SWODY1
SPC AC 300549
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1149 PM CST SAT NOV 29 2008
VALID 301200Z - 011200Z
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS SERN GA AND THE FL
PENINSULA...
...SYNOPSIS...
AN UPPER LONGWAVE TROUGH IS EXPECTED TO UNDERGO FURTHER DEEPENING
EAST OF THE ROCKIES TODAY...WITH 60-120 METER HEIGHT FALLS EXTENDING
SWD INTO THE NRN GULF OF MEXICO. HEIGHT GRADIENT IN THE MID/UPPER
LEVELS WILL TIGHTEN AS THE TROUGH DEEPENS RESULTING IN STRONG WIND
FIELDS EXTENDING FROM THE HIGH PLAINS INTO THE GULF/SERN STATES TO
THE EAST COAST.
AT 12Z...A SURFACE LOW SHOULD BE LOCATED OVER WRN/CENTRAL GA WITH A
COLD FRONT TRAILING SWWD THROUGH THE FL PANHANDLE TO THE NERN AND
CENTRAL GULF OF MEXICO. THIS LOW IS FORECAST TO TRACK NEWD THROUGH
THE CAROLINAS/MID ATLANTIC REGION...IN LEE OF THE APPALACHIANS...AND
SHOULD REACH THE NERN STATES BY 12Z MONDAY. THE COLD FRONT WILL
REMAIN PROGRESSIVE THIS FORECAST PERIOD...MOVING ACROSS SRN GA AND
THROUGH FL TO WELL OFFSHORE THE MID/SRN ATLANTIC COAST BY 12Z
MONDAY. THE SRN EXTENT OF THE FRONT SHOULD BE LOCATED ALONG OR JUST
OFF THE SRN TIP OF FL BY END OF THE PERIOD.
...SERN GA/FL...
MOISTURE RETURN IS EXPECTED TO INCREASE THROUGH THE FORECAST PERIOD
AS LOW LEVEL SLY WINDS STRENGTHEN TO 50+ KT IN RESPONSE TO THE
DEEPENING LONG WAVE TROUGH. SURFACE DEWPOINTS IN THE MID 60S APPEAR
LIKELY INTO PARTS OF NRN-CENTRAL FL BY EARLY AFTERNOON...WITH VALUES
IN THE LOWER 70S POSSIBLE ACROSS THE SRN PENINSULA. MID LEVEL LAPSE
RATES WILL REMAIN RATHER WEAK ACROSS THIS REGION. HOWEVER...THE
EXPECTED INCREASE IN BOUNDARY LAYER MOISTURE COMBINED WITH SURFACE
HEATING WILL RESULT IN A MODERATELY UNSTABLE /MLCAPE 1000-1500 J/KG/
AIR MASS FROM SRN/CENTRAL TO PERHAPS NERN FL.
ALTHOUGH INSTABILITY SHOULD BE WEAK ACROSS NRN FL/SRN GA THIS
MORNING INTO THE AFTERNOON...A NARROW BAND OF FORCED ASCENT/
MOISTENING ALONG PRIMARY WIND SHIFT SHOULD RESULT IN A LOW TOPPED
SQUALL LINE SPREADING EWD ACROSS SRN GA/NRN FL. THE STRENGTH OF THE
LOW LEVEL WIND FIELD SUGGESTS THE POTENTIAL FOR STRONG/DAMAGING WIND
GUSTS WITH THIS ACTIVITY. THIS SCENARIO IS SUPPORTED BY THE 00Z 4
KM WRF-NMM WITH THE COLD FRONT/SQUALL LINE REACHING A LINE FROM
SRQ-DAB BY MID-LATE AFTERNOON.
FARTHER S...GREATER MOISTURE/STRONGER INSTABILITY /MLCAPE UP TO 1500
J/KG/ COMBINED WITH STRONG DEEP LAYER AND LOW LEVEL SHEAR /SFC-1 KM
SRH AROUND 300 M2/S2/ WILL PROVE FAVORABLE FOR SUPERCELL DEVELOPMENT
BY LATE AFTERNOON. THIS ACTIVITY SHOULD DEVELOP ALONG A PRE-FRONTAL
CONFLUENCE ZONE EXTENDING FROM THE GULF INTO S FL. ISOLATED
TORNADOES AND DAMAGING WINDS WILL BE THE PRIMARY THREATS WITH THIS
ACTIVITY. THE SEVERE THREAT SHOULD PERSIST INTO THE EVENING ACROSS
S FL...WITH OVERALL THREAT DIMINISHING BY LATE EVENING AS THE
BOUNDARY LAYER STABILIZES.
..PETERS/SMITH.. 11/30/2008
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