SWODY3
SPC AC 300829
DAY 3 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0229 AM CST MON NOV 30 2009
VALID 021200Z - 031200Z
...THERE IS A SLGT RISK OF SVR TSTMS FROM FL/SERN AL/GA NEWD ACROSS
THE ERN CAROLINAS/SERN VA...
...SYNOPSIS...
UPPER LOW CROSSING TX EARLY IN THE PERIOD IS PROGGED TO BEGIN
SHEARING/SHIFTING QUICKLY NEWD WITH TIME THIS PERIOD...AS A
LARGER/STRONGER UPPER TROUGH DIGS/EXPANDS ACROSS THE CENTRAL -- AND
EVENTUALLY INTO THE ERN -- CONUS. AS THIS OCCURS...SURFACE LOW OVER
THE CENTRAL GULF COAST REGION INITIALLY IS FORECAST TO UNDERGO RAPID
CYCLOGENESIS...SHIFTING QUICKLY NNEWD TOWARD THE LOWER GREAT LAKES
REGION. IN CONJUNCTION...A STRENGTHENING COLD FRONT WILL CROSS THE
SRN APPALACHIANS/ATLANTIC COAST STATES...APPROACHING OR REACHING THE
ATLANTIC COAST LATE. THIS FRONT/STORM SYSTEM SHOULD SUPPORT
WIDESPREAD PRECIPITATION...AND SCATTERED BANDS OF STRONG/POTENTIALLY
SEVERE STORMS THROUGH THE PERIOD.
...ERN GULF COAST REGION INTO THE SOUTHEAST/CAROLINAS/SERN VA...
ACTIVE CONVECTIVE DAY -- WITH A RESPECTABLE POTENTIAL FOR LOCALLY
SEVERE STORMS AND POSSIBLY A HIGHER-END EVENT OR TWO -- APPEARS TO
BE EVOLVING FOR DAY 3...INITIALLY ACROSS THE FL PANHANDLE AND
ADJACENT AL/GA AND THEN SPREADING EWD/NEWD ACROSS THE MIDDLE AND SRN
ATLANTIC COASTAL REGION THROUGH THE PERIOD.
ONSHORE ADVECTION OF BOTH GULF AND ATLANTIC MOISTURE IS
EXPECTED...AS THE SURFACE LOW SHIFTS NNEWD WITH TIME.
THE EXACT WWD AND NWD FRINGES OF THE BOUNDARY LAYER-BASED MOISTURE
-- AND THUS SURFACE-BASED INSTABILITY -- REMAIN UNCLEAR GIVEN
UNCERTAINTIES WITH THE SURFACE LOW TRACK AND SPEED WITH WHICH
LOW-LEVEL COOL AIR LINGERING ON WRN FRINGES OF A WRN ATLANTIC HIGH
CAN ERODE. HAVING SAID THAT...IT APPEARS ATTM THAT WEAK
SURFACE-BASED DESTABILIZATION WILL SPREAD ACROSS FL AND MUCH OF
GA...AND NEWD ACROSS THE SRN APPALACHIANS INTO AT LEAST ERN SC/ERN
NC AND EVENTUALLY SERN VA AHEAD OF THE SHARPENING/EWD-MOVING COLD
FRONT.
MODELS GENERALLY AGREE THAT WHILE PROGRESSING EWD...THE FRONT SHOULD
REMAIN ONSHORE ACROSS THE ATLANTIC COAST REGION WELL INTO THE
OVERNIGHT HOURS...ALLOWING FOR AN EXTENDED PERIOD OF
CONVECTIVE/SEVERE POTENTIAL. AN INITIAL SEVERE THREAT MAY EXIST
WITH THE NWD RETREAT OF A WARM FRONT...AND LATER WITH ONE OR MORE
BANDS OF CONVECTION AHEAD OF THE FRONT.
WHILE MODEST INSTABILITY AND STRONG FORCING/ASCENT SUGGEST
WIDESPREAD PRECIPITATION -- FURTHER HINDERING DESTABILIZATION
POTENTIAL...THIS STRONG ASCENT COMBINED WITH VERY STRONG/VEERING
FLOW WITH HEIGHT ATOP THE WARM SECTOR WILL RESULT IN CONDITIONS
QUITE FAVORABLE FOR ORGANIZED BANDS/LINES OF CONVECTION AND LOCALLY
ROTATING/SUPERCELL STORMS. GIVEN WHAT APPEARS TO BE A
DYNAMIC...LOW-CAPE/HIGH-SHEAR EVENT SETTING UP...POTENTIAL FOR AN
OVER-FORECAST OF SEVERE WEATHER EXISTS. HOWEVER...GIVEN AT LEAST
LOCALLY HIGH-END POTENTIAL ALSO EVIDENT...WILL INTRODUCE A LARGE
SLIGHT RISK AREA THIS FORECAST. WITH THE EXCEPTION OF S FL...IT
APPEARS AT THIS POINT THAT THE THREAT SHOULD END FROM W-E WITH
TIME...EVENTUALLY REACHING -- OR MOVING OFF -- THE ATLANTIC COAST
THROUGH 03/12Z.
..GOSS.. 11/30/2009
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