Area Forecast Discussion
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000
FXUS62 KKEY 061352
AFDKEY

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE KEY WEST FL
1000 AM EDT WED MAY 6 2015

.DISCUSSION...IN THE MID AND UPPER LEVELS...(700-200 MB)...LATEST
AVAILABLE IR IMAGERY AS OF 900 AM OVERLAID WITH MODEL STREAMLINE
ANALYSIS DETAILS THE MAIN AXIS OF A MID AND UPPER TROUGH FROM 500-
200 MB SITUATED FROM A NEARLY CUTOFF LOW PRESSURE SYSTEM OVER THE
MID MISSISSIPPI VALLEY SOUTH SOUTHEASTWARD TO THE FLORIDA
PENINSULA...BUT NEARLY 40 KNOT WINDS AT 250 MB ROUND THE BASE OF THE
TROUGH ACROSS CUBA...THEN STREAM NORTHWARD TO EAST OF FLORIDA AND
THE CAROLINAS...HOWEVER...MUCH LIGHTER WINDS ARE NOTED FROM 700 UP
TO 500 MB...IN THE MID LEVELS EAST OF NORTH FLORIDA BENEATH
SOME DIFFLUENCE AT 250 MB AT THIS LOCATION.

AT THE SURFACE AND IN THE LOWER TO MIDDLE LEVELS...SURFACE TO 700
MB...AS OF 900 AM...SURFACE TO 700 MB LOW PRESSURE...JUST NORTH OF
GRAND BAHAMA ISLAND...IS BECOMING BETTER DEFINED NEAR 30 NORTH AND
77 DEGREES WEST. THE NATIONAL HURRICANE CENTER IS MONITORING THIS
LOWER PRESSURE AREA FOR POSSIBLE TROPICAL OR SUBTROPICAL DEVELOPMENT
BY THURSDAY FOR FRIDAY. THE FLORIDA KEYS ARE NOW IN A COL ZONE
BETWEEN THE DEVELOPING LOW PRESSURE EAST OF FLORIDA...AND RIDGING
OVER THE GULF OF MEXICO.

.CURRENTLY...AS OF 900 AM...SKIES ARE MOSTLY SUNNY ACROSS THE KEYS
AND ADJOINING WATER...WITH LATEST RADAR AND VISIBLE SATELLITE
IMAGERY ONLY DEPICTING A NARROW BAND OF LOW TOPPED SHOWERS IN THE
OUTER STRAITS. TEMPERATURES ACROSS THE ISLANDS ARE IN THE MIDDLE TO
UPPER 70S WITH DEWPOINTS AROUND 70. C-MAN STATIONS ALONG THE FLORIDA
REEF...SOUTHERN FLORIDA BAY...AND SMITH SHOAL LIGHT ARE NORTH TO
NORTHEAST BETWEEN 5 AND 10 KNOTS. THE 12Z SOUNDING ILLUSTRATED LIGHT
TO GENTLE NORTH TO NORTHEAST WINDS UP TO 700 MB....THEN BECOMING
WESTERLY ABOVE THAT...BUT NOT BECOMING STRONG UNTIL ABOVE 400 MB.
NEVERTHELESS...THE LOWER TO MID TROPOSPHERE WAS RATHER DRY WITH
COLUMNAR PWAT(PRECIPITABLE WATER) AT 1.36 INCHES.

.SHORT TERM...LATEST AVAILABLE GFS AND ECMWF MODEL FORECAST
SOUNDINGS ILLUSTRATE A FAVORABLE WIND ORIENTATION FOR ISLAND
CLOUDLINES GIVEN THE WIND PROFILE FROM THE SURFACE TO 700 MB...BUT
WINDS ABOVE 700 MB...OR THE AVERAGE 0-6 KM WOULD ONLY FAVOR MAINLAND
CONVECTION TO REACH THE FLORIDA BAY AND THE UPPER KEYS. THE FIRST
PROBLEM IS THAT THE WINDS AT THIS OUR ARE BECOMING MORE FAVORABLE
RATHER THAN NORTHEASTERLY. ADDITONALLY...MODEL FORECAST SOUNDINGS
ARE ILLUSTRATING ADDITONALLY MID-LEVEL DRY AIR SEEPING IN WHICH IS
GENERALY PROHIBITIVE TO CLOUD LINE FORMATION. LARGE SCALE LIFT IS
SOMEWHAT ELEVATED ACROSS THE AREA GIVEN THE DISORGANIZED LOW
PRESSURE SYSTEM POSITIONED EAST OF FLORIDA...HOWEVER...IF THIS
SYSTEM DOES GET BETTER ORGANIZED THRU THE COURSE OF THE
DAY...ADDFITONAL SUBSIDENT TENDENCIES WOULD BE INTRODUCED ACROSS
THE KEYS WHICH ARE ON THE PERIPHERY SYNOPTICALLY. A MORNING UPDATE
LOOKS LIKELY IF THESE TRENDS CONTINUE TO LOWER RAIN CHANCES TO
ISOLATED...WITH ONLY SOME LIGHT SHOWERS...WHICH WOULD BE MORE LIKELY
TO OCCUR OVER THE UPPER KEYS.

&&

.MARINE...NO ADVISORIES AND NO HEADLINES. AN AREA OF LOW PRESSURE
ACROSS THE NORTHERN BAHAMAS WILL MOVE NORTHWARD TODAY THROUGH
THURSDAY. THEREAFTER...AN ATLANTIC RIDGE WILL BUILD SLOWLY ACROSS
SOUTHERN FLORIDA THURSDAY NIGHT THROUGH SUNDAY.

&&

.AVIATION...
VFR WILL PREVAIL AT THE EYW AND MTH TERMINALS THROUGH THIS EVENING.
EXPECT VARIABLE WINDS TO DEVELOP AT BOTH TERMINALS. RAIN CHANCES
WILL LIMITED TO A SHORT WINDOW EARLY THIS AFTERNOON...FOLLOWED BY
MAINLY DRY CONDITIONS AT BOTH TERMINALS.

&&

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

&&

$$

PUBLIC/MARINE.........DAF
AVIATION/NOWCASTS.....CLR
DATA COLLECTION.......CHESSER

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