FXUS62 KTAE 260732
AFDTAE
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TALLAHASSEE FL
232 AM EST SAT DEC 26 2009
.SYNOPSIS...03 UTC SURFACE ANALYSIS SHOWS A 1008 MB LOW ACROSS
EASTERN CAROLINA WITH A COLD FRONT EXTENDING SOUTHWARD ACROSS THE
WESTERN ATLANTIC AND EASTERN FLORIDA. THIS FRONT PASSED THROUGH OUR
REGION ON FRIDAY MORNING. WELL BEHIND THIS SYSTEM IS THE MAIN
OCCLUDED STORM SYSTEM ACROSS THE UPPER PLAINS WITH A 993 MB SURFACE
LOW CENTERED OVER CENTRAL IOWA. THE SECONDARY COLD FRONT ASSOCIATED
WITH THIS STORM SYSTEM IS MOVING INTO OUR REGION AND REPRESENTS THE
LEADING EDGE OF THE MUCH COOLER AND DRIER AIRMASS THAT WILL STAY IN
PLACE ACROSS THE REGION FOR THE NEXT FEW DAYS.
UPPER AIR DATA AT 500 MB IS QUITE INTERESTING WITH A 520 DM LOW
CENTERED OVER NORTHERN MISSOURI. CLOSED ISOHEIGTS ON THE 500 MB
SURFACE EXTEND WEST TO EAST FROM THE GREAT SALT LAKE TO CLEVELAND
OHIO. SHORT WAVE RIDGING IS IN PLACE ON THE WESTERN AND EASTERN
EDGES OF THIS UPPER LOW.
&&
.SHORT TERM...(TODAY THROUGH MONDAY).
AFTER THE LAST COUPLE OF DAYS OF ACTIVE WEATHER...THE SHORT TERM
PERIOD LOOKS TO BE MAINLY QUIET...BUT QUITE COOL. IN FACT...MANY
LOCATIONS WILL STRUGGLE TO GET MAX TEMPS OUT OF THE 50S.
TODAY...MAINLY A TEMPERATURE FORECAST HERE AS DRIER AIR WILL MOVE IN
QUICKLY BEHIND THE SECONDARY COLD FRONT THAT IS NOW MOVING THROUGH
THE EASTERN PORTIONS OF THE REGION. EVEN THOUGH THE COLD FRONT IS
PUSHING THROUGH...CONTINUED SOUTHWESTERLY FLOW ALOFT IS ALREADY
BRINGING IN A RATHER THICK CIRRUS LAYER. BOTH THE NAM AND GFS SHOW
THIS CLOUD LAYER THICKENING AND LOWERING BY AFTERNOON. THIS WILL
ALSO LIMIT TEMPERATURES AND SHOULD RESULT IN LOW TO MID 50S FOR
HIGHS AREA WIDE TODAY. THE WINDS WILL BE LIGHTER TODAY WITH WEAK
SURFACE HIGH PRESSURE BUILDING IN FROM THE WEST...SO IT SHOULDN'T
FEEL TOO COOL.
TONIGHT...AS THE LARGE UPPER LOW BEGINS TO MOVE NORTHEASTWARD INTO
THE UPPER GREAT LAKES...A PIECE OF ENERGY AROUND THE SOUTHWESTERN
SIDE OF THE LOW WILL DRIVE TOWARD THE GULF COAST. AS THIS ENERGY
NEARS THE NORTHWESTERN GULF...A WEAK SURFACE LOW IS PROGGED TO
DEVELOP AND BEGIN MOVING EASTWARD. THIS LOW SHOULD TRACK WELL SOUTH
OF OUR WATERS TONIGHT AND ON SUNDAY. HOWEVER...THERE LOOKS TO BE
ENOUGH MOISTENING AND FORCING IN THE MID LEVELS TO LEAD TO A FEW
VERY LIGHT SHOWERS ALONG THE PANHANDLE AND BIG BEND COASTS. FURTHER
INLAND...ESPECIALLY INTO ALABAMA AND GEORGIA...IT SHOULD BE TOO DRY
IN THE LOW LEVELS TO SUPPORT PRECIPITATION. IN FACT...THIS MAY BE
THE CASE ALONG THE FLORIDA COAST TOO AS THE PRECIPITATION WILL BE
INITIATING AROUND 750 MB AND HAVING TO FALL THROUGH A VERY DRY
LAYER. CHECKED BRIEFLY THE WINTER PROGS FOR NON-LIQUID PRECIPITATION
GIVEN DEWPOINTS IN THE UPPER 20S AND SURFACE TEMPS IN THE MID 30S.
