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000
FXUS62 KKEY 271356
AFDKEY

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE KEY WEST FL
1000 AM EDT FRI MAR 27 2015

.DISCUSSION...IN THE MID AND UPPER LEVELS...(700-200 MB)...LATEST IR
IMAGERY AS OF 900 AM OVERLAID WITH MODEL STREAMLINE ANALYSIS DEPICTS
THE AXIS OF A DEEP LATE SEASON POLAR TROUGH SITUATED FROM EASTERN
ONTARIO SOUTH SOUTHWEST TO SOUTH TEXAS. WELL SOUTHEAST OF
THAT...THE NORTHWEST EXTENT OF A DEEP AND WARM ANTICYCLONE REACHED
SOUTH FLORIDA AND THE FLORIDA KEYS FROM THE LOWER CENTRAL CARIBBEAN
SEA...BUT LOWER HEIGHTS ARE APPROACHING THE KEYS ATTM ACCOMPANIED BY
INCREASING LOBES OF MIDDLE LEVEL POSITIVE VORTICITY ADVECTION (PVA)
AT 500 MB MOVING ACROSS THE SOUTHEASTERN GULF OF MEXICO. SATELLITE
AND SEA SURFACE OBSERVATIONS IN THE CENTRAL GULF ALSO DO DEPICT SOME
LINEAR CONVECTION IN THE EASTERN AND SOUTH CENTRAL GULF OF MEXICO
ATTM.

AT THE SURFACE AND IN THE LOWER TO MID LEVELS...SURFACE TO 700
MB...LATEST AVAILABLE SATELLITE IMAGERY OVERLAID WITH MARINE AND
LAND SURFACE OBSERVATIONS AND ANALYSIS AS OF 900 AM...DETECT A LATE
SEASON COLD FRONT FROM OFF OF THE NEW ENGLAND COAST SOUTH SOUTHWEST
AND BISECTING THE CENTRAL GULF OF MEXICO. THE 12Z SOUNDING AT KEY
WEST ILLUSTRATED A FAIRLY MOIST WITH PWAT(PRECIPITABLE WATER) AT
1.58 INCHES YET UNSTABLE LOWER TO MIDDLE TROPOSPHERE WITH SURFACE TO
3 KM LAPSE RATES OF 7.7 DEGREES CELSIUS PER KILOMETER. THE PROFILE
ALSO CONSISTED OF GENTLE TO FRESH SOUTHWEST TO WEST WINDS JUST OFF
THE SURFACE...BACKING MORE TO THE SOUTHWEST ABOVE 900 MB...REACHING
ABOUT 50 KNOTS AT 500 MB. YET DRY AIR ASSOCIATED WITH THE CARIBBEAN
ANTICYCLONE REMAINS ABOVE 700 MB.

.CURRENTLY...AS OF 900 AM...SKIES ARE PARTLY CLOUDY...WITH A FEW
REVERSE DIRECTION CLOUD LINES DEVELOPING ACROSS THE MIDDLE FLORIDA
KEYS AND THE FLORIDA STRAITS. TEMPERATURES ACROSS THE ISLANDS ARE
ALREADY NEAR 80 DEGREES WITH DEWPOINTS IN THE LOWER TO MID 70S. KEY
WEST RADAR DETECTS THE LEADING EDGE OF SCATTERED SHOWERS NOW MOVING
INTO GMZ-034...ABOUT 20 NM WEST OF THE DRY TORTUGAS.

.SHORT TERM (REST OF TODAY)...THE AXIS OF THE COLD CORE MID AND
UPPER LEVEL TROUGH WILL CONTINUE ITS STEADY MIGRATION EASTWARD
THROUGH TODAY...MOVING ACROSS THE FLORIDA PENINSULA TONIGHT AND ONLY
SLOWLY EAST OF FLORIDA THROUGH THE UPCOMING WEEKEND. THE SURFACE
COLD FRONT OVER THE CENTRAL GULF WILL MOVE SLOWLY EASTWARD THROUGH
THE AFTERNOON AND EVENING...NOT ACTUALLY MOVING ACROSS THE KEYS
UNTIL BETWEEN 06 AND 12Z. GIVEN ABOVE MID-LEVEL DYNAMICS AND LARGE
AMOUNT OF PREFRONTAL CONVECTION NOW OVER THE CENTRAL GULF OF
MEXICO...MID LEVEL HEIGHTS WILL FALL THROUGH THE REST OF THE MORNING
AND THIS AFTERNOON AND LARGE SCALE LIFT WILL ALLOW FOR IN SITU
DEVELOPMENT OF SHOWERS AND ISOLATED THUNDERSTORMS LATER IN THE
AFTERNOON...WITH THE CRUX OF THIS ACTIVITY DURING THIS EVENING.
GIVEN THE CURRENT SOUNDING AND THE PROFILE OF AVAILABLE FORECAST
SOUNDINGS WE ANTICIPATE LOCALLY STRONG WIND GUSTS...IN EXCESS OF 40
KNOTS WILL BE POSSIBLE IN THE STRONGER SHOWERS AND ISOLATED
THUNDERSTORMS. THESE WILL ALSO BE ACCOMPANIED BY BRIEF PERIODS OF
HEAVY RAINFALL AND OCCASIONAL LIGHTNING.

