SWODY1
SPC AC 020056
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0656 PM CST TUE DEC 01 2009
VALID 020100Z - 021200Z
...THERE IS A SLGT RISK OF SVR TSTMS FROM SOUTH CENTRAL/SERN LA AND
SERN MS TO SRN AL/WRN FL PANHANDLE...
...GULF COAST AREA...
THE WRN PORTION OF THE SLIGHT RISK AREA IS BEING EXTENDED WWD TO
INCLUDE COASTAL REGIONS OF SOUTH CENTRAL LA. THIS CHANGE IN THE
OUTLOOK TAKES INTO ACCOUNT AN ISOLATED TORNADO THREAT AND/OR
DAMAGING WINDS AS A SURFACE LOW...CURRENTLY FORMING OFFSHORE OF DEEP
S TX...MOVES INTO THIS REGION BETWEEN 09-12Z. THE REST OF THE
SLIGHT RISK AREA EXTENDING EWD TO THE WRN FL PANHANDLE/FAR SRN AL IS
BEING MAINTAINED WITH THIS OUTLOOK. GREATEST SEVERE WEATHER THREATS
SHOULD OCCUR BETWEEN 06-12Z ALONG COASTAL AREAS OF THE SLIGHT RISK.
EARLY EVENING SURFACE ANALYSIS SHOWED A WARM FRONT STRETCHING FROM
THE CENTRAL FL PENINSULA WNWWD INTO FAR NORTH CENTRAL GULF OF MEXICO
/E OF BVE/ WHERE IT INTERSECTS TWO BOUNDARIES 1) EXTENDING EWD INTO
NRN FL PENINSULA AND 2) EXTENDING NEWD TO SWRN AL. MEANWHILE...THE
WARM FRONT THEN EXTENDED SWWD TO A SURFACE LOW LOCATED OVER THE NWRN
GULF /NEAR BUOY 42361/. ANOTHER SURFACE BOUNDARY/INVERTED TROUGH
EXTENDED FROM SWRN MS THROUGH SWRN LA INTO THE FAR WRN GULF...WITH A
NEW SURFACE LOW EXPECTED TO FORM OFF THE DEEP S TX COAST THIS
EVENING. THE LATTER SURFACE LOW WILL BE TIED TO STRONG FORCING FOR
ASCENT ATTENDANT TO A STRONG SHORTWAVE TROUGH...INDICATED BY RECENT
INCREASE IN LIGHTNING/ COOLING CLOUD TOPS OVER MIDDLE/S TX COAST.
THE CURRENT SUBSYNOPTIC LOWS E OF BVE AND NEAR BUOY 42361 ARE
EXPECTED TO TRACK INLAND THIS FORECAST PERIOD...ALONG THE BOUNDARY
EXTENDING INTO SWRN AL. THE EXTENSIVE COVERAGE OF CLOUDS/
PRECIPITATION EXTENDING WELL INLAND ACROSS THE CENTRAL/NERN GULF
COAST STATES...N OF THE ONGOING GULF TSTM COMPLEX...SHOULD CONTINUE
TO MAINTAIN A STABLE BOUNDARY LAYER. THIS PROCESS SHOULD TEND TO
RESULT IN A WEAKENING OF THE LOWS AS THEY MOVE INLAND...AND DICTATE
A SLOW NWD SHIFT OF THE WARM FRONT THIS EVENING. HOWEVER...A
STRENGTHENING SSWLY LLJ /40-60 KT/ INTO THE CENTRAL GULF COAST
BETWEEN 06-12Z WILL LIKELY AID IN AN INTRUSION OF THE WARM/MOIST
WARM SECTOR INTO FAR SERN LA/SERN MS TO SRN AL/WRN FL PANHANDLE.
A BAND OF SWLY MID LEVEL WINDS WILL TRANSLATE ACROSS THE NRN GULF
COAST STATES OVERNIGHT AND STRENGTHEN TO 70-90 KT...AS AN UPSTREAM
MID/UPPER LEVEL LOW DEEPENS WITH THIS SYSTEM BECOMING NEGATIVELY
TILTED BY 12Z. CONCURRENT INCREASE IN EFFECTIVE BULK SHEAR TO 40-50
KT COMBINED WITH STRONG LOW LEVEL SHEAR ALONG THE WARM FRONT MOVING
INLAND LATER IN THE PERIOD AND ALONG LLJ WILL MAINTAIN A THREAT FOR
ISOLATED TORNADOES AND DAMAGING WINDS.
..PETERS.. 12/02/2009
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