE DESPITE THE DRIER AIR...THEREFORE WILL LEAVE
IN A SLIGHT CHANCE FOR SHOWERS AND THUNDERSTORMS OVERNIGHT. ONLY
UPDATE WILL BE TO REMOVE THE TRANSITIONAL WORDING FROM THE ZONES AND
COASTAL FORECASTS.

&&

.MARINE...
WINDS WILL INCREASE OVERNIGHT...BECOMING GENTLE TO MODERATE OUT OF
THE EAST TO SOUTHEAST TONIGHT...BUT NO HEADLINES OR ADVISORIES ARE
ANTICIPATED ATTM.

&&

.AVIATION...VFR CONDITIONS WILL PREVAIL AT BOTH THE KEY WEST AND
MARATHON ISLAND TERMINALS. VERY BRIEF IFR/MVFR CIGS AND/OR VIS
POSSIBLE IN ANY ISOLATED SHOWER THAT MANAGES TO IMPACT EITHER OR
BOTH TERMINALS BUT CHANCES TO REMOTE TO INCLUDE IN TAF ATTM.

&&

.KEY WATCHES/WARNINGS/ADVISORIES...
FL...NONE.
GM...NONE.
&&

$$

PUBLIC/MARINE/GRIDS.........KASPER/FUTTERMAN
AVIATION/NOWCASTS...........FUTTERMAN
DATA COLLECTION/UPPER AIR...BWC

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