Area Forecast Discussion
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000
FXUS62 KKEY 271859
AFDKEY

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE KEY WEST FL
300 PM EDT FRI MAR 27 2015

.DISCUSSION...IN THE MID AND UPPER LEVELS...(700-200 MB)...LATEST IR
IMAGERY AS OF 200 2M OVERLAID WITH MODEL STREAMLINE ANALYSIS DEPICTS
THE MAIN AXIS OF A DEEP LATE SEASON POLAR TROUGH NOW SITUATED FROM WESTERN
QUEBEC SOUTH SOUTHWEST TO SOUTH CENTRAL GULF OF MEXICO. THE SOUTHEAST
GULF OF MEXICO AND THE FLORIDA KEYS ARE BENEATH THE LOWER RIGHT FLANK
OF THE BASE OF THIS DEEP TROUGH. LOBES OF VORTICITY DO REMAIN JUST TO
THE IMMEDIATE WEST OF THE KEYS AND LINEAR CONVECTION IN THE FORM OF
THUNDERSTORMS HAVE BEEN DEVELOPING IN SITU OVER THESE WATERS. THE MIDDLE
LEVEL DRY AIR HAS BEEN STUBBORN TO ERODE BUT THIS DOES APPEAR TO THE
CASE AS OF THIS HOUR.

AT THE SURFACE AND IN THE LOWER TO MIDDLE LEVELS...(SURFACE TO 700 MB)...
THE LATEST SURFACE ANALYSIS OVERLAID WITH MARINE AND LAND SURFACE ANALYSIS
AND OBSERVATIONS AS OF 200 PM DETAIL THE APPROACHING COLD FRONT EXTENDING
FROM CENTRAL SOUTH CAROLINA SOUTHWEST TO TO BAY OF CAMPHECE. AS JUST
MENTIONED...A LARGE BAND OF LINEAR CONVECTION HAS DEVELOPED FROM JUST
WEST OF MARCO ISLAND SOUTHWEST TO ABOUT 200 MILES DUE WEST OF KEY WEST.
THIS ACTIVITY IS ASSOCIATED WITH A PREFRONTAL TROUGH THAT IS IN PLACE
FROM LAKE OCHEE TO NEAR FT MYERS THENCE TO ABOUT 200 NM WEST OF KEY WEST.

.CURRENTLY...SKIES ARE PARTLY TO MOSTLY CLOUDY ACROSS KEYS WATERS AND ADJOINING
COASTAL WATERS. WIDELY SEPARATED SHOWERS HAVE DEVELOPED ALONG REVERSE CLOUD
LINES WHICH HAVE AFFECTED PORTIONS OF THE UPPER AND MIDDLE FLORIDA KEYS...BUT THIS
ACTIVITY HAS SINCE EVAPORATED WITH ONLY A FEW SHOWERS DOTTING THE STRAITS ATTM.
AT PRESENT...KEY WEST RADAR DETECTS THE LEADING EDGE OF SHOWERS AND
THUNDERSTORMS ABOUT 75 TO 100 NM WEST THRU NORTH OF THE DRY TORTUGAS ATTM.
C-MAN STATIONS ALONG THE FLORIDA REEF ARE REGISTERING SOUTHWEST WINDS
NEAR 15 KNOTS AND GUSTY ALONG THE FLORIDA REEF. SOUTHWEST WINDS NEAR 15 MPH
OVER THE ISLANDS

.FORECASTS...MAIN STORY IS A COLD FRONT WILL IS SLUMBERING EASTWARD ACROSS THE
GULF OF MEXICO ATTM...BUT WILL NOT MOVE ACROSS THE KEYS UNTIL AFTER MIDNIGHT.
UNTIL THEN...SKIES WILL CLOUD UP AND UNLESS AN OUTFLOW PULLS THE AFOREMENTIONED
DOWN ACROSS THE KEYS SOONER...DO NOT SEE THIS IMPACTING THE ISLANDS UNTIL AFTER
8 PM. MAIN THREATS WILL CONTINUE TO BE WIND GUSTS IN EXCESS OF 40 KNOTS...BRIEF
HEAVY RAINFALL ACCOMPANIED BY POOR VISIBILITY...AND OCCASIONAL LIGHTNING.
WINDS WILL INCREASE AND FRESHEN AS THEY VEER TO BETWEEN WEST AND NORTHWEST BY
SUNSET...THEN BECOME STRONG OUT OF THE NORTH BETWEEN 20 AND 25 KNOTS AFTER
MIDNIGHT AFTER FROPA. THE MAGNITUDE OF THE WINDS ARE TRICKIER AT
THIS TIME OF YEAR GIVEN THAT GULF WATERS HAVE WARMED TO NEAR 80
DEGREES...SO THEY CAN BE SEVERAL KNOTS HIGHER THAN THE MODEL
SUGGEST...AS IT IS NOT ALWAYS CAUGHT UP WITH THESE COMPLETE CHANGES
IN THE INITIAL BOUNDARY CONDITIONS.

