FXUS62 KTAE 292058
AFDTAE
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TALLAHASSEE FL
358 PM EST SUN NOV 29 2009
...SIGNIFICANT HAZARDOUS WEATHER EVENT POSSIBLE BY MID
WEEK...WHICH MAY INCLUDE SEVERE STORMS...INLAND FLOODING FROM
HEAVY RAIN...COASTAL FLOODING...AND GALE CONDITIONS OVER THE
GULF OF MEXICO...
.SYNOPSIS...
THE 20 UTC REGIONAL SURFACE ANALYSIS SHOWED AN AREA OF HIGH
PRESSURE RETREATING INTO THE ATLANTIC AS A COLD FRONT APPROACHED
THE SOUTHEAST U.S. FROM THE NORTHWEST. VAPOR IMAGERY AND UPPER AIR
DATA SHOWED A STRONG CLOSED LOW OVER THE BAJA PENINSULA. THIS
SYSTEM WILL HAVE A MAJOR IMPACT ON OUR AREA BY MID WEEK.
&&
.SHORT TERM...
(TONIGHT THROUGH WEDNESDAY) THE AFOREMENTIONED COLD FRONT WILL
MOVE SOUTHEAST THROUGH OUR FORECAST AREA MONDAY AND MONDAY
NIGHT...BRINGING WITH IT A CHANCE FOR MAINLY LIGHT RAIN. THE BEST
CHANCE OF RAIN WILL BE IN SOUTHEAST AL AND CENTRAL GA WHERE THERE
WILL BE MORE DEEP LAYER MOISTURE AND LIFT. THE FRONT IS FORECAST
TO STALL ACROSS CENTRAL FL AND THE CENTRAL GULF AS A SURFACE LOW
QUICKLY DEVELOPS OFF THE TX COAST...IN RESPONSE TO AN APPROACHING
STRONG 500 MB SHORT WAVE (CURRENTLY OVER THE BAJA). THE GFS/ECMWF
CONSENSUS RAPIDLY DEEPENS THE SURFACE LOW AS IT MOVES
NORTHEASTWARD TUESDAY NIGHT AND WEDNESDAY...MOVING INLAND ACORSS
MS OR AL. THIS SYSTEM HAS THE CAPABILITY OF CAUSING A MULTI-
FACETED HAZARDOUS WEATHER EVENT FOR OUR AREA TUESDAY NIGHT AND
WEDNESDAY...INCLUDING SEVERE STORMS...INLAND FLOODING FROM HEAVY
RAIN...COASTAL STORM SURGE FLOODING...HIGH SURF...AND GALE FORCE
WIND GUSTS.
CONFIDENCE IN THIS SIGNIFICANT WEATHER EVENT IS INCREASING GIVEN
THE CONSISTENCY BETWEEN DIFFERENT MODELS AND WITHIN EACH MODEL
RUN. THERE WILL BE TWO DISTINCT CHANCES FOR SEVERE WEATHER...ONE
WITH DISCRETE SUPERCELLS FORMING ALONG THE WARM FRONT LATE TUESDAY
NIGHT...AND THE MORE LIKELY SCENARIO WHERE A SQUALL LINE BARRELS
THROUGH THE REGION DURING THE DAY ON WEDNESDAY. THE LATEST GFS RUN
NOW FORECASTS MORE SURFACE INSTABILITY THAN PREVIOUS
RUNS...ALLOWING THE MARITIME TROPICAL AIRMASS TO MOVE WELL INLAND
DURING THE HEAT OF THE DAY. ADD TO THIS THE EXTREMELY FAVORABLE
VERTICAL WIND SHEAR (55-65KT 0-6KM AND 40KT 0-1KM) AND STRONG
LARGE SCALE FORCING...AND AT LEAST A FEW STORMS COULD BECOME
SEVERE. DAMAGING STRAIGHT LINE WIND GUSTS...LARGE HAIL...AND
ISOLATED TORNADOES ARE ALL APPEAR POSSIBLE. EVEN THE FORECAST
700-500MB LAPSE RATES ARE STEEPER THAN USUAL AT ABOUT 6C/KM.
IF THIS SQUALL LINE IS STRONG AND LARGE ENOUGH (AS INDICATED BY
THE GFS)...IT MAY CONTRIBUTE TO THE PILING UP OF WATER INTO
APALACHEE BAY. THIS COULD CAUSE STORM TIDES OF 4 TO 6 FEET ALONG
PORTIONS OF APALACHEE BAY...MAINLY FROM ST MARKS EASTWARD
WEDNESDAY AND WEDNESDAY NIGHT. IF STRONG VERTICAL MIXING DEVELOPS
DURING THE DAY ON WEDNESDAY...WINDS MAY GUST TO 40 MPH INLAND.
.LONG TERM...
(WEDNESDAY NIGHT THROUGH SUNDAY)...RAIN CHANCES WILL TAPER OFF
WEDNESDAY NIGHT AS THE SURFACE AND UPPER LOW DEPART TO THE
NORTHEAST. HIGH PRESSURE WILL BUILD INTO THE REGION ALONG WITH
DRIER AND COOLER TEMPERATURES FOR FRIDAY AND SATURDAY AND THEN
JUST A SLIGHT CHANCE OF RAIN ON SATURDAY AHEAD OF THE NEXT COLD
FRONT.
&&
.AVIATION...
