Area Forecast Discussion
Issued by NWS

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS62 KKEY 290806
AFDKEY

AREA FORECAST DISCUSSION FOR THE FLORIDA KEYS
NATIONAL WEATHER SERVICE KEY WEST FL
300 AM EST MON DEC 29 2014

.DISCUSSION...IN THE MIDDLE AND UPPER LEVELS...(700-200 MB)...LATEST
AVAILABLE IR IMAGERY OVERLAID WITH MODEL STREAMLINE ANALYSIS AS OF
200 AM DEPICT A LARGELY LOW AMPLITUDE CYCLONIC MIDDLE AND UPPER
FLOW PATTERN ENSCONCED ACROSS THE ENTIRE CONUS ON THIS EARLY WINTER
MORNING. THE CENTER OF A DEEP AND WARM ANTICYCLONE IS POSITIONED
OVER THE SOUTHWESTERN CARIBBEAN SEA. AS A RESULT...A APPROXIMATELY
50 TO 75 KNOT SOUTHWESTERLY JET AT 250 MB IS MOVING FROM CENTRAL
AMERICA NORTHEASTERN TO ACROSS SOUTH FLORIDA AND THE KEYS ATTM.

AT THE SURFACE AND IN THE LOWER TO MIDDLE LEVELS...SURFACE TO 700
MB...LATEST IR IMAGERY OVERLAID WITH AVAILABLE MARINE AND LAND
SURFACE OBSERVATIONS AND ANALYSIS AS OF 200 AM DETAIL ONE ARCTIC
COLD FRONT FROM LOWER MICHIGAN TO THE CENTRAL PLAINS. ANOTHER COLD
FRONTAL SYSTEM IS LOCATED FROM THE TIDEWATER SOUTHWEST TO THE WEST
FLORIDA PANHANDLE THENCE SOUTHWARDS TO BISECT THE WESTERN GULF OF
MEXICO. THE WESTERN EDGE OF A 1022 MB SURFACE RIDGE POKES ACROSS
CENTRAL FLORIDA. CONSEQUENTLY THE FLORIDA KEYS ARE BENEATH GENTLE
SOUTHEASTERLIES BENEATH THE SURFACE RIDGE.

.CURRENTLY...AS OF 200 AM...SKIES ARE MOSTLY CLEAR ACROSS THE KEYS
ISLAND CHAIN AND ADJOINING WATERS. TEMPERATURES ACROSS THE ISLANDS
AT THIS HOUR ARE IN THE LOWER TO MID 70S WITH SURFACE DEWPOINTS
AROUND 70 DEGREES. C-MAN STATIONS ALONG THE FLORIDA REEF ARE
RECORDING SOUTHEAST WINDS BETWEEN 8 AND 14 KNOTS AND GUSTY...WITH
FLORIDA BAY AND SMITH SHOAL LIGHT IN THE EXTREME SOUTHEASTERN GULF
OF MEXICO BETWEEN 5 AND 10 KNOTS. A FEW TINY ECHOES HAD APPEARED
EARLIER EAST OF SOUTH FLORIDA BUT NOTHING IS DETECTABLE ATTM.

.FORECASTS...TODAY THROUGH FRIDAY INCLUDING NEW YEARS DAY...A VERY
BENIGN PATTERN IS IN PLACE WITH ABOVE NORMAL TEMPERATURES AND
HUMIDITY VALUES AT THIS TIME OF YEAR THROUGH THE NEXT WEEK AND
WEEKEND ALONG THE ISLAND CHAIN. THE MID AND UPPER PATTERN ACROSS
SOUTH FLORIDA AND THE KEYS WILL CONTINUE TO BE GOVERNED BY 590 DM
PLUS AT 500 MB HEIGHTS REMAINING IN PLACE ACROSS SOUTH
FLORIDA...NORTHERN BAHAMAS...CUBA...AND THE FLORIDA KEYS. ALTHOUGH
THE MID AND UPPER FLOW PATTERN WILL REMAIN LARGELY CYCLONIC THRU THE
PERIOD...AMPLIFICATION IS NOT SIGNIFICANT ENOUGH TO ALLOW FOR ANY
SIGNIFICANT CHANCES IN SURFACE/LOWER LEVELS AIRMASS TEMPERATURES.

