Area Forecast Discussion
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000
FXUS62 KKEY 060839 RRA
AFDKEY

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE KEY WEST FL
330 AM EST FRI MAR 6 2015

.DISCUSSION...IN THE MID AND UPPER LEVELS...(700-200 MB)...LATEST
AVAILABLE IR IMAGERY OVERLAID WITH MODEL STREAMLINE ANALYSIS AS OF
200 AM DEPICT A CHANGING PATTERN THAN THE PAST SEVERAL WEEKS...WITH
MUCH LOWER AMPLITUDE RIDGING ACROSS THE CENTRAL AND EASTERN
CONUS...WITH THE EMERGENCE OF A REX BLOCK FEATURE EXTENDING
NORTHEAST INTO CALIFORNIA AND OREGON. 50 TO 75 KNOT SOUTHWESTERLIES
AT 250 MB ARE OBSERVED AT THE BASE OF THE TROUGHING EXTENDING FROM
NORTHERN OLD MEXICO NORTHEASTWARD TO ACROSS THE NORTHERN GULF AND
INTO NORTHERN FLORIDA. SOUTH OF THAT...THERE IS A NARROW YET
BUILDING EAST NORTHEAST TO WEST SOUTHWESTWARD ORIENTED MID AND UPPER
RIDGE THAT HAS SET UP FROM THE NORTHERN BAHAMAS TO THE YUCATAN
PENINSULA...WITH WATER VAPOR IMAGERY DELINEATING MUCH DRIER
SUBSIDENT AIR OVER THE KEYS.

AT THE SURFACE AND IN THE LOWER TO MID LEVELS...SURFACE TO 700
MB...LATEST AVAILABLE IR IMAGERY OVERLAID WITH MARINE AND LAND
SURFACE OBSERVATIONS AND ANALYSIS AS OF 200 AM DETAIL A COLD 1035-
1035 MB SURFACE RIDGE EXTENDING FROM ILLINOIS TO CENTRAL TEXAS. WAY
OUT AHEAD OF THAT FEATURE...A COLD FRONT EXTENDS FROM NORTH CENTRAL
FLORIDA SOUTHWEST TO THE SOUTHWEST GULF OF MEXICO.

.CURRENTLY...AS OF 200 AM...SKIES ARE MOSTLY CLEAR ACROSS THE KEYS
ISLAND CHAIN AND SURROUNDING WATERS. TEMPERATURES OVER THE ISLANDS
ARE IN THE LOWER TO MID 70S WITH DEWPOINTS AROUND 70. WINDS ALONG
THE FLORIDA REEF AND FLORIDA BAY ARE GENERALLY EAST TO SOUTHEAST
NEAR 10 KNOTS...EXCEPT LIGHT AND VARIABLE OUT AT THE DRY TORTUGAS.

.FORECASTS...TODAY THRU TUESDAY NIGHT...A MORE SPRINGLIKE MIDDLE AND
UPPER PATTERN IS INDICATED AS BOTH 00Z ECMWF AND GFS PINCH OFF AN
UPPER LOW NEAR BAJA AS THE REX BLOCK CLOSES OFF TODAY THRU SATURDAY
NIGHT...WITH RESULTANT UPPER AND LOWER JET STREAMS DOWNSTREAM OF
THAT FEATURE CONVERGING TOGETHER OVER THE MID ATLANTIC STATES
SUNDAY. HEIGHT FALLS ARE INDICATED AGAIN OVER THE WEST MONDAY AND
TUESDAY...BUT THE FLORIDA KEYS WILL STILL REMAIN ON THE NORTHERN
PERIPHERY OF THE CARIBBEAN ANTICYCLONE MENTIONED ABOVE IN THE
DISCUSSION...KEEPING LARGE SCALE SUBSIDENT TENDENCIES ABOVE THE
LOWER BOUNDARY LAYER...ABOUT 850 MB.

THE SURFACE COLD FRONT NOW ACROSS NORTH CENTRAL FLORIDA WILL
CONTINUE TO SLIDE SOUTHEASTWARDS...BUT THEN IT HANGS UP OVER SOUTH
FLORIDA SOUTHWESTWARD TO OVER THE SOUTHEASTERN GULF OF MEXICO BY
TONIGHT THROUGH SATURDAY...WITH FRONTOLYSIS ENSUING ALONG THIS
BOUNDARY BY SATURDAY NIGHT. JUST AHEAD OF THE BOUNDARY...EXPECT LOW
LEVEL WINDS TO BACK A BIT TODAY TO BETWEEN NORTH AND NORTHEAST TODAY
AND THIS EVENING ACROSS THE KEYS AND SURROUNDING WATERS. SOME
STRATUS SEEMS LIKE A GOOD POSSIBILITY THIS EVENING ACROSS FLORIDA
BAY AND THE NEARSHORE GULF WATERS NORTH OF THE MIDDLE AND LOWER KEYS
INSIDE THE FIVE FATHOM LINE...GIVEN ADVECTION OF SLIGHTLY COOLER
NEARLY SATURATED AIR MOVING ACROSS THE SKIN OF SLIGHTLY WARMER
SHALLOW WATERS WITH TEMPERATURES IN THE MIDDLE AND UPPER 70S.
THEREFORE...HAVE INDICATED MOSTLY CLOUDY SKIES ACROSS THE KEYS THIS
EVENING. SURFACE WINDS INCREASE AFTER MIDNIGHT ACROSS ALL
WATERS...WITH STRONGER WINDS REMAINING ACROSS THE OFFSHORE GULF
WATERS AND WESTERN STRAITS AFTER MIDNIGHT...CONTINUING WITH THIS
SEPARATION THRU SATURDAY NIGHT.