SO BREEZY CONDITIONS WILL BECOME WINDY OVERNIGHT. SHOWERS WILL
PERSIST FOR A FEW HOURS BEHIND THE FRONT UNTIL VERY DRY AIR IN THE
COOL DEEP CYCLONIC FLOW MOVES SOUTH SOUTHEASTWARD...THEN SOUTHWARD
DOWN THE PENINSULA...SCOURING ANY CHANCE OF CLOUDINESS BY LATE
SATURDAY MORNING. GIVEN THE 1000-850 THICKNESS VALUES...HIGHS WILL
ONLY CLIMB INTO THE LOWER 70S FOR SATURDAY...8 DEGREES BELOW NORMAL.
TEMPERATURES WILL FALL TO NEAR 60 SATURDAY NIGHT...ONLY REBOUNDING
INTO THE MID TO UPPER 70S SUNDAY...THEN RETURNING TO NEAR NORMAL FOR
NEXT WEEK...WITH HIGH TEMPERATURES REACHING NEAR 80 DEGREES THROUGH
MID WEEK AND LOWS IN THE MID 60S SUNDAY NIGHT AND UPPER 60S MONDAY
AND TUESDAY NIGHTS.

EXTENDED...WEDNESDAY THROUGH FRIDAY...WEAKER RIDGING ACROSS THE FLORIDA PENINSULA
WILL BE ACCOMPANIED BY GENTLE TO MODERATE WINDS WITH NEAR NORMAL HIGH TEMPERATURES
REACHING THE LOWER 80S AND LOWS IN THE LOWER 70S. SLIGHTLY HIGHER MOISTURE
IN THE BOUNDARY LAYER SUPPORTS A 10 PERCENT POPS THROUGH THESE PERIODS.

&&

.MARINE...A SMALL CRAFT ADVISORY IS IN EFFECT FOR INCREASING WINDS THROUGH
THIS EVENING. MODERATE TO FRESH WINDS WILL VEER FROM BETWEEN SOUTHWEST AND WEST
TO MAINLY NORTH AND BECOMING STRONG WITH THE FROPA AFTER MIDNIGHT. STRONG
NORTH WINDS WILL CONTINUE THRU LATE SATURDAY MORNING...THEN DIMINISHING A BIT
IN THE AFTERNOON. A SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS IS LIKELY SATURDAY
NIGHT AND SUNDAY FOR THE FLORIDA STRAITS...AND SMALL CRAFT WILL STILL LIKELY NEED
TO EXERCISE CAUTION ACROSS ALL OTHER WATERS IN THE MARINE DISTRICT.


&&

.AVIATION...UNTIL 12Z/28TH...THERE IS A HIGH PROBABILITY OF AT LEAST A FEW MVFR
ENCOUNTERS AT THE KEY WEST AND MARATHON TERMINALS BETWEEN 00Z AND
08Z...WITH VFR CONDITIONS EXPECTED BEHIND A COLD FRONT FOR THE
BALANCE OF THE OVERNIGHT PERIOD. SOUTHWEST WINDS OF 10 TO 15 KNOTS
WITH GUSTS NEAR 20 KNOTS THIS AFTERNOON WILL TURN WEST AT SIMILAR
SPEEDS BY EARL THIS EVENING. WINDS WILL TURN NORTHWEST TO NORTH AND
INCREASE TO NEAR 15 KNOTS WITH GUSTS BETWEEN 22 AND 25 KNOTS BETWEEN
02 AND 05Z. THESE WINDS WILL RESULT IN MODERATE CROSS WINDS FOR THE
BALANCE OF TONIGHT.


&&

.PRELIMINARY POINT TEMPS/POPS...
KEY WEST  70  73  62  75 / 60 0 0 0
MARATHON  69  74  62  76 / 60 0 0 0

&&

.KEY WATCHES/WARNINGS/ADVISORIES...
FL...NONE.
GM...SMALL CRAFT ADVISORY FROM LATE THIS EVENING TO
11 AM EDT SATURDAY FOR GMZ031>035-042>044-052>055-072>075.

&&

$$

PUBLIC/MARINE...................FUTTERMAN
AVIATION/NOWCASTS...............APA
DATA COLLECTION/UPPER AIR.......VICKERY/CHESSER

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