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000
FXUS62 KKEY 131949
AFDKEY

AREA FORECAST DISCUSSION FOR THE FLORIDA KEYS
NATIONAL WEATHER SERVICE KEY WEST FL
349 PM EDT THU JUN 13 2013

.DISCUSSION...
CURRENTLY - THE KEYS ARE IN WEAK PRESSURE GRADIENT WITH THE ATLANTIC
RIDGE OFF TO THE EAST...AND A WEAK TROUGH EXTENDING SOUTHWARD INTO
FLORIDA. WINDS HAVE BEEN LIGHT MAINLY OUT OF THE SOUTHEAST. DESPITE
AMPLE INSTABILITY AND MOISTURE...AND LACK OF A CAP...CONVECTIVE
ACTIVITY HAS BEEN RELATIVELY SPARSE TODAY. THIS IS DUE TO THE
UNFAVORABLE LOWER LEVEL FLOW TO FOCUS CONVERGENCE OVER AND NEAR THE
ISLAND CHAIN. MOST SHOWER ACTIVITY HAS BEEN ALONG A MYRIAD OF MARINE
CONVERGENT BOUNDARIES...AND LEE OF THE LARGER LOWER KEYS...AND ONLY A
FEW THUNDERSTORMS HAVE BEEN ABLE TO FORM.

FORECAST - THE LOWER LEVEL FLOW IS EXPECTED TO BACK A BIT LATER THIS
AFTERNOON INTO EVENING...POSSIBLY ALLOWING SOME OF THE LEE SIDE CLOUD
DEVELOPMENT TO STICK CLOSER TO THE KEYS. FURTHER...ANOTHER ROUND OF
SHOWERS AND THUNDERSTORMS ARE LIKELY OVER EXTREME SOUTH FLORIDA.
INTERACTION BETWEEN THESE TWO FEATURES...ALONG WITH THE CURRENTLY
LACKING LOW LEVEL CONFLUENCE SHOULD BE SUFFICIENT TO GENERATE MORE
SHOWER AND THUNDERSTORM ACTIVITY THIS EVENING. WILL MAINTAIN A LOW
CHANCE OF SHOWERS AND THUNDERSTORMS EARLY...DECREASING OVERNIGHT.

THE ZONE OF RELATIVELY FLAT PRESSURE GRADIENT WILL SLIDE
SOUTHWARD OF THE KEYS...RESULTING IN CURRENT SOUTHERLY WINDS
SHIFTING MORE WESTERLY FRIDAY...AND NORTHWEST ON SATURDAY. IN
ADDITION...MUCH DRIER AIR WILL MOVE IN ALOFT ON THE WESTERN PERIPHERY
OF AN UPPER LEVEL TROUGH. MORE STABLE CONDITIONS WILL MOVE IN WITH A
WEAK CAP DEVELOPING BY LATE FRIDAY. CONDITIONS WILL BE RATHER
UNFAVORABLE FOR DEEP CONVECTION DEVELOPMENT FROM FRIDAY THROUGH THE
WEEKEND.

WINDS WILL TRANSITION TO A MORE EASTERLY DIRECTION SATURDAY NIGHT
AND SUNDAY AS A HIGH PRESSURE SYSTEM BUILDS DOWN THE FLORIDA
PENINSULA...AND PRESSURES FALL IN THE WESTERN CARIBBEAN. THE
TIGHTENING OF THE GRADIENT WILL BOOST WINDS A BIT LATE SUNDAY AND
MONDAY...BUT REMAIN BELOW ANY BREEZY WORDING.

GUIDANCE HAS BEEN FAIRLY CONSISTENT IN INDICATING A LOW LEVEL WAVE
RIDING WEST NORTHWESTWARD ALONG THE SOUTHERN PERIPHERY OF THE
ATLANTIC RIDGE...APPROACHING THE ISLAND CHAIN LATE MONDAY INTO EARLY
TUESDAY. INCREASED THETA E ASSOCIATED WITH THIS WAVE...AND A
WEAKENING OF THE CONVECTIVE CAP...SUGGESTS AT LEAST A ROUND OF
SHOWERS AND THUNDERSTORMS IS EXPECTED SOMEWHERE IN THIS TIME FRAME.
FOR NOW WILL MAINTAIN THE ONGOING INCREASE IN POPS TO LOW CHANCE ON
MONDAY.

&&

.MARINE...
LIGHT SOUTHEAST BREEZES WILL SHIFT MORE SOUTHWEST OVERNIGHT AS A WEAK
RIDGE AXIS SLIPS SOUTH OF THE KEYS. WINDS WILL CONTINUE TACKING WEST
THEN NORTHWEST INTO SATURDAY AS THE RIDGE MOVES INTO FLORIDA AND
DISSIPATES. WINDS WILL THEN TRANSITION TO A MORE USUAL EASTERLY FLOW
BY SUNDAY AS ANOTHER HIGH MOVES INTO FLORIDA AND PRESSURES DIP A BIT
IN THE WESTERN CARIBBEAN. OUTSIDE OF A ROUND OF SCATTERED SHOWERS
AND ISOLATED THUNDERSTORMS...CONVECTIVE ACTIVITY IS EXPECTED TO BE
SUPPRESSED THROUGH THE WEEKEND. WINDS ARE EXPECTED
STRENGTHEN...BECOMING GENTLE TO OCCASIONALLY MODERATE LATE SUNDAY
INTO MONDAY AS THE GRADIENT STEEPENS BETWEEN THE RIDGE TO OUR NORTH
AND LOWER PRESSURES IN THE CARIBBEAN. AT THIS TIME...CAUTIONS CAN`T
BE RULED OUT...BUT ARE NOT ANTICIPATED.

&&

.AVIATION...
THROUGH 18Z/13TH...AFTER A LONG DELAY...SHOWERS AND A FEW
THUNDERSTORMS MAY CROSS INTO THE VICINITY OF KEY WEST INTERNATIONAL
OVER THE NEXT FEW HOURS MAINLY TO THE NORTH. LOOKING EVEN LESS
FAVORABLE FOR ANY DIRECT IMPACT TO THE FLORIDA KEYS MARATHON
AIRPORT. OUTSIDE OF THE VARIABLE WINDS NEAR THUNDERSTORMS...THE
LIGHT SOUTHEAST SURFACE WINDS ARE EXPECTED TO BECOME VERY LIGHT
TONIGHT...WITH LIGHT SOUTHWEST TO WEST WINDS EXPECTED BEGINNING
DURING THE LATE MORNING HOURS FRIDAY.

&&

.CLIMATE...
ON THIS DATE IN KEYS WEATHER HISTORY...1900...5.04 INCHES OF RAIN FELL
ON KEY WEST SETTING THE DAILY RECORD FOR RAINFALL ON JUNE 13TH IN
KEY WEST. RAINFALL RECORDS AT KEY WEST DATE BACK TO 1871.

&&

.PRELIMINARY POINT TEMPS/POPS...
KEY WEST  82  89  82  88 / 20 20 10 10
MARATHON  83  93  83  92 / 20 20 10 10

&&

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

$$

PUBLIC/MARINE.........11
AVIATION/NOWCASTS.....RIZZO
DATA COLLECTION.......PARKE

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