FXUS62 KKEY 230933
AFDKEY
AREA FORECAST DISCUSSION FOR THE FLORIDA KEYS
NATIONAL WEATHER SERVICE KEY WEST FL
533 AM EDT THU MAY 23 2013
.DISCUSSION...THE RADAR REMAINS ECHO FREE THIS MORNING SAVE FOR A FEW
LEFTOVER BOUNDARIES LUNGING NORTHWARD. CLOUD COVER RANGES FROM MOSTLY
CLEAR TO PARTLY CLOUDY UNDERNEATH THE SAME TRANSIENT BOUNDARIES.
TEMPERATURES HAVE COOLED TO NEAR 80 DEGREES...AND WINDS HAVE BEEN
MOSTLY VARIABLE AND UNDER 10 KNOTS. THE UPPER LEVEL TROUGH TO THE
EAST OF FLORIDA HAS BECOME MORE PROGRESSIVE AND CONTINUES TO PUSH
NORTHEAST. WATER VAPOR IMAGERY AND WIND PROFILES FROM LAST EVENINGS
RAOB SOUNDING REVEAL WESTERLY FLOW IN THE MID TO UPPER LEVELS. AT THE
SURFACE...THE WESTERN EXTENSION OF THE BERMUDA HIGH PRESSURE CELL
REMAINS FRACTURED IN ITS REACH ACROSS FLORIDA.
.SHORT TERM (TODAY THROUGH SATURDAY)...BASED ON YESTERDAYS WINNING
BATTLE OVER THE DRY AIR...A PERSISTENCE FORECAST SEEMS REASONABLE FOR
TODAY. IN FACT...THERE MAY BE LESS DRY AIR IN THE MID LEVELS TODAY AS
THE UPPER TROUGH PROPAGATES AWAY. WIND AND LOW LEVEL MOISTURE
PROFILES ARE FAVORABLE AND SIMILAR TO YESTERDAYS REVERSE CLOUD LINE
DEVELOPMENT. STEERING FLOWS LATE THIS AFTERNOON AND TONIGHT WILL
TEND TO BE TO THE EAST...SO DO NOT EXPECT MAINLAND CONVECTION TO HAVE
AN INFLUENCE. FOR FRIDAY AND FRIDAY NIGHT...LOW LEVEL MOISTURE
DECREASES AS CONTINENTAL AIR FILTERS ACROSS THE FRACTURED RIDGE AXIS.
STEERING FLOWS ARE A LITTLE MORE FAVORABLE TOMORROW AFTERNOON AND
EVENING FOR MAINLAND CONVECTIVE PROPAGATION...SO HAVE INCLUDED A
SLIGHT CHANCE OF THUNDER FOR ISLAND COMMUNITIES. BY SATURDAY...MAINLY
LIGHT AND VARIABLE WINDS WILL BEGIN A LEGITIMATE VEER TO THE NORTH TO
NORTHEAST AND WILL INCREASE IN RESPONSE TO AN EXPANDING RIDGE IN THE
SOUTHEASTERN UNITED STATES. HEATING ON THE MAINLAND WILL COMPLICATE
THE EXPANSION OF THE RIDGE. AS THE THERMODYNAMICS TAKE ON MORE OF A
CONTINENTAL CHARACTER...LOW LEVEL CONFLUENCE AND CONVERGENCE WILL
INCREASE AS WINDS SURGE FROM THE NORTHEAST. HENCE...COMPETING
VARIABLES WILL MAKE FOR A CHALLENGING FORECAST FOR THE END OF THE
SHORT TERM. WE HAVE ADDED THUNDER TO THE GRIDS SATURDAY
AFTERNOON...AS MAINLAND CONVECTION PROPAGATES TO THE SOUTHWEST.
OTHERWISE...NO OTHER CHANGES.
&&
.LONG TERM (SATURDAY NIGHT THROUGH WEDNESDAY)...THE LONG TERM CAN BE
SUMMED UP WITH ONE WORD...BREEZY. THE CONTINENTAL HIGH WILL SLOWLY MERGE
WITH THE BERMUDA CELL TO ITS EAST. NORTHEAST TO EAST BREEZES WILL
REMAIN TRAPPED UNDERNEATH SIGNIFICANT SUBSIDENCE THROUGH MONDAY.
RAIN CHANCES WILL BE SCANT UNTIL THE SURFACE HIGH SHIFTS
NORTHEAST...WEAKENING THE INVERSION ENOUGH TO ALLOW THE LOW LEVEL
MOISTURE FLUX TO EFFECTIVELY DESTABILIZE THE COLUMN. WE HAVE TRIMMED
POPS AND THUNDER SUNDAY THROUGH MONDAY...AND RETAINED THE POPS
THROUGH THE REMAINDER OF THE LONG TERM. WITH VERY FEW CHANGES TO THE
LOW LEVEL WIND FIELD IN THE LONG TERM...WE HAVE EXTENDED BREEZY
THROUGH DAY 7.
&&
.MARINE...A WEAK PRESSURE PATTERN WILL PREVAIL TODAY THROUGH FRIDAY.
A LARGE AREA OF HIGH PRESSURE WILL BUILD SOUTHWARD DOWN THE FLORIDA
PENINSULA FRIDAY NIGHT AND SATURDAY...RESULTING IN INCREASING
NORTHEAST TO EAST BREEZES. FRESH TO STRONG NORTHEAST TO EAST BREEZES
ARE EXPECTED SATURDAY NIGHT THROUGH MONDAY NIGHT. A SMALL CRAFT
ADVISORY WILL LIKELY BE REQUIRED FOR ALL KEYS COASTAL WATERS SATURDAY
NIGHT THROUGH MONDAY NIGHT. 
&&
.AVIATION...VFR CONDITIONS WILL PREVAIL THROUGH THIS EVENING AT THE
KEY WEST AND MARATHON TERMINALS. THERE IS SOME POTENTIAL FOR A
REVERSE CU LINE TO FORM ALONG THE ISLAND CHAIN DURING THE MID MORNING
THROUGH EARLY AFTERNOON HOURS. DRY AIR ENTRAINMENT ALOFT SHOULD
PREVENT ANY DEEP CONVECTION ALONG THIS LINE...BUT AT LEAST A FEW
SHOWERS WILL BE POSSIBLE. THIS ACTIVITY WOULD PROBABLY REMAIN EAST OF
THE KEY WEST TERMINAL...AND CONFIDENCE IS TOO LOW TO INCLUDE A VCSH
IN MARATHON AT THIS POINT. HAVE INCLUDED A TEMPO FOR MVFR CIGS AT
MARATHON FROM 14Z TO 18Z. LIGHT AND VARIABLE SURFACE WINDS WILL
BECOME NORTHWEST AT 5 TO 8 KNOTS DURING THE AFTERNOON.
&&
.PRELIMINARY POINT TEMPS/POPS...
KEY WEST  88  78  87  78 / 20 10 10 20 
MARATHON  92  78  90  78 / 20 10 10 20 
&&
.KEY WATCHES/WARNINGS/ADVISORIES...
FL...NONE.
GM...NONE.
&&
$$
PUBLIC/MARINE.........CLR
AVIATION/NOWCASTS.....JACOBSON
DATA COLLECTION.......VICKERY
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