Area Forecast Discussion
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000
FXUS62 KKEY 050847
AFDKEY

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE KEY WEST FL
447 AM EDT TUE MAY 5 2015

.DISCUSSION...
AN UPPER-LEVEL COMPOSITE ANALYSIS EARLY THIS MORNING REVEALS A SHARP
SOUTHERN-STREAM SHORT-WAVE TROUGH OVER THE GULF BASIN...WITH AN
EXPANSIVE REGION OF LARGE-SCALE LIFT CENTERED MAINLY ABOVE 700MB FROM
THE SOUTHEASTERN GULF OF MEXICO TO THE BAHAMAS. AT LOWER
ALTITUDES...AN EXPANSIVE ANTICYCLONE WAS CENTERED OVER THE WESTERN
NORTH ATLANTIC JUST OFFSHORE THE CAROLINAS. THE FLORIDA KEYS LIE AT
THE EXTREME SOUTHERN FLANK OF THIS SYSTEM...JUST NORTH OF AN OLD
FRONTAL SHEAR LINE...WHICH SEPARATES TROPICAL AIR RICH IN MOISTURE
FROM MUCH DRIER...MODIFIED CONTINENTAL AIR. THIS EAST-WEST REMNANT
FRONTAL ZONE AND ITS ASSOCIATED CYCLONIC VORTICITY/CONVERGENCE HAS
BEEN SERVING AS A FOCUS FOR SHOWERS AND THUNDERSTORMS...AND IS MOVING
SLOWLY NORTHWARD. IN FACT...RAIN IS JUST NOW ENTERING MANY ISLAND
COMMUNITIES BETWEEN GRASSY KEY AND KEY WEST.

CURRENTLY...AIR TEMPERATURES IN MOST KEYS COMMUNITIES ARE HOLDING IN
THE MID 70S...EXCEPT LOWER 70S WHERE RAIN-COOLED. DEWPOINT
TEMPERATURES AVERAGE IN THE UPPER 60S...BUT WILL BE INCHING UPWARD
LATER THIS MORNING. WINDS ACROSS THE KEYS TURNED NORTHEAST AND
SLACKENED OVERNIGHT. HOWEVER...FRESH BREEZES PERSIST ACROSS MOST OF
THE COASTAL WATERS.

FORECASTS -- TODAY SHOULD BE THE SECOND CLOUDY AND RAINY DAY WITHIN A
WEEK. ALTHOUGH WE ARE NOT EXPECTING THE KIND OF RAINFALL TOTALS WE
SAW LAST WEDNESDAY...SLOW-MOVING SHOWERS AND STORMS MAY DELIVER UP TO
1-2 INCHES LOCALLY. AIR TEMPERATURES SHOULD BE LIMITED TO NEAR OR
JUST ABOVE 80F OWING TO WIDESPREAD CLOUD COVER AND RAIN. A SURFACE
TROUGH DEVELOPING BENEATH A FAVORABLE UPPER-AIR PATTERN OVER THE
NORTHERN BAHAMAS...SOUTH OF A WEAKENING HIGH CELL WILL RESULT IN
SLACKENING BREEZES LOCALLY.

SHOWER AND THUNDERSTORM CHANCES SHOULD GRADUALLY DECREASE TONIGHT
THROUGH WEDNESDAY NIGHT...AS FORCING FOR ASCENT DIMINISHES.
THEREAFTER...NEAR-AVERAGE SLIGHT RAIN CHANCES WILL RETURN...WITH
DAILY RAINFALL PATTERNS INFLUENCED BY INTERACTION BETWEEN LOW-LEVEL
FLOW...TERRAIN-INDUCED DIFFERENTIAL HEATING...AND MOISTURE NUANCES.
AIR TEMPERATURES BOTH DURING THE DAY AND AT NIGHT WILL INCREASE AS
ABUNDANT SUNSHINE RETURNS THANKS TO DEVELOPING LARGE-SCALE SUBSIDENCE
IN WAKE OF THE UPPER TROUGH.
&&

.MARINE...
A LARGE HIGH PRESSURE SYSTEM OVER THE WESTERN NORTH ATLANTIC WILL
SHIFT EASTWARD...AND WEAKEN TODAY AND TONIGHT... WHILE A TROUGH OF
LOW PRESSURE MOVES NEAR THE FLORIDA KEYS. ANOTHER AREA OF HIGH
PRESSURE GRADUALLY WILL PRESS SOUTHWARD OVER THE EASTERN GULF OF
MEXICO AND FLORIDA KEYS FROM WEDNESDAY THROUGH SATURDAY.
&&

.AVIATION...
SHOWERS AND THUNDERSTORMS CAN BE EXPECTED PERIODICALLY AT BOTH THE
KEY WEST AND MARATHON TERMINALS AND VICINITY DURING THE EARLY MORNING
HOURS PROCEEDING AND FOLLOWING SUNRISE...BEGINNING NEAR 09Z AND
TAPERING OFF AFTER 17Z. THIS WILL BRING PERIODS OF MVFR AND POSSIBLE
SHORT PERIODS OF IFR VISIBILITY IN THE HEAVIER DOWNPOURS.
ADDITIONALLY...WIND GUSTS APPROACHING 30 KNOTS CAN BE EXPECTED IN THE
VICINITY OF THUNDERSTORMS. AFTER NOON...VFR CONDITIONS CAN BE
EXPECTED TO PREVAIL AT BOTH TERMINALS. SURFACE WINDS WILL BE
GENERALLY...OUTSIDE OF THUNDERSTORMS...EASTERLY NEAR 10 KNOTS.
&&

.CLIMATE...
ON THIS DATE IN FLORIDA KEYS WEATHER HISTORY...MAY 5...THE CINCO DE
MAYO SPOUTBREAK OF 2004 OCCURRED. SEVERAL WATERSPOUTS WERE REPORTED
BY BOATERS...PILOTS...RESIDENTS...AND TOURISTS BETWEEN KEY WEST AND
THE MARQUESAS KEYS. NATIONAL WEATHER SERVICE OBSERVERS IDENTIFIED 11
SEPARATE FUNNELS FROM THEIR TEMPORARY FACILITY AT KEY WEST
INTERNATIONAL AIRPORT...WITH SPOUTS REPORTED NORTH...WEST...AND
SOUTHWEST OF KEY WEST BETWEEN 400-600 PM.

THE DAILY RECORD RAINFALL FOR TODAY AT KEY WEST IS 2.10 INCHES...
RECORDED IN 1968.
&&

.PRELIMINARY POINT TEMPS/POPS...
KEY WEST  81  73  83  75 / 80 50 40 30
MARATHON  82  73  85  75 / 80 50 40 30
&&

.KEY WATCHES/WARNINGS/ADVISORIES...
FL...NONE.
GM...SMALL CRAFT ADVISORY IN EFFECT FOR...
     GMZ032-GMZ033-GMZ034-GMZ035-GMZ042-GMZ043-GMZ044-
     GMZ052-GMZ053-GMZ054-GMZ055-GMZ072-GMZ073-GMZ074-
     GMZ075.
&&

$$

PUBLIC/MARINE.........KASPER
AVIATION/NOWCASTS.....DEVANAS
DATA COLLECTION.......DEVANAS

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