Area Forecast Discussion
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FXUS62 KKEY 270852
AFDKEY

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE KEY WEST FL
452 AM EDT WED MAY 27 2015

.DISCUSSION...
A REVIEW OF THE UPPER-LEVEL PATTERN DURING THE LAST 24 HOURS ACROSS
THE REGION INDICATES A SLIGHT WEAKENING AND RE-ORIENTATION OF THE
DEEP LAYER MEAN ANTICYCLONE HAS COMMENCED OVER THE WESTERN NORTH
ATLANTIC. THIS CHANGE HAS ALLOWED A LARGE AREA OF DRY AIR ALOFT TO
OVERSPREAD THE FLORIDA KEYS AND ADJACENT WATERS FROM EAST-NORTHEAST
TO WEST-SOUTHWEST. A SATELLITE-DERIVED SOUNDING FOR A POINT NEAR KEY
WEST AT 300 AM REVEALED A TOTAL PRECIPITABLE WATER VALUE OF 1.30
INCHES...AND DEWPOINT DEPRESSIONS OF 8C AND 22C AT 850MB AND 700MB...
RESPECTIVELY. DESPITE THIS VERY DRY AIR ALOFT...THE WEAKLY SHEARED
DEEP EASTERLY FLOW REGIME HAS ALLOWED ISOLATED CONVECTIVE UPDRAFTS TO
REMAIN ERECT AND SOMEWHAT INSULATED FROM THE RAVAGES OF DRY AIR
ENTRAINMENT. A FEW SHOWERS PASSED THROUGH PORTIONS OF THE LOWER KEYS
AROUND MIDNIGHT DUMPING 0.11 IN BIG COPPITT KEY AND 0.03 HERE AT THE
WEATHER OFFICE IN KEY WEST BY 100 AM. PRESENT DOPPLER RADAR SCANS
SHOW ISOLATED SHOWERS MAINLY OVER THE LOWER STRAITS OF FLORIDA...
MOVING WESTWARD NEAR 20 KNOTS. CURRENT AIR TEMPERATURES IN MOST KEYS
ISLAND COMMUNITIES ARE NEAR 80F...WITH DEWPOINT TEMPERATURES JUST
ABOVE 70F..A DROP OF A FEW DEGREES DURING THE LAST 24 HOURS.

THE FORECAST REASONING HAS NOT CHANGED TOO MUCH DURING THE LAST FEW
CYCLES. THE BREEZY CONDITIONS WILL PERSIST FOR AT LEAST A FEW MORE
DAYS...AND WINDS LIKELY WILL BE SLOW TO COME DOWN DURING THE THURSDAY
NIGHT-SATURDAY TIME FRAME. THE ATMOSPHERE LIKELY WILL REMAIN A BIT
TOO STABLE FOR THUNDERSTORM DEVELOPMENT THROUGH TONIGHT...AND OVERALL
SHOWER COVERAGE SHOULD REMAIN ISOLATED. THIS AFTERNOON MIGHT BE
INTERESTING DOWNWIND OF THE LOWER KEYS AS WEAKLY SHEARED 15-20-KNOT
EAST-NORTHEAST FLOW SHOULD ALLOW A LOWER KEYS STREAMER TO DEVELOP
AND EMANATE WEST-SOUTHWESTWARD OFF THE LOWER KEYS. THIS SETUP HAS THE
POTENTIAL TO SUPPORT A FEW DEEP CONVECTIVE CELLS AND NONSUPERCELL
WATERSPOUTS IN THE KEY WEST-COSGROVE SHOAL REGION. HOWEVER...LOW-
LEVEL DRY AIR ENTRAINMENT MAY BE A LIMITING FACTOR.

RAIN CHANCES GO UP TOWARD EARLY NEXT WEEK AS DEEP RIDGING BREAKS
DOWN AND THE MOIST LAYER DEEPENS.
&&

.MARINE...
A SMALL CRAFT ADVISORY REMAINS IN EFFECT FOR HAWK CHANNEL AND THE
STRAITS OF FLORIDA...AND HAS BEEN EXPANDED TO INCLUDE THE EXTREME
SOUTHEASTERN GULF OF MEXICO. SMALL CRAFT SHOULD EXERCISE CAUTION IN
FLORIDA BAY. AN EXPANSIVE HIGH PRESSURE SYSTEM WILL PERSIST OVER THE
WESTERN NORTH ATLANTIC AND SOUTHEASTERN UNITED STATES TODAY THROUGH
FRIDAY. THIS SETUP WILL MAINTAIN FRESH EAST BREEZES ACROSS FLORIDA
KEYS COASTAL WATERS. BREEZES SHOULD BEGIN TO SLACKEN SOME BY SATURDAY
OR SUNDAY.
&&

.AVIATION...
VFR CONDITIONS WILL PREVAIL AT THE KEY WEST AND MARATHON TERMINALS
TODAY. EAST WINDS WILL CONTINUE BETWEEN 8 TO 15 KNOTS WITH GUSTS UP
TO NEAR 20 KNOTS.
&&

.CLIMATE...
ON THIS DATE IN KEYS WEATHER HISTORY...IN 2000...THE DAILY RECORD
HIGH TEMPERATURE OF 90F WAS LAST OBSERVED AND IN 2009...THE DAILY
RECORD WARM LOW TEMPERATURE OF 81F WAS LAST RECORDED. TEMPERATURE
RECORDS FOR KEY WEST DATE BACK TO 1872.
&&

.PRELIMINARY POINT TEMPS/POPS...
KEY WEST  87  80  87  80 / 10 20 20 20
MARATHON  89  80  90  80 / 10 20 20 20
&&

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

$$

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

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