AT THE SURFACE...THE WESTERN EDGE OF AN ATLANTIC RIDGE WILL REMAIN
NORTH OF THE KEYS TODAY. WITH WEAK RIDGING REMAINING JUST TO THE
IMMEDIATE NORTH OF THE KEYS THRU TONIGHT...WITH A WEAK TROUGH
APPROACHING TUESDAY AND TUESDAY NIGHT...BACKING THE SURFACE WINDS TO
LIGHT AND GENTLE NORTHEASTERLY ACROSS THE ISLANDS AND ADJOINING
WATERS. THEN THE CENTER OF AM ARCTIC 1030-1035 MB COLD SURFACE HIGH
PRESSURE OVER THE OZARKS ON TUESDAY WILL SLIDE EASTWARD TO THE
SOUTHERN APPALACHIANS AND TENNESSEE VALLEY DURING NEW YEARS DAY AND
FRIDAY...ALLOWING FOR A RESUMPTION IN GENTLE TO MODERATE BREEZES
ACROSS THE KEYS ISLAND CHAIN AND ADJOINING COASTAL WATERS WEDNESDAY
NIGHT THROUGH FRIDAY. VERY LITTLE MOISTURE IN THE BOUNDARY LAYER
WILL KEEP CHANCES FOR MEASURABLE RAINFALL OUT OF THE PICTURE ACROSS
THE ISLANDS FOR TODAY THRU TUESDAY NIGHT...BUT AS THE BOUNDARY LAYER
MOISTENS A TAD TO AROUND 1.25 INCHES PWAT...EXPECT WEAK LOWER LEVEL
CONFLUENT FLOW AHEAD OF AN APPROACHING YET DISINTEGRATING
SURFACE/LOW LEVEL TROUGH OVER THE PENINSULA WEDNESDAY THRU NEW YEARS
DAY...WE CAN EXPECT A SLIGHT CHANCE FOR A VERY BRIEF LATE NIGHT OR
EARLY MORNING SHOWER...PRODUCING NO MORE THAN SEVERAL HUNDREDTHS OF
AN INCH OF RAINFALL.

THE ONLY OTHER ISSUE IS RELATIVE TO A LIGHT TO GENTLE NORTHEASTERLY
MOIST SURFACE TO 850 MB FLOW ACROSS THE KEYS DURING TUESDAY AND
TUESDAY NIGHT. GIVEN HIGHER SURFACE TEMPERATURES AND HUMIDITIES JUST
AHEAD OF THIS APPROACHING SURFACE FRONTAL BOUNDARY TUESDAY AND
TUESDAY NIGHT...THE ADVECTION OF MOIST AIR WITH DEWPOINTS AROUND 70
DEGREES MOVING ACROSS THE SHALLOWER SURFACE WATER TEMPERATURES AT 70
(OR POSSIBLY ONE OR TWO DEGREES COOLER THAN THAT)...USUALLY RESULTS
IN THE DEVELOPMENT OF LOW STRATUS AND/OR AREAS OF FOG UPSTREAM OF
THE KEYS ISLAND CHAIN...WHICH CAN IMPACT THE FLORIDA BAY...THE
IMMEDIATE NEARSHORE GULF WATERS INSIDE THE FIVE FATHOM LINE NORTH OF
THE MIDDLE AND LOWER KEYS...THE GULF WATERS OUTSIDE THE FIVE FATHOM
LINE...THE GULF WATERS 20 TO 60 NM WEST OF MAINLAND MONROE
COUNTY....AND OF COURSE PORTIONS OF THE KEYS ISLAND CHAIN AS WELL.
CONFIDENCE IS NOT HIGH ENOUGH ATTM TO PUT AREAS OF FOG IN THE GRIDS
ATTM BUT HAVE INCLUDED MOSTLY CLOUDY CONDITIONS TUESDAY NIGHT.