THE AFOREMENTIONED ARCTIC SURFACE RIDGE NOW NORTH THRU NORTHWEST OF
THE KEYS...STILL REMAINS TO THE NORTH NEAR 1030 MB ACROSS THE
TENNESSEE VALLEY TONIGHT THRU SATURDAY NIGHT...BEFORE IT ELONGATES
INTO THE WESTERN ATLANTIC AND WEAKENS A BIT ON SUNDAY...REMAINING
STATIONARY THROUGH MONDAY NIGHT...AND THEN PULLING EASTWARD INTO THE
WEST CENTRAL ATLANTIC TUESDAY AND TUESDAY NIGHT. GIVEN THE STRONG
SUBSIDENT TENDENCIES IN PLACE BY THE MID AND UPPER CARIBBEAN
ANTICYCLONE...MOISTURE WILL REMAIN BENEATH 850 MB. THEREFORE...GIVEN
MODERATE TO OCCASIONALLY FRESH BREEZES OVER KEYS WATERS GIVEN THE
RELATIVE POSITION OF THE SURFACE ANTICYCLONE...EXPECT ISOLATED
SHOWERS TO DEVELOP ACROSS THE WARMER WATERS THRU THE PERIOD DUE TO
NOCTURNAL/DIURNAL FLUXES...WITH COLUMNAR PWAT REMAINING BETWEEN 1.00
AND 1.25 INCHES. EXPECT HIGH TEMPERATURES WILL REACH THE LOWER 80S
WITH OVERNIGHT LOWS IN THE LOWER TO MID 70S FROM SATURDAY NIGHT
THROUGH TUESDAY NIGHT.

EXTENDED...WEDNESDAY THROUGH THURSDAY...NEAR 590 DM MID LEVEL
RIDGING AT 500 MB SLIDES A BIT MORE EAST...BUT DRY AIR STILL IN
PLACE OVER THE KEYS. VERY STRONG RIDGING OVER THE NORTHEAST WILL
INCREASE THE LOCAL GRADIENT ACROSS THE KEYS AND ADJOINING
WATERS...WITH INDICATIONS OF BREEZY CONDITIONS THRU THESE PERIODS.

&&

.MARINE...LATEST AVAILABLE RUTGERS SST ANALYSIS ACROSS THE
SOUTHEASTERN GULF OF MEXICO AND THE OFFSHORE GULF WATERS 20 TO 60 NM
WEST OF MAINLAND MONROE DOES STILL INDICATE THAT SEA WATERS
TEMPERATURES ARE NEAR 70...SO THIS IS MARGINAL FOR SOME FOG. GIVEN
THE UNCERTAINTY...WILL KEEP IN PATCHY FOG THREAT ACROSS THESE WATERS
FOR THE EVENING HOURS. AFTER MIDNIGHT THE THREAT ENDS AS THE
GRADIENT INCREASES DUE TO THE STRONG COLD RIDGING OVER THE
SOUTHEAST.

GIVEN THE POSITION OF THE STALLING SURFACE FRONT ACROSS THE
SOUTHEAST GULF OF MEXICO LATE TONIGHT THRU SATURDAY NIGHT...THE
STRONGEST WINDS TONIGHT THRU SATURDAY NIGHT WILL BE ACROSS THE
OFFSHORE GULF WATERS AND THE WESTERNMOST FLORIDA STRAITS...WHERE
CAUTIONARY HEADLINES WILL LIKELY BE NEEDED IF NOT SMALL CRAFT
ADVISORIES. THEREFORE I HAVE SPLIT OFF THE WESTERN FLORIDA STRAITS
TO INDICATE HIGHER WINDS AND COMBINED SEAS ACROSS THESE WATERS
TONIGHT THRU SATURDAY NIGHT. CAUTIONARY CONDITIONS ARE NOT
ADVERTISED ACROSS THE REST OF THE MARINE DISTRICT FOR THESE PERIODS
ATTM. CAUTIONARY CONDITIONS WILL BE POSSIBLE FOR SUNDAY THROUGH
MIDWEEK ACROSS HAWK CHANNEL AND ALL FLORIDA STRAITS WATERS...BUT FOR
NOW WE HAVE 15 KNOTS AND GUSTY.
&&

.AVIATION...
VFR CONDITIONS WILL PREVAIL AT EYW AND MTH THROUGH AT LEAST THE NEXT
24 HOURS. SUSTAINED EAST WINDS OF 5 TO 10 KNOTS FROM JUST OFF THE
SURFACE TO ABOUT 3000 FEET WILL BACK TO NORTHEAST AND INCREASE TO 10
TO 15 KNOTS THIS EVENING.

&&

.CLIMATE...
ON THIS DATE IN FLORIDA KEYS WEATHER HISTORY...IN 1987...5.26 INCHES
OF RAIN FELL AT KEY WEST INTERNATIONAL AIRPORT. THIS SET THE DAILY
RECORD FOR MAXIMUM RAINFALL MEASURED IN KEY WEST ON MARCH 6TH. IN
ADDITION...THIS IS THE WETTEST DAY EVER RECORDED IN KEY WEST DURING
THE MONTH OF MARCH. RAINFALL RECORDS AT KEY WEST DATE BACK TO 1871.

&&

.PRELIMINARY POINT TEMPS/POPS...
KEY WEST  82  70  81  73 / -  10 10 10
MARATHON  84  70  83  73 / -  10 10 10

&&

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

$$

PUBLIC/MARINE.........FUTTERMAN
AVIATION/NOWCASTS.....BS

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