SWODY1
SPC AC 021630
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1030 AM CST WED DEC 02 2009
VALID 021630Z - 031200Z
...THERE IS A SLGT RISK OF SVR TSTMS THROUGH TONIGHT FOR THE SE
ATLANTIC COAST REGION...
...SYNOPSIS...
THE INITIALLY CLOSED LOW INVOF THE ARKLATEX WILL GRADUALLY EVOLVE
INTO AN OPEN WAVE AND EJECT NEWD TO THE CENTRAL APPALACHIANS
OVERNIGHT AS THIS WAVE PHASES WITH A DEEP NRN STREAM TROUGH OVER THE
NRN PLAINS AND UPPER MS VALLEY. AT THE SURFACE...A CYCLONE NOW IN
ERN MS/WRN AL WILL MOVE NEWD AND DEEPEN TO THE W OF THE APPALACHIANS
AND TOWARD THE LOWER GREAT LAKES OVERNIGHT. THE SURFACE WARM SECTOR
WILL SPREAD INLAND ACROSS GA/CAROLINAS AS THE LOW MOVES NEWD...AND A
TRAILING COLD FRONT WILL TRANSLATE EWD ACROSS THE NE GULF COAST
TODAY AND APPROACH THE SE ATLANTIC COAST AND CENTRAL FL OVERNIGHT.
THE CORRIDOR IN ADVANCE OF THE COLD FRONT WILL BE THE PRIMARY FOCUS
FOR SEVERE STORM DEVELOPMENT THROUGH TONIGHT.
...FL PANHANDLE/N FL AND S GA THROUGH EARLY TONIGHT...
AN ONGOING BROKEN BAND OF PRE-FRONTAL THUNDERSTORMS...INCLUDING
EMBEDDED SUPERCELLS...WILL CONTINUE TO SPREAD EWD ACROSS N FL AND S
GA THROUGH THE AFTERNOON IN ADVANCE OF THE COLD FRONT...WITH
ADDITIONAL DEVELOPMENT POSSIBLE ALONG THE FRONT THIS AFTERNOON.
MODEST DAYTIME HEATING HAS ALLOWED MID-UPPER 60S DEWPOINTS TO MIX
DOWN TO THE SURFACE ACROSS N FL/S GA...AND HORIZONTAL MOISTURE
ADVECTION WILL CONTINUE TODAY ACROSS THE FL PENINSULA AND OFF THE
ERN GULF OF MEXICO. DESPITE RATHER POOR MID LEVEL LAPSE RATES AOB 6
C/KM...THE INCREASING LOW-LEVEL MOISTURE AND GRADUALLY WARMING
BOUNDARY LAYER WILL CONTRIBUTE TO AFTERNOON MLCAPE VALUES OF
500-1000 J/KG. MEANWHILE...KINEMATIC FIELDS REMAIN QUITE STRONG
WITH 50-80 KT LOW-MID LEVEL FLOW WITHIN THE WARM SECTOR. RESULTANT
VERTICAL SHEAR IS ALSO STRONG WITH 0-1 KM SRH OF 300-600 M2/S2 AND
0-6 KM BULK SHEAR OF 50-75 KT. THIS COMBINATION OF INGREDIENTS WILL
SUPPORT A CONTINUED THREAT FOR DAMAGING WINDS AND A FEW TORNADOES
WITHIN THE BROKEN BANDS OF STORMS THROUGH THE AFTERNOON/EVENING.
THE COLD FRONT WILL MOVE INTO CENTRAL FL BY THE END OF THE PERIOD.
THOUGH WIND PROFILES WILL BECOME MORE UNIDIRECTIONAL WITH WEAKER
LOW-LEVEL SHEAR IN THE WARM SECTOR...THERE WILL STILL BE SOME
POTENTIAL FOR ISOLATED DAMAGING WINDS AND PERHAPS A BRIEF TORNADO
OVERNIGHT INTO CENTRAL FL.
...CAROLINA COASTAL PLAINS LATER THIS AFTERNOON/TONIGHT...
WIDESPREAD CLOUDS AND PRECIPITATION WILL PERSIST THROUGH THE DAY
ACROSS THE CAROLINAS. STILL...THE COASTAL FRONT IS EXPECTED TO MOVE
INLAND IN RESPONSE TO CYCLOGENESIS FARTHER TO THE W. AS THE MID
LEVEL TROUGH AND ASSOCIATED STRONG WIND PROFILES SPREAD NEWD...THE
EXPANDING WARM SECTOR ACROSS THE ERN CAROLINAS WILL SUPPORT AN
INCREASING THREAT FOR SUPERCELLS WITH TORNADOES AND DAMAGING WINDS
BEGINNING LATER THIS AFTERNOON AND CONTINUING THROUGH TONIGHT.
THE COMBINATION OF MID-UPPER 60S DEWPOINTS /NOW OBSERVED JUST
OFFSHORE/ AND STRONG VERTICAL SHEAR WILL BE FAVORABLE FOR SUPERCELLS
LATER THIS AFTERNOON NEAR THE COAST...ALONG THE RETREATING COASTAL
FRONT. SOME POTENTIAL FOR ISOLATED WARM SECTOR STORMS WILL CONTINUE
AFTER THE COASTAL FRONT SPREADS INLAND. TONIGHT...THE SYNOPTIC COLD
FRONT WILL APPROACH FROM THE W AND SUPPORT A LINE OF THUNDERSTORMS
WITH EMBEDDED BOW/SUPERCELL STRUCTURES CAPABLE OF PRODUCING DAMAGING
WINDS AND A FEW TORNADOES. THE SEVERE THREAT WILL END BY 12Z
THURSDAY AS THE FRONT MOVES OFFSHORE.
...NE AL/NW GA AREA LATER THIS AFTERNOON/EVENING...
SOME LOW-LEVEL DESTABILIZATION WILL OCCUR IN THE WAKE OF THE MORNING
RAINFALL...ALONG THE SURFACE COLD FRONT AND WITHIN THE MID LEVEL DRY
SLOT THIS AFTERNOON. INSTABILITY MAY BECOME SUFFICIENT FOR A NARROW
BAND OF LOW-TOPPED CONVECTION ALONG THE FRONT...WITH THE POTENTIAL
FOR ISOLATED STRONG/DAMAGING WINDS.
..THOMPSON/JEWELL.. 12/02/2009
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