TEMPERATURES THIS AFTERNOON IN ADVANCE OF THIS ACTIVITY WILL LIKELY
CLIMB TO NEAR RECORD...THE MIDDLE TO UPPER 80S. OUTSIDE OF SHOWERS
AND THUNDERSTORMS GENTLE SOUTH TO SOUTHWEST WINDS WILL CLOCK TO
BETWEEN WEST AND NORTHWEST THIS AFTERNOON AND FRESHEN TO BETWEEN 15
AND 20 KNOTS. SCATTERED TO NUMEROUS SHOWERS AND SCATTERED
THUNDERSTORMS WILL MOVE ACROSS THE KEYS DURING THIS EVENING. BREEZY
CONDITIONS ARE EXPECTED BY LATE THIS AFTERNOON AND EVENING BUT MAY
LULL AT TIMES...WITH WINDS CLOCKING TO NORTH AND WINDY CONDITIONS
EXPECTED AFTER FROPA LATE TONIGHT.

&&

.MARINE...A COLD FRONT WILL MOVE ACROSS THE EASTERN GULF OF MEXICO
TODAY...PASSING THROUGH THE KEYS EARLY SATURDAY MORNING. SCATTERED
SHOWERS AND ISOLATED THUNDERSTORMS WILL DEVELOP AHEAD OF THE COLD
FRONT LATE THIS AFTERNOON AND EVENING. THESE SHOWERS AND
THUNDERSTORMS WILL PRODUCE LOCALLY STRONG WIND GUSTS IN EXCESS OF 40
KNOTS...LOCALLY HIGHER SEAS...AND OCCASIONAL LIGHTNING STRIKES...AS
WELL AS POOR VISIBILITY IN BRIEF HEAVY RAINFALL. SMALL CRAFT WILL
NEED TO EXERCISE CAUTION ACROSS ALL WATERS BY LATE THIS AFTERNOON AS
GENTLE TO MODERATE WINDS VEER FROM SOUTHWEST THIS MORNING TO BETWEEN
WEST AND NORTHWEST THIS AFTERNOON AS THE INCREASE TO BETWEEN 15 TO
20 KNOTS LATE. A SMALL CRAFT ADVISORY WILL BE LIKELY ACROSS ALL
WATERS AFTER MIDNIGHT TONIGHT WITH FRESH TO STRONG NORTHWEST TO
NORTH WINDS...SUSTAINED AS HIGH AS 25 KNOTS. THESE SMALL CRAFT
ADVISORIES ARE EXPECTED FROM MIDNIGHT THROUGH SATURDAY NIGHT ON ALL
KEYS WATERS...AND POSSIBLY THROUGH SUNDAY OVER THE STRAITS OF
FLORIDA.

&&
.AVIATION...
UNTIL 00Z/28TH...OUTSIDE OF A SPELL OR TWO OF MVFR CONDITIONS...VFR
CONDITIONS WILL PREVAIL AT KEY WEST AND MARATHON TERMINAL THROUGH AT
LEAST MIDDAY. THEREAFTER...THE PROBABILITY OF MVFR CONDITIONS WILL
SLOWLY INCREASE...WHILE SOUTH TO SOUTHWEST WINDS SLOWLY INCREASE AND
BECOME SOUTHWEST TO WEST AT 10 TO 15 KNOTS WITH GUSTS NEAR 20 KNOTS
BY LATE THIS AFTERNOON.

&&

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

&&

$$

PUBLIC/MARINE/FIRE/CLIMATE/DIGITAL...FUTTERMAN
AVIATION/NOWCASTS....................APA
DATA ACQUISITION/UPPER AIR...........VICKERY

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