FXUS62 KTAE 110734
AFDTAE
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TALLAHASSEE FL
234 AM EST FRI DEC 11 2009
.SYNOPSIS...THE SPLIT FLOW REGIME CONTINUES OVER THE ERN PAC AND WRN
N AMERICA THIS MORNING WITH CONFLUENT FLOW DOWNSTREAM OVER THE ERN
U.S. WHERE WE SEE A 175-KT UPPER JET OVER THE TN/KY REGION. SURFACE
ANALYSIS SHOWS COLD HIGH PRESSURE CENTERED OVER THE LOWER MS AND TN
VALLEYS. THE COLD FRONT THAT SEEMED TO TAKE FOREVER TO CROSS OUR
FORECAST AREA HAS SINCE ZIPPED DOWN THE PENINSULA AND IS NOW
APPROACHING THE KEYS. AN AREA OF LOW PRESSURE IS DRIFTING NWD ON THE
WRN END OF THIS FRONT OVER THE SWRN GULF OF MEXICO. A TIGHT GRADIENT
EXISTS BETWEEN THE HIGH CENTER AND THE FRONT AND IS RESULTING IN
ADVISORY CONDITIONS OVER THE NE GULF. SATELLITE IMAGERY INDICATES
PLENTY OF UPPER LEVEL CLOUDS SCOOTING ACROSS THE GULF COAST STATES S
OF THE JET...AND WE ARE ALSO SEEING AN EXPANDING MID LEVEL DECK OVER
N FL AND THE NRN GULF. DRY AND COLD AIR ADVECTION CONTINUES ACROSS
THE AREA. HOWEVER...THE LIGHT FREEZE LOOKS LIKE IT MAY BE IN
JEOPARDY ACROSS OUR NRN ZONES.
&&
.SHORT TERM...TODAY THROUGH SUN.
LITTLE HAS CHANGED OVER THE PAST 24 HOURS IN TERMS OF THE EXPECTED
DEVELOPMENT OF OUR NEXT WEATHER MAKER. WEAK ISENTROPIC ASCENT WILL
CONTINUE THE EXPANSION OF THE MID LEVEL CLOUD DECK NWD AS CLOUD
BASES GRADUALLY LOWER. HOWEVER...EVEN AS MID AND UPPER LEVELS BECOME
SATURATED...LOWER LEVELS WILL REMAIN QUITE DRY. THE RAIN THAT
INITIALLY FALLS FROM THE CLOUDS WILL EVAPORATE AS VIRGA. THIS IS A
COOLING PROCESS THAT WILL REINFORCE THE ALREADY COOL AIR MASS
CURRENTLY IN PLACE. MAX TEMPS WILL BE HELD IN THE 40S TODAY OVER
MOST OF THE FORECAST AREA...EXCEPT ALONG THE COAST AND IN THE SE BIG
BEND...AND EVEN THESE AREAS WILL ONLY PEAK IN THE LOWER 50S. BY
AFTERNOON...ENOUGH MOISTENING WILL OCCUR THAT A FEW DROPS WILL BE
ABLE TO REACH THE GROUND. AND POPS RANGE FROM 40 FAR SE TO SILENT 10
OVER OUR NRN TIER ZONES. ISENTROPIC ASCENT WILL CONTINUE TO INCREASE
TONIGHT AND THE LOW LEVEL DRY AIR SHOULD BE COMPLETELY GONE SOMETIME
AFTER MIDNIGHT. POPS WERE KEPT IN THE LIKELY RANGE FOR ALL BUT OUR
NRN TIER GA ZONES. THE MIN TEMP TONIGHT IS EXPECTED BEFORE MIDNIGHT
WITH TEMPS RISING THEREAFTER. THE UPGLIDE IS EXPECTED TO PEAK DURING
THE FIRST HALF OF SAT. POPS WERE UPPED TO 90 AND WE INCLUDED LOCALLY
HEAVY RAIN IN THE FORECAST WITH SCATTERED CONVECTION ELEVATED ABOVE
THE STABLE SURFACE LAYER. THE STRONGEST FORCING WILL LIFT N OF THE
AREA SAT NIGHT AND POPS WILL BEGIN TO TAPER FROM S TO N. TEMPS WILL
ONCE AGAIN RISE THROUGH MUCH OF THE NIGHT AS A WARM FRONT PUSHES
INLAND ACROSS THE FORECAST AREA. SUN WILL BE DRAMATICALLY WARMER AND
MORE HUMID THAN SAT WITH DEW POINTS SURGING INTO THE 60S AND MAX
TEMPS PEAKING SOME 20 DEGREES HIGHER IN THE WARM SECTOR. LOOK FOR
HIGHS FROM THE UPPER 60S OVER SE AL AND ADJACENT SW GA TO THE MID TO
UPPER 70S ACROSS THE FL BIG BEND.