HIGH PRESSURE WILL SLIDE TO THE EAST THROUGH TONIGHT AS A WEAK
COLD FRONT APPROACH FROM THE NORTHWEST. VFR CONDITIONS SHOULD
PREVAIL THROUGH THE OVERNIGHT UNDER INCREASING MID AND HIGH LEVEL
CLOUDS. SCT LOWER LEVEL CLOUDS WILL BE ON THE INCREASE FROM NW TO
SE WITH THE ADVANCING FRONT DURING MONDAY. GENERAL VFR CONDITIONS
TO CONTINUE THROUGH THE TAF PERIOD...HOWEVER COULD SEE A BRIEF
PERIOD OF MVFR CIGS WITH A SHOWER OR TWO AROUND KDHN BY MIDDAY.
LOOKING INTO THE MIDDLE OF THE WEEK. AN EXTENDED PERIOD OF
SIGNIFICANT CIG AND/OR VIS RESTRICTIONS ARE EXPECTED BEGINNING
TUESDAY AFTERNOON INTO WEDNESDAY AS A POTENTIALLY STRONG AREA OF
LOW PRESSURE MOVES ACROSS THE AREA. THIS AREA OF LOW PRESSURE WILL
HAVE THE POTENTIAL TO BRING HEAVY RAIN...STRONG THUNDERSTORMS...AND
STRONG GUSTY WINDS TO THE TERMINALS. PILOTS SHOULD PAY CLOSE
ATTENTION TO FORECASTS DURING THE NEXT DAY OR TWO WITH RESPECT TO
THIS POTENTIAL STORM BEFORE MAKING ANY FLIGHT PLANS.
&&
.MARINE...
WINDS AND SEAS WERE VERY LOW THIS AFTERNOON...BUT WILL SLOWLY PICK
BEHIND THE FRONT MONDAY NIGHT...THEN RAPIDLY INCREASE TUESDAY AND
TUESDAY NIGHT AS THE LOW WINDS UP. SUSTAINED GALE FORCE WINDS ARE
POSSIBLE...BUT FOR NOW WE USED AN AVERAGE OF THE GFS...NAM...AND
ECMWF WHICH YIELDS SUSTAINED WINDS SLIGHTLY BELOW GALE FORCE (AS
THE NAM AND ECMWF WINDS WERE SLIGHTLY BELOW THE GFS). BECAUSE OF THAT
ADJUSTMENT WE WENT A LITTLE BELOW THE GFS-BASED WAVEWATCH MODEL AS
WELL. IF SUBSEQUENT MODEL RUNS COME IN TO BETTER AGREEMENT WITH
THE GFS WE MAY HAVE TO RAISE OUR WINDS AND SEAS FORECAST. HIGH
SURF IS LIKELY WEDNESDAY AND THURSDAY...PERHAPS REACHING 10 FT AT
PORTIONS OF THE FL PANHANDLE. TIDES WILL BE WELL ABOVE NORMAL.
&&
.FIRE WEATHER...
HIGH PRESSURE WILL SLIP EAST TONIGHT AS A WEAK COLD FRONT APPROACHES
FROM THE NORTHWEST. LOW LEVEL MOISTURE WILL INCREASE AHEAD OF THIS
FRONT BEFORE IT PASSES THROUGH THE REGION MONDAY AFTERNOON AND
MONDAY NIGHT. MAY SEE A BRIEF PERIOD OF DRIER AIR ARRIVE EARLY ON
TUESDAY...HOWEVER THIS DRIER AIR WILL BE BRIEF HAS LOW PRESSURE
DEVELOPS RAPIDLY IN THE WESTERN GULF OF MEXICO AND BEGINS TO EFFECT
THE REGION LATER TUESDAY INTO WEDNESDAY. THIS SYSTEM DURING THE MID
WEEK PERIOD HAS THE POTENTIAL TO BE A RATHER POTENT STORMS WILL THE
POTENTIAL FOR VERY HEAVY RAINFALL AND STRONG THUNDERSTORMS. THE
COMBINATION OF THE FRONT ON MONDAY AND THE MID-WEEK STORM WILL KEEP
CRITICAL FIRE WEATHER CONDITIONS FROM BEING REACHED THROUGH AT LEAST
WEDNESDAY.
&&
.HYDROLOGY...
THE
GFS AND ECMWF REMAIN IN GOOD AGREEMENT IN FORECASTING A NORTHEAST
TO SOUTHWEST ORIENTED RAIN BAND OF 3 TO 6 INCHES...WITH MAXIMA OF
8 TO 12 INCHES. THE MEAN OF THIS GUIDANCE PLACES THIS RAIN BAND
FROM CENTRAL GA TO THE FL PANHANDLE. NOT ONLY WILL FLASH FLOODING
BE A CONCERN...BUT RIVER FLOODING AS WELL LATE IN THE WEEK OR NEXT
WEEKEND.
.PRELIMINARY POINT TEMPS/POPS...
TALLAHASSEE 45 75 45 65 54 / 0 20 20 20 60
PANAMA CITY 55 73 48 65 57 / 0 30 20 30 70
DOTHAN 49 72 39 61 50 / 10 50 10 20 70
ALBANY 47 72 37 63 49 / 0 40 10 10 60
VALDOSTA 44 73 42 65 51 / 0 20 20 10 60
CROSS CITY 42 73 47 70 55 / 0 10 10 20 50
APALACHICOLA 52 72 49 66 58 / 0 20 20 30 60
&&
.TAE WATCHES/WARNINGS/ADVISORIES...
AL...NONE.
GA...NONE.
FL...RED FLAG WARNING UNTIL 6 PM EST THIS EVENING FOR THE FOLLOWING
ZONES: DIXIE...JEFFERSON...LAFAYETTE...MADISON...TAYLOR.
GM...NONE.
&&
$$
LONG TERM...BARRY
AVIATION/FIRE WX...MROCZKA
REST OF DISCUSSION...FOURNIER
