SWODY1
SPC AC 020544
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1144 PM CST TUE DEC 01 2009
VALID 021200Z - 031200Z
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS THE NORTHEAST
GULF/SOUTHEAST STATES TO CAROLINAS/SOUTHEAST VA...
...SYNOPSIS...
CLOSED MID/UPPER LEVEL LOW...CENTERED OVER E TX AT 12Z TODAY...WILL
EVOLVE INTO AN OPEN WAVE OVER THE MID SOUTH/CENTRAL GULF COAST
STATES...AND THEN DE-AMPLIFY AS IT ACCELERATES NEWD AS A COMPACT
SHORTWAVE TROUGH...REACHING PA/NY BY 12Z THURSDAY. THE FAST NEWD
PROGRESSION OF THIS SYSTEM WILL OCCUR ALONG THE ERN PERIPHERY OF A
LARGE LONGWAVE TROUGH DEVELOPING OVER MUCH OF THE COUNTRY THIS
FORECAST PERIOD.
IN THE LOW LEVELS...PRIMARY SYNOPTIC SURFACE LOW IS EXPECTED TO
TRACK NEWD FROM NWRN MS INTO WRN/CENTRAL KY BY EARLY EVENING AND
THEN PROCEED TOWARD THE LOWER GREAT LAKES. A WARM SECTOR WILL
SPREAD NWD ACROSS THE NERN GULF/SERN STATES AND ATLANTIC COAST
STATES IN CONJUNCTION WITH NEWD TRACK OF THE SYNOPTIC LOW. A
TRAILING COLD FRONT IS EXPECTED TO SWEEP EWD FROM THE MID SOUTH/
CENTRAL GULF COAST REGION TO OFF THE MID ATLANTIC AND MUCH OF SRN
ATLANTIC COASTS BY THE END OF THE FORECAST PERIOD. SRN EXTENT OF
THIS FRONT SHOULD EXTEND THROUGH THE CENTRAL FL PENINSULA BY 12Z
THURSDAY.
PRIMARY DEEP CONVECTIVE POTENTIAL FOR THE PERIOD AND ATTENDANT/LONG
DURATION SEVERE WEATHER EVENT REMAINS LIKELY ACROSS THE NERN GULF
COAST STATES FROM 12Z TODAY INTO THE AFTERNOON...WITH THE THREAT
THEN SHIFTING ACROSS THE CAROLINAS/SERN VA BY LATE AFTERNOON/EARLY
EVENING INTO WEDNESDAY NIGHT.
...NORTHEAST GULF/SOUTHEAST STATES TO CAROLINAS/SOUTHEAST VA...
AT 12Z TODAY...TSTMS...SOME SEVERE...ARE EXPECTED TO BE ONGOING
ACROSS SRN AL/WRN FL PANHANDLE AND SSWWD INTO THE GULF ALONG THE
COLD FRONT. STRONG SLY LOW LEVEL FLOW DEVELOPING IN ADVANCE OF THE
COLD FRONT WILL MAINTAIN A RETURN FLOW OF MOISTURE FROM THE ERN GULF
AND SRN ATLANTIC INTO THE SLIGHT RISK AREA TODAY. ALTHOUGH LAPSE
RATES WILL BE WEAK...SURFACE DEWPOINTS IN THE MID-UPPER 60S
SPREADING ACROSS THE NERN GULF COAST STATES THIS MORNING AND
AFTERNOON WILL CONTRIBUTE TO MLCAPE VALUES 500-1000 J/KG. A SIMILAR
MOIST/UNSTABLE AIR MASS IS EXPECTED INTO THE CAROLINAS/SERN VA BY
THIS EVENING INTO THE OVERNIGHT PERIOD AS THE COLD FRONT SWEEPS
TOWARD THIS REGION.
FORCING FOR ASCENT WITHIN ENTRANCE REGION OF A 100 KT SWLY MID LEVEL
JET ACCOMPANYING THE ACCELERATING UPPER TROUGH COMBINED WITH LOW
LEVEL WAA WILL MAINTAIN LIKELIHOOD FOR TSTM ACTIVITY TO PROGRESS EWD
ALONG THE COLD FRONT WITH POTENTIAL FOR DISCRETE STORMS WITHIN THE
WARM SECTOR. DESPITE WEAK INSTABILITY...STRONG EFFECTIVE BULK SHEAR
/UP TO 50 KT/ AND 0-1 KM SRH 200-300 M2/S2 WILL FAVOR THE POTENTIAL
FOR BOTH DAMAGING WINDS AND TORNADOES. AS THE COLD FRONT PROGRESSES
EWD TO CENTRAL GA/NWRN FL BY 03/00Z...A MORE UNSTABLE AIR MASS IS
EXPECTED TO DEVELOP DOWNSTREAM INTO THE CAROLINAS ALLOWING FOR AN
INCREASE IN THE SEVERE WEATHER THREAT /DAMAGING WINDS AND TORNADOES/
FROM ERN GA INTO THE CAROLINAS AND SERN VA DURING THE LATTER HALF OF
THE PERIOD.
SEVERE WEATHER THREAT WILL ALSO CONTINUE INTO THE NRN HALF OF FL
THIS EVENING AS THE COLD FRONT MOVES SEWD ACROSS THIS STATE.
...NRN AL TO ERN KY...
ALTHOUGH MOISTURE RETURN WILL BE MUCH LESS THAN FARTHER S...WITH
SURFACE DEWPOINTS INTO THE UPPER 40S POSSIBLE...STEEPER MID LEVEL
LAPSE RATES ACCOMPANYING THE SHORTWAVE TROUGH SHOULD RESULT IN WEAK
INSTABILITY. THIS COMBINED WITH EFFECTIVE BULK SHEAR 25-30 KT
SUGGESTS A FEW MAINLY ELEVATED STORMS MAY BE CAPABLE OF PRODUCING
HAIL.
..PETERS.. 12/02/2009
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