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000
FXUS62 KKEY 112018
AFDKEY

AREA FORECAST DISCUSSION FOR THE FLORIDA KEYS
NATIONAL WEATHER SERVICE KEY WEST FL
315 PM EST WED DEC 11 2013

.DISCUSSION...IN THE MID AND UPPER LEVELS...(700-200 MB)...LATEST
AVAILABLE IR IMAGERY OVERLAID WITH MODEL STREAMLINE ANALYSIS AS OF
200 PM CONTINUES TO DEPICT BROAD LOW AMPLITUDE TROUGHING
ENCOMPASSING MUCH OF THE CONUS FROM THE ROCKIES TO THE EASTERN
SEABOARD. THE SOUTHERN STREAM OF THE 100-150 KNOT UPPER JET AT 250
MB REMAINS WELL NORTH OF THE FLORIDA KEYS...TRAVERSING EAST
NORTHEASTWARD ACROSS THE SOUTHERN CONUS FROM BAJA CALIFORNIA TO LONG
ISLAND. WELL TO THE SOUTH...A CENTER OF THE DEEP AND WARMEST MID
LEVEL RIDGING AT 500 MB CONTINUES TO SHIFT FARTHER TO THE EAST
ACROSS THE CENTRAL ATLANTIC...AND IS WELL NORTHEAST OF THE NORTHERN
WINDWARD ISLANDS...BUT ANOTHER DOMINANT MID LEVEL RIDGE AT 500 MB IS
ASSUMING CONTROL OVER SOUTH FLORIDA FROM THE WESTERN CARIBBEAN.

AT THE SURFACE AND IN THE LOWER TO MID LEVELS...SURFACE TO 700
MB...LATEST IR IMAGERY OVERLAID WITH LATEST AVAILABLE MARINE AND
LAND SURFACE OBSERVATIONS AND ANALYSES AS OF 200 PM DETAIL THE
CENTER OF THE STRONGEST 1040-1045 SURFACE RIDGING OF ARCTIC ORIGINS
REMAINS POSITIONED FROM THE WASATCH RANGE TO THE CENTRAL PLAINS.
WELL SOUTHEAST OF THAT FEATURE...A SURFACE COLD FRONT EXTENDS FROM
THE NORTHWESTERN ATLANTIC SOUTHWEST TO ACROSS CENTRAL FLORIDA NEAR
LAKE OKECHOBBE. THE BOUNDARY IS NEARLY STATIONARY ACROSS THE
PENINSULA.

.CURRENTLY...AS OF 200 PM...LATEST IR IMAGERY AND RADAR SCANS
CONTINUE TO DETECT PARTLY TO MOSTLY CLOUDY SKIES ACROSS THE ISLANDS
AND SURROUNDING WATERS...WITH GOOD COVERAGE OF SCATTERED SHOWERS
WITH THE POSSIBILITY OF A FEW THUNDERSTORMS ACROSS THE FLORIDA
STRAITS OUT 60 NM FROM SOMBRERO KEY LIGHT WESTWARD TO DRY TORTUGAS
LIGHT. ACROSS THE ISLANDS...SCATTERED SHOWERS ARE IMPACTING THE
ISLANDS FROM LONG KEY TO LITTLE PALM ISLAND. OUTSIDE OF SHOWERS...IT
IS A WARM AND HUMID AFTERNOON FOR MID DECEMBER ACROSS THE FLORIDA
KEYS WITH TEMPERATURES NEAR 80 DEGREES AND DEWPOINTS IN THE LOWER TO
MID 70S. THE FEW AVAILABLE C-MAN STATIONS ALONG THE FLORIDA REEF ARE
REGISTERING EAST WINDS AT 10 TO 15 KNOTS. WINDS HAVE GUSTED TO 25
KNOTS IN HEAVIER SHOWERS.

.SHORT TERM (TONIGHT THRU FRIDAY NIGHT )...ELEVATED CHANCES FOR
SHOWERS WILL CONTINUE THROUGH THE OVERNIGHT HOURS AND THE FIRST HALF
OF THURSDAY...GIVEN THE COMBINATION OF DEEPER WELL ABOVE NORMAL
MOISTURE IN THE LOWER TO MID LEVELS...WITH BOTH LATEST AVAILABLE
ECMWF AND GFS MODEL FORECAST SOUNDINGS ILLUSTRATING
PWAT(PRECIPITABLE WATER) BETWEEN 1.75 AND 2.00 INCHES THRU
12Z...COUPLED WITH LOW LEVEL CONVERGENCE WELL AHEAD OF THE
AFOREMENTIONED FRONTAL BOUNDARY NEAR LAKE OKECHOBBE.
THEREAFTER...THE 1040 MB ARCTIC RIDGING NOW OVER THE PLAINS WILL
MOVE INTO THE MID MISSISSIPPI VALLEY ON THURSDAY AFTERNOON...FINALLY
PUSHING THE SURFACE BOUNDARY THROUGH THE KEYS BY THURSDAY EVENING.
NORTHEAST WINDS WILL FRESHEN ACCORDINGLY AS HIGH PRESSURE ONCE AGAIN
BRIDGES IN FROM THE NORTH...BUT ONCE AGAIN THE ONLY CHANGES WILL BE
ISODROSOTHERMAL IN NATURE...(CHANGE IN SURFACE DEWPOINTS FROM THE
LOWER TO MID 70S DOWN TO THE MID 60S).

