SWODY1
SPC AC 260549
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1149 PM CST SUN NOV 25 2007
VALID 261200Z - 271200Z
..THERE IS A SLGT RISK OF SVR TSTMS ACROSS THE NERN GULF COAST...
..THERE IS A SLGT RISK OF SVR TSTMS ACROSS PART OF THE CAROLINAS
INTO SERN VA...
..SYNOPSIS...
MODELS ARE CONSISTENT WITH DEAMPLIFICATION OF THE SRN PLAINS MID/
UPPER LEVEL LOW INTO AN OPEN WAVE AS THIS SYSTEM TRACKS FROM ERN
OK/AR TO ERN KY/TN BY 27/00Z. FURTHER WEAKENING IS EXPECTED TONIGHT
AS THIS TROUGH MOVES RAPIDLY NEWD INTO CONFLUENT FLOW OVER THE NERN
STATES...AND IN ADVANCE OF FAST MOVING ALBERTA/NRN ROCKIES TROUGH
TRACKING TOWARD THE GREAT LAKES AND OH/TN VALLEYS. SURFACE LOW IS
EXPECTED TO DEEPEN AS IT MOVES NEWD FROM WRN TN TO THE UPPER OH
VALLEY BY EARLY THIS EVENING AND TO MAINE BY 12Z TUESDAY. TRAILING
COLD FRONT WILL REMAIN PROGRESSIVE TODAY SPREADING EWD FROM THE
AL/MS BORDER THROUGH THE SERN AND MID ATLANTIC STATES...AND OFF MUCH
OF THE ATLANTIC SEABOARD SWWD INTO CENTRAL FL BY END OF PERIOD.
THIS FRONT IS EXPECTED TO BE THE FOCUS FOR STRONG TO SEVERE TSTM
ACTIVITY INITIALLY THIS MORNING AND AFTERNOON ACROSS THE NERN GULF
COAST...AND THEN SHIFTING TO THE CAROLINAS/SERN VA FROM THE LATE
AFTERNOON INTO THE EVENING/PART OF OVERNIGHT PERIOD.
..NERN GULF COAST...
AT 12Z TODAY...A PRE-FRONTAL BAND OF TSTMS /A FEW POTENTIALLY
SEVERE/ IS EXPECTED TO BE ONGOING ACROSS PARTS OF SRN AL AND THE WRN
FL PANHANDLE WITHIN ZONE OF DEEP LAYER FORCING FOR ASCENT
ACCOMPANYING LOWER MS VALLEY UPPER LOW. DESPITE WEAKER HEIGHT FALLS
EXPECTED ACROSS THIS REGION AS STRONGER FORCING SHIFTS NEWD AWAY
FROM THE GULF COAST...FRONTAL CONVERGENCE IS EXPECTED TO MAINTAIN
TSTM DEVELOPMENT ALONG THE COLD FRONT EWD TO SRN GA/ERN FL PANHANDLE
THIS AFTERNOON. WARM SECTOR DESTABILIZATION IS EXPECTED TO
CONTRIBUTE TO MUCAPE VALUES OF 500-1000 J/KG.
DEEP LAYER SWLY SHEAR OF 40-50 KT WILL SUPPORT ORGANIZED/ROTATING
UPDRAFTS INTO THE EARLY AFTERNOON CAPABLE OF PRODUCING DAMAGING
WINDS AND AN ISOLATED TORNADO THREAT. SEVERE WEATHER THREAT AND
STORM INTENSITIES SHOULD DIMINISH BY MID AFTERNOON AS LOW LEVEL FLOW
VEERS AHEAD OF THE FRONT...WEAKENING LOW LEVEL FRONTAL CONVERGENCE.
..CAROLINAS/SERN VA...
HEIGHT FALLS WITH APPROACH OF LOWER MS VALLEY UPPER TROUGH AND TRACK
OF SURFACE LOW TOWARD THE UPPER OH VALLEY WILL SUPPORT SLY LOW LEVEL
FLOW DEVELOPING IN LEE OF THE SRN/CENTRAL APPALACHIANS TODAY. WEDGE
FRONT WILL ERODE OR RETREAT NWD INTO THE MID ATLANTIC REGION AS LOW
LEVEL MOISTURE SPREADS INLAND WITH SURFACE DEWPOINTS INCREASING
THROUGH THE 60S ALONG AND E OF THE PIEDMONT REGION OF THE CAROLINAS
TO SERN VA. DESPITE FORECAST FOR WEAK LAPSE RATES...THE MOISTURE
RETURN WILL AID IN DESTABILIZATION WITH MUCAPE VALUES UP TO 700 J/KG
ACROSS WRN PART OF SLIGHT RISK. HIGHER INSTABILITY /MUCAPE AROUND
1000 J/KG/ SHOULD OCCUR NEAR THE COAST LATER TONIGHT GIVEN FURTHER
BOUNDARY LAYER MOISTENING.
MODELS INDICATED ASCENT WITH WEAK MID LEVEL IMPULSES TRACKING NEWD
ACROSS THE CAROLINAS TO MID ATLANTIC REGION AHEAD OF THE UPPER
TROUGH SHOULD AID IN TSTM DEVELOPMENT. FORECAST SOUNDINGS SUGGEST
MUCH OF THE INLAND TSTM ACTIVITY THROUGH THIS AFTERNOON SHOULD BE
ELEVATED PRIOR TO EROSION OF WEDGE FRONT.
THEREAFTER...TSTM DEVELOPMENT SHOULD INCREASE THIS EVENING THROUGH
OVERNIGHT PERIOD FROM W-E ACROSS THE SLIGHT RISK AREA AS STRONGER
HEIGHT FALLS AND THE COLD FRONT ADVANCE EWD. DESPITE MARGINAL
INSTABILITY...INCREASING DEEP LAYER AND LOW LEVEL SHEAR SUGGEST THE
POTENTIAL FOR ORGANIZED STORMS CAPABLE OF PRODUCING EMBEDDED
SUPERCELLS AND BOWING STRUCTURES. DAMAGING WINDS SHOULD BE THE
PRIMARY THREAT GIVEN THE FORECAST FOR FAST STORM MOTIONS /40-50 KT/.
HOWEVER...STRONG LOW LEVEL SHEAR VALUES SUGGEST AN ISOLATED TORNADO
WILL BE POSSIBLE WITH ANY SUSTAINED SUPERCELLS.
.PETERS/CROSBIE.. 11/26/2007
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