SWODY1
SPC AC 110057
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0657 PM CST WED DEC 10 2008
VALID 110100Z - 111200Z
...THERE IS A SLGT RISK OF SVR TSTMS PORTIONS CENTRAL SC TO FL
PANHANDLE...
...SYNOPSIS...
IN MID-UPPER LEVELS...LARGE SCALE PATTERN INCLUDES MEAN TROUGHING
FROM HUDSON BAY REGION TO W-CENTRAL GULF...FRAMED BY BROADLY
CYCLONIC FLOW COVERING MUCH OF CONUS. SHORTWAVE CYCLONE -- NOW
EVIDENT IN MOISTURE CHANNEL IMAGERY AND VWP/PROFILER WINDS OVER
UPPER TX COASTAL PLAIN -- IS FCST TO MOVE GENERALLY EWD ALONG
REMAINDER UPPER TX AND LA COASTLINE THROUGH REMAINDER PERIOD. AS
THIS OCCURS...EXPECT SFC LOW -- ANALYZED AT 23Z JUST S OF AL COAST
-- TO MOVE INLAND W-CENTRAL FL PANHANDLE. THIS LOW IS FCST TO DEEPEN
SLIGHTLY...WHILE COLD FRONT SHARPENS TO ITS S -- AS UPPER LOW APCHS.
MEANWHILE...SYNOPTIC FRONTAL ZONE WILL REMAIN QUASISTATIONARY FROM
SERN AL NEWD ACROSS WRN CAROLINAS. EFFECTIVE BAROCLINIC BOUNDARY --
HOWEVER...WILL REMAIN FARTHER E ALONG E EDGE OF CONVECTIVE PLUME
FROM SRN GA ACROSS CENTRAL NC.
...SERN CONUS...
BAND OF SCATTERED-NUMEROUS TSTMS IS FCST TO MOVE SLOWLY EWD ACROSS
CATEGORICAL OUTLOOK AREA THROUGH REMAINDER PERIOD...WITH POTENTIAL
FOR EMBEDDED LEWPS/BOWS/SUPERCELLS. DAMAGING GUSTS AND A FEW
TORNADOES ARE POSSIBLE. SECONDARY AREA OF CONVECTION -- NOW EVIDENT
AS THIN BAND OFFSHORE SC -- MAY AFFECT PORTIONS SC/NC COAST AND
NEARBY INLAND ZONES. VERTICAL SHEAR PROFILES IN EACH AREA WILL BE
FAVORABLE FOR SVR AMIDST AT LEAST MRGL BUOYANCY. THREAT SHOULD CARRY
OVER PAST 12Z INTO UPCOMING FCST PERIOD AS WELL. MAIN LIMITING
FACTORS WILL BE CONVECTIVE MODE AND LACK OF MORE ROBUST INSTABILITY.
HOWEVER...SVR PROBABILITIES REMAIN AOA CATEGORICAL RISK THRESHOLDS
FOR NOW.
SFC ANALYSIS SHOWS RESIDUAL POCKET OR RIBBON OF RELATIVELY WEAK
MOISTURE -- I.E. DEW POINTS MID 60S F -- LEFTOVER FROM S-CENTRAL FL
NWD UP SPINE OF PENINSULA AND OVER PORTIONS SERN GA -- AT LEAST
PARTLY PRODUCED BY DIURNAL HEATING/MIXING EFFECTS. AS BOUNDARY
LAYER SLIGHTLY DECOUPLES OVERNIGHT...DRY RIBBON SHOULD MIX
HORIZONTALLY AND BECOME MORE DIFFUSE...AMIDST BROADER/MESO-ALPHA
SCALE THETAE ADVECTION AND MOISTURE TRANSPORT REGIME. OBSERVED/00Z
TLH/CHS RAOBS SHOWED EFFECTIVE LIFTED PARCELS ROOTED AT SFC BECAUSE
OF RELATIVELY HIGH LOW LEVEL THETAE...EVEN THOUGH SLGT THERMAL
INVERSION WAS EVIDENT AT TLH. THIS PROFILE SHOULD BE MAINTAINED
THROUGH MOST OF NOCTURNAL HOURS IN PRECONVECTIVE BOUNDARY LAYER...AS
WAA LARGELY OFFSETS TENDENCY FOR GRADUAL/DIABATIC SFC COOLING.
ALTHOUGH LAPSE RATES ALOFT WILL REMAIN WEAK...THEY WERE SOMEWHAT
LARGER AT 00Z THAN FCST BY EITHER 21Z RUC OR 15Z NAM-KF AT
TLH/CHS...LEADING TO UNDERFCST OF BUOYANCY IN BOTH MODELS...AND
UNDER-ANALYSIS OF CAPE IN RUC BASED OBJECTIVE ANALYSIS FIELDS
PRODUCED SO FAR.
ALTHOUGH CONVECTIVE MODE WILL REMAIN LARGELY LINEAR AND
CLUSTERED...TWO FACTORS WILL MAINTAIN SLGT TORNADO RISK...
1. POTENTIAL FOR EMBEDDED MESOCIRCULATIONS WITH ACCESS TO INFLOW AIR
WITH MLCAPES IN 500-1000 J/KG RANGE BEFORE 06Z...AND 250-500 J/KG
THEREAFTER.
2. FCST STRENGTHENING OF LOW LEVEL SHEAR PROFILES OVER PORTIONS FL
PANHANDLE AND SRN GA LATE TONIGHT...AMIDST ISALLOBARIC RESPONSE TO
STRENGTHENING/APCHG SFC CYCLONE. DEEP-LAYER/EFFECTIVE SHEAR 40-50
KT WILL REMAIN POSSIBLE OVER MUCH OF SWATH ALONG/AHEAD OF MAIN BAND
OF CONVECTION. LATE TONIGHT...ISOLATED/SEGMENTED CONVECTION MAY
FORM W OF MAIN BAND ALSO -- OVER NRN GULF S OF FL PANHANDLE...NEARER
TO SFC LOW AND W OF INITIAL CONVECTIVE BAND.
..EDWARDS.. 12/11/2008
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