Area Forecast Discussion
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000
FXUS62 KKEY 201953
AFDKEY

AREA FORECAST DISCUSSION FOR THE FLORIDA KEYS
NATIONAL WEATHER SERVICE KEY WEST FL
253 PM EST SAT DEC 20 2014

.DISCUSSION...THE LOW LEVEL RIDGING HAS RECEDED EAST INTO THE WESTERN
ATLANTIC...GIVING WAY TO LOWERING HEIGHTS WHICH HAVE OVERSPREAD MOST
OF THE UNITED STATES. BROAD-CYCLONIC SURFACE FLOW PREVAILS ACROSS
THE WESTERN CARIBBEAN AND THE GULF OF MEXICO. OBSERVATIONS INDICATE A
WEAK LOW SOUTH OF LOUISIANA...WHILE VISIBLE SATELLITE PHOTOS
HIGHLIGHT A DISTURBANCE NEAR THE YUCATAN PENINSULA...COLLOCATED WITH
A TPW MAXIMUM AND A TRAFFIC JAM IN THE EASTERLIES. CLOSER TO
HOME...GENTLE SOUTHEASTERLY BREEZES HAVE MODERATED TEMPERATURES TO
NEAR 80 DEGREES. DEWPOINTS ARE ON THE RISE AS WELL...ABOUT 8 DEGREES
HIGHER THAN YESTERDAY AT THIS TIME. SKIES HAVE BEEN OCCASIONALLY
VEILED BY THIN LAYERS OF MID-HIGH LEVEL CLOUDS...THE ALTO LAYERS WELL
PORTRAYED BY THE 305 K ISENTROPIC SURFACE. THE RADAR REMAINS ECHO
FREE.

.SHORT TERM (TONIGHT THROUGH MONDAY NIGHT)...NOT MUCH CHANGE IN THE
PATTERN THROUGH THE SHORT TERM...GENTLE EAST-SOUTHEASTERLY
BREEZES...HIGHS NEAR 80...AND LOWS IN THE LOWER 70S. THE WESTERN
EXTENT OF THE LOW LEVEL RIDGE WILL REMAIN DRAPED ACROSS OUR
REGION...SQUELCHING SIGNIFICANT RAIN CHANCES. A WEAK UNDULATION IN
THE STEERING FLOW MAY PASS THROUGH MONDAY...BUT MORE THAN ISOLATED
COVERAGE IS NOT EXPECTED.

&&

.LONG TERM (TUESDAY THROUGH SATURDAY)...THE ACTION BEGINS ON TUESDAY
AS A STRONG MID LATITUDE TROUGH DIGS INTO THE SOUTHERN
PLAINS...PLACING THE GULF OF MEXICO IN AN EXPANSIVE AREA OF
DIFFERENTIAL VORTICITY ADVECTION AND WARM THERMAL ADVECTION. THE
ASSOCIATED BAROCLINIC ZONE WILL STRENGTHEN AS IT DRIVES TO THE
SOUTHEAST ACROSS THE GULF ON TUESDAY NIGHT AND WEDNESDAY. OUR
VERTICAL WIND PROFILE WILL FEATURE STRENGTHENING AND VEERING WINDS
WITH HEIGHT...A SITUATION WHICH NORMALLY INTENSIFIES THE CUBAN
SHADOW. HOWEVER...THE STEERING FLOW WILL VEER JUST ENOUGH TO THE
SOUTHWEST...SOMETIME WEDNESDAY AFTERNOON...IN CONCERT WITH THE COLD
AIR WEDGE APPROACHING FROM THE NORTHWEST. A SHORT PERIOD OF CONFLUENT
AND CYCLONIC FLOW WILL OVERTAKE THE KEYS WEDNESDAY AFTERNOON OR
EVENING...COINCIDENT WITH A MEAGER AMOUNT OF UPPER LEVEL SUPPORT.
STRONG NORTHWEST BREEZES AND COLD AIR ADVECTION WILL FOLLOW A SHARP
NORTHWEST WIND SHIFT...AROUND 00Z THURSDAY. THE RELIABLE GUIDANCE
REMAINS SPLIT WITH TIMING AND THE AMOUNT OF CAA WEDNESDAY NIGHT...SO
OUR FORECAST LEANS ON OUR ONLY AVAILABLE ENSEMBLE SOLUTION. THE
SURFACE HIGH DRIVING THE CONTINENTAL AIR WILL QUICKLY SHIFT EAST
ACROSS FLORIDA...RESULTING IN A QUICK RETURN TO MODERATING
TEMPERATURES.

&&

.MARINE...A WEAK HIGH PRESSURE SYSTEM JUST EAST OF THE FLORIDA
PENINSULA WILL LINGER TONIGHT THROUGH MONDAY. A COLD FRONT WILL
APPROACH THE FLORIDA KEYS TUESDAY AND WILL PASS THROUGH LATE
WEDNESDAY. STRONG NORTHWEST TO NORTH BREEZES WILL FOLLOW A SHARP WIND
SHIFT WEDNESDAY AFTERNOON OR EVENING. MARINERS AND BOATERS SHOULD
PLAN ACCORDINGLY.

&&

.AVIATION...20/18Z TAF ISSUANCE...VFR IS EXPECTED TO PREVAIL AT THE
KEY WEST AND MARATHON AIRPORTS. INCREASING CLOUDS BASED IN THE
FL070-090 LAYER WILL LIKELY BECOME OCCASIONALLY BROKEN COVERAGE
TONIGHT WITH PREDOMINANTLY SCATTERED COVERAGE FL020-025. EAST TO
SOUTHEAST WINDS 6 TO 10 KNOTS WILL CONTINUE THROUGH SUNDAY MORNING.

&&

.CLIMATE...ON THIS DATE IN KEYS WEATHER HISTORY...IN 1973...THE
DAILY RECORD RAINFALL OF 2.50 INCHES WAS RECORDED AT KEY WEST.
RAINFALL RECORDS RECORDS IN KEY WEST DATE BACK TO 1871 AT KEY WEST.

&&

.PRELIM POINT TEMPS/POPS...
KEY WEST  72  79  73  79 / -  -  10 10
MARATHON  72  80  73  80 / -  -  10 10

&&

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

$$

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

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