SWODY1
SPC AC 151258
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0658 AM CST SAT DEC 15 2007
VALID 151300Z - 161200Z
..THERE IS A SLGT RISK OF SVR TSTMS TODAY ACROSS SE TX...SRN
LA...SW MS...
..THERE IS A SLGT RISK OF SVR TSTMS THIS AFTERNOON INTO TONIGHT
FROM N FL TO THE COASTAL CAROLINAS...
..SYNOPSIS...
A STRONG MID LEVEL SHORTWAVE TROUGH OVER W TX/OK THIS MORNING WILL
PROGRESS EWD TODAY OVER THE SRN PLAINS...AND THEN ENEWD TONIGHT TO
THE OH/TN VALLEY REGION. THE ENTIRE SYSTEM WILL AMPLIFY AS THE MID
LEVEL WAVE PHASES WITH THE SURFACE WARM SECTOR ACROSS E/SE TX...AND
A WEAK SURFACE CYCLONE IN E TX DEEPENS RAPIDLY THROUGH TONIGHT WHILE
MOVING TO THE OH VALLEY. FARTHER E...SECONDARY CYCLOGENESIS IS
EXPECTED ACROSS THE SE ATLANTIC COASTAL PLAIN TONIGHT...REACHING THE
CHESAPEAKE REGION BY 16/12Z.
..SE TX/SRN LA/SW MS TODAY...
A BAND OF STRONG THUNDERSTORMS HAS EVOLVED OVERNIGHT ALONG THE
SURFACE COLD FRONT FROM E CENTRAL INTO SE TX. A NARROW WEDGE OF THE
WARM SECTOR...CONSISTING OF A MODIFIED CP AIR MASS WITH MID-UPPER 60
DEWPOINTS...HAS SPREAD INLAND ACROSS SE TX.
MOISTENING/DESTABILIZATION IS ALSO EXPECTED DURING THE DAY ACROSS
SRN LA/MS IN ADVANCE OF THE COLD FRONT. HERE...MUCAPE VALUES WILL
RANGE FROM 500-1000 J/KG.
A LLJ SEGMENT WILL DEVELOP NEWD TOWARD TN/KY WITH THE DEEPENING
SURFACE LOW...AND THIS JET WILL REMAIN LARGELY N OF THE SURFACE WARM
SECTOR TODAY. RESULTANT FORECAST HODOGRAPH STRUCTURES ARE
SUBOPTIMAL FOR SUPERCELLS/TORNADOES. STILL...WARM SECTOR VERTICAL
SHEAR SHOULD BE SUFFICIENT FOR EMBEDDED BOWING STRUCTURES...AND
PERHAPS SUPERCELLS...THROUGH TODAY. DAMAGING WINDS AND A TORNADO OR
TWO WILL BE THE MAIN SEVERE THREATS BEFORE THE BAND OF STORMS ALONG
THE COLD FRONT WEAKENS THIS EVENING.
..NE GULF COAST/SE ATLANTIC COAST THROUGH EARLY SUNDAY...
A MARITIME TROPICAL AIR MASS /BOUNDARY LAYER DEWPOINTS OF 68-74 F/
ACROSS THE NE GULF OF MEXICO/FL WILL CONTINUE TO SPREAD SLOWLY NWWD
TODAY...AND ONSHORE ACROSS SC/NC BY TONIGHT IN RESPONSE TO SECONDARY
CYCLOGENESIS ALONG THE RETREATING COASTAL FRONT. THIS MOISTURE WILL
CONTRIBUTE TO AT LEAST WEAK INSTABILITY INLAND /MUCAPE VALUES OF
500-1000 J/KG/...AND AN EXTENSIVE NNE-SSW ORIENTED BAND OF
CONVECTION WILL LIKELY EVOLVE LATER TODAY INTO TONIGHT ALONG THE NW
PERIPHERY OF THIS RICHER MOISTURE.
MEANWHILE...LOW-LEVEL AND DEEP LAYER VERTICAL SHEAR ARE FORECAST TO
BECOME QUITE STRONG TONIGHT ALONG THE RETREATING COASTAL FRONT AND
IN CONJUNCTION WITH A 50-60 KT LLJ. LONG ANTICYCLONICALLY CURVED
HODOGRAPHS WITHIN THE NARROW INLAND WARM SECTOR /AS EVIDENCED BY
EFFECTIVE SRH OF 250-400 M2/S2/ APPEAR SUPPORTIVE OF EMBEDDED
SUPERCELLS AND BOWING SEGMENTS CAPABLE OF PRODUCING DAMAGING WINDS
AND A COUPLE OF TORNADOES. THE SEVERE STORM THREAT WILL BEGIN THIS
AFTERNOON ACROSS THE FL PANHANDLE AREA AND SPREAD NEWD ACROSS SE GA
BY THIS EVENING...REACHING THE COASTAL CAROLINAS TONIGHT.
.THOMPSON.. 12/15/2007
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