.LONG TERM...SUN NIGHT THROUGH FRI.
THE FIRST HALF OF THE EXTENDED FORECAST PERIOD WILL CONTINUE ITS
ACTIVE TREND. CYCLONIC FLOW ALOFT IN ADVANCE OF A DEVELOPING
MID-UPPER LEVEL TROUGH OVER THE NATION/S MIDSECTION WILL KEEP
WEATHER CONDITIONS UNSETTLED AND UNSEASONABLY WARM ACROSS THE GULF
STATES MONDAY THROUGH TUESDAY. DEEP LAYER MOISTURE FROM THE GULF OF
MEXICO WILL INTERACT WITH AN APPROACHING SURFACE COLD FRONT FROM THE
NORTHWEST TO PRODUCE SCATTERED SHWRS AND TSTMS...WITH STRONG TSTMS
POSSIBLE ON TUESDAY. THEN THE AFOREMENTIONED TROUGH WILL DEEPEN OVER
THE EASTERN CONUS WITH ITS AXIS OFFSHORE OF THE ATLANTIC COAST ON
WEDNESDAY. STRONG SURFACE HIGH PRESSURE CENTERED OVER THE MISSOURI
VALLEY WILL SETTLE INTO THE SOUTHEAST CONUS FOR THE LATTER HALF OF
THE WEEK...USHERING IN MUCH COOLER AND DRIER AIR. THERE IS THE
POTENTIAL FOR A LIGHT FREEZE THURSDAY MORNING.
&&
.MARINE...TODAY THROUGH TUE.
WILL HAVE TO REISSUE THE SMALL CRAFT ADVISORY FOR THE NEAR SHORE
LEGS FROM THE OCHLOCKONEE RIVER W BASED ON WHAT WE ARE SEEING AT THE
C TOWER AND NEARSHORE POINTS OFF THE MS/AL COAST. FOR EXAMPLE...BUOY
42012 IS JUST OVER 5 MILES FROM THE COAST AND HAS BEEN SUSTAINED
ABOVE 20 KT FOR A FEW HOURS NOW IN A SIMILAR GRADIENT TO THE ONE WE
ARE SEEING OVER OUR WATERS. IN ADDITION...THE COLD ADVECTION WE ARE
SEEING TONIGHT CREATES EFFICIENT MIXING OVER THE RELATIVELY MILD
GULF WATERS. THE LATEST WRF RUN INDICATES WINDS STAYING ABOVE 20 KT
UNTIL MIDDAY. AFTER A BRIEF LULL...WINDS PICK BACK UP THIS EVENING.
WE THEREFORE KEPT THINGS SIMPLE AND MAINTAINED THE ADVISORY THROUGH
12Z SAT. AFTER THE WARM FRONT LIFTS N OF THE AREA...WINDS WILL VEER
TO ONSHORE AND DIMINISH.
&&
.AVIATION...THROUGH 06Z SAT.