HOWEVER...PARTIAL THICKNESSES (1000-850 MB AND 850-700 MB) ARE NOT
SUPPORTIVE OF ANY FROZEN PRECIPITATION. MOREOVER...PRECIP INITIATION
LEVEL ON THE SOUNDINGS IS RIGHT AROUND THE FREEZING LEVEL...MEANING
WE WOULD LIKELY BE DEALING WITH LIQUID PRECIP RIGHT FROM THE START
ANYWAY.
SUNDAY AND SUNDAY NIGHT...AS THE SURFACE LOW MOVES SOUTH OF THE
FORECAST AREA...CLOUD COVER WILL CONTINUE TO LIMIT AFTERNOON WARMING
AND HOLD TEMPERATURES INTO THE MID TO UPPER 50S. SKIES WILL BEGIN TO
SLOWLY CLEAR SUNDAY NIGHT AS A DRY FRONTAL BOUNDARY MOVES INTO THE
AREA FROM THE NORTHWEST.
MONDAY...WEAK MID LEVEL RIDGING AND SURFACE RIDGING OFF TO THE WEST
WILL RESULT IN A MOSTLY SUNNY...BUT COOL DAY UNDER DRY NORTHWEST
FLOW. TEMPERATURES...EVEN UNDER FULL SUNSHINE WILL ONLY WARM INTO
THE MID TO UPPER 50S. HOWEVER...THE MOSTLY SUNNY WEATHER WILL NOT
LAST LONG AS ANOTHER STORM SYSTEM WILL BE RAPIDLY TAKING SHAPE TO
OUR WEST MONDAY NIGHT.
.LONG TERM...(MONDAY NIGHT THROUGH SATURDAY).
THE PERIOD WILL BEGIN WITH THE POTENTIAL FOR A LIGHT FREEZE OVER
PARTS OF THE REGION LATE MONDAY NIGHT AND TUESDAY MORNING...BUT
THERE IS STILL PLENTY TO QUESTION IN THE NAM...GFS...AND ECMWF...IF
THE COLD SFC RIDGE WILL BE IN A FAVORABLE ENOUGH POSITION TO ALLOW
FOR ENOUGH RADIATIONAL COOLING TO SUPPORT IT. DESPITE THE AVAILABLE
NUMERICAL GUIDANCE INDICATING A FAIRLY WIDESPREAD LIGHT FREEZE
(NAMELY THE MEX AND MOS GUIDANCE)...THE RAW GFS40 SFC DATA MAY HAVE
A BETTER HANDLE ON THE SITUATION SHOWING LOWS GENERALLY IN THE LOWER
TO MID 30S...WHICH DEFINITELY FITS THE SYNOPTIC PATTERN WITH THE
CENTER OF THE SFC HIGH WELL TO OUR NW. THIS SITUATION WOULD LIKELY
KEEP SFC WINDS AT LEAST 3-5 MPH THROUGHOUT MUCH OF THE NIGHT...WHICH
IS USUALLY PLENTY STRONG ENOUGH TO PREVENT A RADIATIONAL COOLING
LIGHT FREEZE. THEREFORE...AM PLANNING ON BUMPING UP OUR CURRENT LOWS
A BIT...WHICH WILL STILL SHOW SOME BELOW FREEZING TEMPERATURES...BUT
NOT COLD ENOUGH OR WITH LONG ENOUGH DURATIONS FOR A TRUE LIGHT
FREEZE. THEN...OUR ACTIVE EL NINO PATTERN WILL GET BACK INTO ACTION
WITH YET ANOTHER GULF LOW POTENTIALLY ON OUR DOORSTEP AS EARLY AS
WEDNESDAY MORNING...JUST IN TIME TO CLOSE OUT THE 2009 CALENDAR YEAR
WITH A HEALTHY BATCH OF RAIN LASTING INTO AT LEAST THURSDAY MORNING.
THE 12 UTC RUN OF THE ECMWF IS A BIT SLOWER...AND WOULD ALSO DEVELOP
ANOTHER SFC WAVE AND LINGER THE RAINFALL INTO THE FIRST HALF OF
FRIDAY...SO IT WILL BE INTERESTING TO SEE HOW THE NEW 00 UTC EURO
RUN TRENDS. ALSO...UNLESS THERE ARE MAJOR CHANGES DOWN THE LINE
EXPECT THE CWA TO GENERALLY REMAIN IN THE COOL SECTOR WITH THIS
EVENT...SO THE SVR WX POTENTIAL DOES NOT APPEAR TO BE AN ISSUE AT
THIS TIME. DESPITE ALL OF THE ABOVE INTERESTING WEATHER...PERHAPS
THE MOST INTERESTING PORTION OF THE FCST WILL COME AT THE VERY END
OF THE PERIOD AND WILL BE FURTHER DISCUSSED IN THE EXTENDED
DISCUSSION TOMORROW NIGHT...AS INDICATIONS ARE POINTING TO THE
POTENTIAL FOR AN EXTREMELY COLD AIR MASS TO HEAD OUR WAY BEHIND THIS
LOW FOR NEXT SATURDAY AND SUNDAY. THIS COULD VERY WELL LEAD TO OUR
FIRST HARD FREEZE OF THE SEASON.
