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000
FXUS62 KKEY 100247
AFDKEY

AREA FORECAST DISCUSSION FOR THE FLORIDA KEYS
NATIONAL WEATHER SERVICE KEY WEST FL
945 PM EST TUE FEB 9 2010

.DISCUSSION...IN THE MIDDLE AND UPPER LEVELS...700-200 MB...LATEST
AVAILABLE SATELLITE IMAGERY OVERLAID WITH STREAMLINE ANALYSIS AS OF
900 PM DEPICT A DEVELOPING MIDDLE AND UPPER WINTER CYCLONE CENTERED
OVER NORTHERN ILLINOIS AND SOUTHERN WISCONSIN. WELL TO THE SOUTH A
VERY STRONG 125 TO 150 KNOT NEARLY ZONAL JET AT 250 MB IS BLASTING
ACROSS NORTHERN OLD MEXICO...THE GULF OF MEXICO...TO ACROSS NORTH
FLORIDA.

IN THE LOWER TO MIDDLE LEVELS...SURFACE TO 700 MB...LATEST AVAILABLE
SATELLITE IMAGERY OVERLAID WITH MARINE AND LAND SURFACE OBSERVATIONS
AS OF 900 PM DEPICT AN ARCTIC SURFACE HIGH PRESSURE SYSTEM IN
CONTROL CENTERED OVER THE NORTHERN PLAINS. A COMPLEX LOW PRESSURE
SYSTEM WITH CENTERED OVER OHIO AND THE CAROLINAS. A COLD FRONT
EXTENDS FROM THE SOUTHERN LOW SOUTH SOUTHWEST TO 75 TO 100 NM WEST
OF THE DRY TORTUGAS ATTM. AHEAD OF THAT...A PRE-FRONTAL LOW LEVEL
CONFLUENCE HAS RESULTED IN A WIDE BAND OF LIGHT RAINFALL AND SOME
NARROW BANDS OF MODERATE SHOWERS THAT ARE MOVING EAST ACROSS THE
LOWER KEYS AND POINTS WEST ATTM.

.CURRENTLY...AS OF 900 PM...TEMPERATURES RANGE FROM THE UPPER 60S IN
THE LOWER KEYS WHERE THE PREFRONTAL SHOWERS ARE MOVING ACROSS...WITH
LOWER TO MIDDLE 70S STILL IN THE MIDDLE AND UPPER KEYS. KEY WEST
RADAR DETECTS THE AFOREMENTIONED WIDE BAND OF LIGHT RAINFALL WITH A
NARROW BAND OF MODERATE SHOWERS ALONG THE LEADING EDGE OF THE BAND
SITUATED FROM CAPE SABLE SOUTHWEST TO SMITH SHOAL LIGHT...THE
MARQUESAS KEYS THEN SOUTHWEST TO 28 FOOT SHOAL LIGHT.

.SHORT TERM (OVERNIGHT)...IN THE MIDDLE AND UPPER LEVELS...700-200
MB...LARGE SCALE GFS...NAM AND ECMWF ALL INDICATE THE MID AND UPPER
LOW BECOME VERY WELL ALIGNED OVERNIGHT AS IT MIGRATES EASTWARD TO
OFF THE MID ATLANTIC COAST BY LUNCHTIME TOMORROW. AS THIS ENERGY
MOVES AWAY ANY MID AND UPPER ENERGY WILL MOVE EAST OF THE KEYS
OVERNIGHT.

IN THE LOWER AND MIDDLE LEVELS...SURFACE TO 700 MB...OVERNIGHT...AS
THE MAIN LOW DEEPENS OFF OF THE MIDDLE ATLANTIC COAST OVERNIGHT IT
WILL RAPIDLY SWING A COLD FRONT BEHIND THE PREFRONTAL SHOWERS THAT
ARE NOW MOVING ACROSS PORTIONS OF THE MIDDLE AND LOWER KEYS AND
FLORIDA BAY. THE ACTUAL COLD FRONT WILL HAVE MOVED ACROSS THE KEYS
ISLAND CHAIN BETWEEN 1200 AND 200 AM. WINDS WILL CONTINUE TO SHIFT
TO NORTHWEST AND INCREASE TO BETWEEN 15 AND 20 KNOTS JUST AHEAD OF
THE ACTUAL FRONT AS IT SLIDES SOUTHEASTWARD THROUGH THE KEYS THIS
EVENING.

ONLY A QUICK AND NARROW BAND OF MODERATE SHOWERS ARE ASSOCIATED WITH
THE AVAILABLE MOISTURE AND PREFRONTAL SHOWERS. THIS WILL CONTINUE
TO IMPACT FLORIDA BAY AND PORTIONS OF THE LOWER...MIDDLE AND UPPER
KEYS DURING THE NEXT TWO HOURS...WHERE ISOLATED 30 KNOT WIND GUSTS
WILL BE POSSIBLE. BEHIND THAT THE TRAJECTORY OF THE 1000-850 MB COLD
THICKNESS ADVECTION IS SUCH THAT IT WILL CONTINUE TO BE FROM ACROSS
THE GULF TO ACROSS THE KEYS DURING THE OVERNIGHT. HENCE...WIDESPREAD
STRATOCUMULUS WILL OVERSPREAD THE ISLANDS AND ADJOINING WATERS AFTER
MIDNIGHT. THERE IS EVEN THE POSSIBILITY OF SOME LOWER STRATUS COULD
MOVE IN ACROSS THE ISLANDS BETWEEN 1000 PM AND MIDNIGHT. GIVEN
THAT...TEMPERATURES SHOULD ONLY FALL INTO THE LOWER TO MIDDLE 60S
ISLANDWIDE.

WILL ADJUST THE SKY CONDITION WORDING TO REFLECT THAT CHANGE. THOUGH
SOME RAPID DRYING WILL OCCUR ABOVE 800 MB...SOME BRIEF LIGHT RAIN
COULD ACCOMPANY SOME OF THE THICKER STRATOCU OR STRATUS LATER THIS
EVENING AND OVERNIGHT...SO WILL KEEP A SLIGHT CHANCE POP IN THE
GRIDS OVERNIGHT...BUT NO MORE THAN A FEW HUNDREDTHS OF AN INCH COULD
FALL OUT OF THIS TYPE OF PROFILE.


&&

.MARINE...A COLD FRONT WILL PASS THROUGH OUR REGION FROM NORTHWEST
TO SOUTHEAST OVERNIGHT...WITH STRONG NORTHWEST TO NORTH WINDS TO
FOLLOW. SMALL CRAFT ADVISORY IS IN EFFECT ACROSS ALL WATERS FOR
WINDS NEAR 20 KNOTS AND GUSTY.

&&

.AVIATION...THROUGH 10/24Z...COLD FRONT AND SHOWERS WILL CLEAR THE
FLORIDA KEYS BY 09/04Z. THEREAFTER...STRONG NORTHWEST BREEZES WILL
RESULT IN CROSSWINDS OCCASIONALLY EXCEEDING 15KT. MVFR CEILINGS WILL
PREVAIL FOR A SIGNIFICANT FRACTION OF THE TIME THROUGH 10/18Z...WITH
SKIES GRADUALLY CLEARING THEREAFTER.

&&

.KEY WATCHES/WARNINGS/ADVISORIES...
FL...NONE.
GM...SMALL CRAFT ADVISORY FOR ALL KEYS WATERS.

&&

$$

PUBLIC/MARINE/GRIDS..........FUTTERMAN
AVIATION/NOWCASTS............KASPER
DATA ACQUISITION/UPPER AIR...RIZZO

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