FOR WEDNESDAY THRU NEW YEARS DAY...WILL MAINTAIN A DIME POP IN THE
GRIDS ON ACCOUNT OF SLIGHT INCREASED MOISTURE AND LOWER LEVEL
CONFLUENCE ASSOCIATED WITH THE FRONTAL BOUNDARY. DRIER AIR IN THE
MIDDLE LEVELS THURSDAY NIGHT AND FRIDAY WILL TAKE AWAY THE CHANCES
AGAIN FOR MEASURABLE RAIN OVER THE KEYS. TEMPERATURES WILL CONTINUE
TO BE A FEW DEGREES ABOVE BOTH AVERAGE OVERNIGHT LOW AND DAYTIME
HIGH TEMPERATURES ARE IN LATE DECEMBER...WITH HIGHS AROUND 80 AND
LOWS AROUND 70 DEGREES.

THEN ON SATURDAY THRU SUNDAY...WEAK SURFACE RIDGING TO THE IMMEDIATE
NORTH COMBINED WITH VERY DRY AIR IN THE MIDDLE AND UPPER LEVELS WILL
KEEP RAIN CHANCES DOWN IN NEGLIGIBLE TERRITORY. TEMPERATURES WILL BE
ABOVE NORMAL.

&&

.MARINE...WINDS AND SEAS WILL REMAIN BELOW HEADLINE CRITERIA THRU AT
LEAS THURSDAY...WITH LIGHT TO GENTLE WINDS...BECOMING GENTLE TO
MODERATE WEDNESDAY AND THURSDAY. ONE POSSIBLY ISSUE WILL BE AREAS OF
FOG WITH REDUCED VISIBILITY TO FORM ACROSS THE FLORIDA BAY AND THE
SHALLOWER COOLER WATERS INSIDE THE FIVE FATHOM LINE NORTH OF THE
MIDDLE AND LOWER KEYS AS WELL AS THE WATERS 20 TO 60 NM WEST OF
MAINLAND MONROE COUNTY.

THEN A STRONGER HIGH PRESSURE SYSTEM THURSDAY NIGHT THRU THE WEEKEND
COULD RESULT IN A CAUTIONARY HEADLINES FOR THE FLORIDA STRAITS
THURSDAY NIGHT THRU FRIDAY NIGHT...BUT WINDS AND SEAS COULD BE
HIGHER BASED ON THE MAGNITUDE OF THE RIDGING. STAY TUNED.

&&

.AVIATION...SCATTERED CUMULUS AND STRATOCUMULUS MOVING NORTHWESTWARD
ACROSS THE KEYS MAY PRODUCE BRIEF SPELLS OF MVFR CEILINGS BASED
BETWEEN 1800 AND 2200...MAINLY EARLY IN THE MORNING. SURFACE WINDS
WILL BE OUT OF THE EAST SOUTHEAST TO SOUTHEAST AT 5 TO 10 KNOTS.

&&

.CLIMATE...IN 1894...THE HIGH TEMPERATURE IN KEY WEST WAS ONLY 48F
AND THE LOW TEMPERATURE WAS 44F...BOTH RECORDS FOR THE DATE. WITH AN
AVERAGE TEMPERATURE OF 46F...THIS IS THE COLDEST DAY EVER RECORDED
IN KEY WEST. THE 48F READING IS THE COLDEST HIGH TEMPERATURE ON
RECORD, AND THE ONLY OCCASION ON WHICH THE TEMPERATURE HAS FAILED TO
REACH 50F.

&&
.PRELIMINARY POINT TEMPS/POPS...
KEY WEST  81  73  81  71 / -  -  -  -
MARATHON  83  73  83  71 / -  -  -  -

&&

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

$$

PUBLIC/MARINE/CLIMATE/GRIDS......FUTTERMAN
AVIATION/NOWCASTS................11

VISIT US ON THE WEB AT WEATHER.GOV/KEY

FOLLOW US ON FACEBOOK AND TWITTER AT...

WWW.FACEBOOK.COM/NWSKEYWEST
WWW.TWITTER.COM/NWSKEYWEST








USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.