VFR CONDITION WILL CONTINUE THROUGH THE OVERNIGHT PERIOD WITH A
GRADUAL THICKENING AND LOWERING OF THE MID/HIGH LEVEL CLOUDS. CIGS
WILL CONTINUE TO LOWER THROUGH THE DAYLIGHT HOURS OF FRIDAY ALTHOUGH
STILL ANTICIPATE VFR CONDITIONS. WINDS FRIDAY WILL BE NORTHEAST
AROUND 10 KT. MVFR CIGS IN LIGHT RAIN WILL BE POSSIBLE FRIDAY
EVENING. BEYOND THE TAF PERIOD...CONDITIONS WILL DETERIORATE FROM
LATE FRIDAY NIGHT INTO SATURDAY WITH CIGS DROPPING THROUGH MVFR TO
IFR WITH WIDESPREAD PRECIP.
&&
.FIRE WEATHER...DESPITE HIGH TEMPS IN THE MID-UPPER 40S TODAY...DEW
POINTS IN THE MID-UPPER TEENS WILL RESULT IN LONG DURATIONS OF
SUB-35 PERCENT RELATIVE HUMIDITY FROM LATE MORNING THROUGH AFTERNOON
FOR ALL BUT TAYLOR...LAFAYETTE AND DIXIE COUNTIES IN NORTHWEST
FLORIDA. ACROSS THE NORTHERN TIER COUNTIES OF SOUTHEAST ALABAMA AND
SOUTHWEST GEORGIA...DURATIONS OF SUB-25 PERCENT RELATIVE HUMIDITY
WILL BE THREE HOURS THIS AFTERNOON. ABUNDANT LOW LEVEL MOISTURE AND
HIGH RAIN CHANCES WILL PRECLUDE RED FLAG CONCERNS THIS WEEKEND.
&&
.HYDROLOGY...THE CHOCTAWHATCHEE RIVER AT BRUCE IS NOW BELOW ITS
MODERATE FLOOD STAGE AND CONTINUES A SLOW RECESSION. STAGES WILL
LIKELY CONTINUE TO FALL TODAY AND TONIGHT. THE APALACHICOLA RIVER AT
BLOUNTSTOWN REMAINS A FEW FEET ABOVE FLOOD STAGE...BUT IS ALSO IN
SLOW RECESSION. LOCALLY HEAVY RAINFALL ON SAT COULD REVERSE THESE
TRENDS.
&&
.PRELIMINARY POINT TEMPS/POPS...
TALLAHASSEE 47 41 54 53 75 / 30 60 90 60 50
PANAMA CITY 53 44 57 55 73 / 30 70 90 70 50
DOTHAN 48 39 47 47 67 / 20 60 90 80 60
ALBANY 48 36 49 46 70 / 10 50 90 80 60
VALDOSTA 48 39 54 51 74 / 20 60 90 70 50
CROSS CITY 53 46 65 57 78 / 40 60 80 50 40
APALACHICOLA 50 45 60 57 73 / 30 60 80 60 40
&&
.TAE WATCHES/WARNINGS/ADVISORIES...
AL...NONE.
GA...NONE.
FL...RED FLAG WARNING 16-23Z TODAY FOR THE FOLLOWING ZONES:
BAY...CALHOUN...COASTAL WALTON...FRANKLIN...GADSDEN...GULF...
HOLMES...INLAND WALTON...JACKSON...JEFFERSON...LEON...
LIBERTY...MADISON...WAKULLA...WASHINGTON.
GM...SMALL CRAFT ADVISORY UNTIL 12Z SATURDAY FOR THE FOLLOWING
ZONES: COASTAL WATERS FROM OCHLOCKONEE RIVER TO APALACHICOLA FL
OUT TO 20 NM...COASTAL WATERS FROM APALACHICOLA TO DESTIN FL
OUT 20 NM...WATERS FROM SUWANNEE RIVER TO APALACHICOLA FL FROM
20 TO 60 NM...WATERS FROM APALACHICOLA TO DESTIN FL FROM 20 TO
60 NM.
&&
$$
AVIATION/FIRE WX/LONG TERM...JAMSKI
REST OF DISCUSSION...WOOL