&&
.AVIATION... THERE IS STILL ONE SMALL BATCH OF MVFR LEVEL CIGS WHICH
IS AFFECTING OUR EASTERN GA COUNTIES VERY EARLY THIS MORNING...WITH
THE VLD TERMINAL POSSIBLY REMAINING UNDER MVFR FLIGHT RULES UNTIL
ABOUT 08 OR 09 UTC. THEREAFTER...BKN CIRRUS AT 25K FT SHOULD SHOULD
REPLACE THESE LOWER CIGS...AS HAS ALREADY TAKEN PLACE AT OUR
REMAINING TAF SITES. DESPITE THE INCREASING HIGH AND THEN MID LEVEL
CLOUDINESS FROM WEST TO EAST TONIGHT THROUGH SAT EVENING AS A WEAK
SFC LOW DEVELOPS OFF TO OUR SOUTH...EXPECT VFR FLIGHT RULES TO HOLD
THROUGH THE PERIOD...WITH ANY MORE PESSIMISTIC CONDITIONS HOLDING
OFF UNTIL SUNDAY IF SOME LIGHT RAIN BEGINS TO BREAK OUT.
&&
.MARINE...SMALL CRAFT ADVISORY CONDITIONS CONTINUE OVER THE OFFSHORE
LEGS THIS MORNING DUE TO SEAS GREATER THAN 7 FEET. NEAR SHORE LEGS
HAVE DROPPED BELOW 7 FEET...SO WILL DISCONTINUE THE ADVISORY THERE
ON THE MORNING PACKAGE. I AM CONTEMPLATING EXTENDING THE SCA FOR THE
OFFSHORE LEGS UNTIL 15Z SINCE IT WILL TAKE A LITTLE MORE TIME FOR
THE OFFSHORE LEGS TO DROP BELOW CRITERIA. THIS DECISION WILL BE MADE
BASED ON THE 3 AM AND 4 AM OBS...BUT THE SCA WILL LIKELY NEED TO BE
EXTENDED. AFTER THIS MORNING...NO ADDITIONAL HEADLINE CRITERIA IS
EXPECTED UNTIL MONDAY MORNING WHEN OFFSHORE WINDS MAY REACH 15 TO 20
KNOTS IN OFFSHORE FLOW...BUT THIS WILL BE RELATIVELY SHORT LIVED
WITH LIGHTER WINDS EXPECTED ON TUESDAY. ANOTHER GULF LOW ON
WEDNESDAY WILL RAPIDLY RAMP UP WINDS AND SEAS TO SCA LEVELS THOUGH
THE EXACT STRENGTH AND TRACK OF THE LOW WILL DETERMINE IF GALE
CRITERIA COULD BE MET ON WEDNESDAY NIGHT AND THURSDAY.
&&
.FIRE WEATHER...LATEST FORECAST SHOWS AROUND 3 HOURS OF LOW RH TODAY
IN NORTH FLORIDA. THIS IS PRIMARILY BASED ON SLIGHTLY COOLER
TEMPERATURES DUE TO ADVANCING CLOUD COVER. THUS...WILL CANCEL THE
FIRE WEATHER WATCH BUT INCLUDE A STATEMENT ABOUT THE POTENTIAL FOR 3
HOUR DURATIONS. NO FIRE WEATHER CONCERNS ARE EXPECTED AGAIN UNTIL
TUESDAY WHEN A MUCH DRIER AIRMASS WILL BE IN PLACE.
&&
.PRELIMINARY POINT TEMPS/POPS...
TALLAHASSEE 55 35 59 37 58 / 0 10 10 5 0
PANAMA CITY 55 39 60 41 56 / 0 20 10 0 0
DOTHAN 54 33 59 36 54 / 0 10 0 0 0
ALBANY 54 33 59 35 55 / 0 0 0 0 0
VALDOSTA 56 34 59 37 57 / 0 0 10 5 0
CROSS CITY 58 34 62 38 61 / 0 10 20 10 0
APALACHICOLA 54 38 59 40 57 / 0 20 20 5 0
&&
.TAE WATCHES/WARNINGS/ADVISORIES...
AL...NONE.
GA...NONE.
FL...NONE.
GM...SMALL CRAFT ADVISORY UNTIL 10 AM EST THIS MORNING FROM DESTIN
TO THE SUWANNEE RIVER ENTRANCE BETWEEN 20 AND 60 NAUTICAL MILES
FROM SHORE.
&&
$$
AVIATION/LONG TERM...GOULD
REST OF DISCUSSION...GODSEY