THEN THE STRONG ARCTIC SURFACE RIDGING WILL MIGRATE QUICKLY TO THE
CAROLINA COAST BY FRIDAY NIGHT...AS MIDDLE LEVEL HEIGHT RISES
CONTINUE OVER THE KEYS IN ASSOCIATION WITH A BUILDING MID LEVEL
ANTICYCLONE OVER THE WESTERN CARRIBEAN. THE RESULT WILL BE MOSTLY
CLEAR SKIES ACROSS THE ISLANDS AND SURROUNDING WATERS...HOWEVER...
AN DESPITE THE MIDDLE LEVEL DRIER AIR BUILDING IN...STRONG SURFACE
TO 850 MB...LOW LEVEL CONVERGENCE/AIR SEA FLUXES WILL STILL RESULT
IN ISOLATED SHOWERS THURSDAY NIGHT THROUGH FRIDAY NIGHT. BOTH HIGH
AND LOW TEMPERATURES WILL CONTINUE TO BE SEVERAL DEGREES ABOVE
NORMAL.

EXTENDED...SATURDAY THROUGH WEDNESDAY...MODELS ARE MORE CONSISTENT
WITH A STRONG PIECE OF MIDLEVEL ENERGY COMING OUT OF THE SOUTHWEST
AND THEN PHASING UP WITH THE NORTHERN STREAM AGAIN OVER THE PLAINS
ON SATURDAY...WITH AMPLIFICATION OF THE TROUGH ACROSS THE CENTRAL
AND EASTERN CONUS ON SUNDAY AND SUNDAY NIGHT...BUT THE LARGE SCALE
SYNOPTIC SCALE TROUGH WILL STILL BE OF LOWER AMPLITUDE ACROSS THE
CENTRAL AND EASTERN CONUS...WITH KEYS WEATHER PRIMARILY DICTATED BY
THE AFOREMENTIONED DEEPER MID-LEVEL ANTICYCLONE REMAINING OVER
CUBA...THE FLORIDA STRAITS AND THE KEYS. THUS...GENTLE TO MODERATE
WINDS ON SATURDAY WILL BECOME LIGHT ACROSS THE KEYS AGAIN SUNDAY AND
MONDAY...AS THE NEXT COLD FRONT IS PROGGED TO GET HUNG UP OVER THE
FLORIDA PENINSULA JUST NORTH OF THE KEYS MONDAY AND TUESDAY...WITH
HIGH PRESSURE ONCE AGAIN BRIDGING ACROSS THE FRONT ON WEDNESDAY.
TEMPERATURES REMAIN ABOVE NORMAL.

&&

.MARINE...NO HEADLINES OR ADVISORIES EXPECTED THROUGH TONIGHT. A
SMALL CRAFT ADVISORY WILL LIKELY BE REQUIRED ACROSS THE OFFSHORE
GULF WATERS 20 TO 60 NM WEST OF MAINLAND MONROE BY THURSDAY
AFTERNOON...AND ACROSS ALL WATERS IN THE KEY WEST MARINE DISTRICT
THURSDAY NIGHT THROUGH FRIDAY. SMALL CRAFT WILL LIKELY STILL NEED
TO EXERCISE CAUTION ACROSS ALL WATERS FRIDAY NIGHT...AND HEADLINES
OR ADVISORIES ARE NOT EXPECTED SATURDAY NIGHT THRU MONDAY NIGHT.

&&

.AVIATION...UNTIL 12Z/12TH...SEVERAL MVFR ENCOUNTERS ARE LIKELY AT
THE KEY WEST AND MARATHON TERMINALS...WILL THE BEST CHANCE OF THESE
SUB-VFR EPISODES LIKELY THIS AFTERNOON AND AGAIN AFTER MIDNIGHT.
AWAY FROM SHOWERS...MOSTLY EAST WINDS OF 10 KNOTS WITH GUSTS NEAR 15
KNOTS ARE ANTICIPATED AT ISLAND AIRPORTS.

&&

.PRELIMINARY POINT TEMPS/POPS...
KEY WEST  74  80  72  80  74 / 40  30  10  10  10
MARATHON  74  81  73  81  75 / 40  30  10  10  10

&&

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

$$

PUBLIC/MARINE/GRIDS..................FUTTERMAN
AVIATION/CLIMATE/NOWCASTS............APA
UPPER AIR/DATA ACQUISITION...........PARKE/LKASPER


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