SPC AC 221959
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0159 PM CST FRI FEB 22 2008
VALID 222000Z - 231200Z
...THERE IS A SLGT RISK OF SVR TSTMS LATE THIS AFTN/TONIGHT ACROSS
PARTS OF THE ERN GULF/SOUTH ATLANTIC COAST STATES....
...SOUTHEAST...
WITH AN INCREASINGLY SHEARED SOUTHERN BRANCH TROUGH LIFTING INTO A
CONFLUENT UPPER FLOW REGIME ACROSS THE OHIO VALLEY...WEAK
SUBTROPICAL SHORT WAVE IMPULSES LIFTING THROUGH THE SOUTHEASTERN
STATES APPEAR TO BE OF PRIMARY IMPORTANCE TO THE CONVECTIVE
POTENTIAL AS THEY MERGE INTO THE SOUTHERN STREAM.
THE LEAD IMPULSE ALREADY IS IN THE PROCESS OF LIFTING INTO/THROUGH
SOUTHERN MID ATLANTIC COASTAL AREAS. BUT...A TRAILING LOWER MID
TROPOSPHERIC WIND SHIFT/CONFLUENT ZONE HAS BEEN THE CONTINUING FOCUS
FOR A BAND OF THUNDERSTORMS...WELL AHEAD OF THE COLD FRONT
ASSOCIATED WITH THE POLAR TROUGH. THIS FRONT IS SLOWLY ADVANCING
EASTWARD ACROSS THE TENNESSEE VALLEY...AND EAST OF THE LOWER
MISSISSIPPI VALLEY. BUT...COLD AIR DAMMING TO THE LEE OF THE
SOUTHERN APPALACHIANS IS MAINTAINING A SHARP FRONTAL ZONE NEAR SOUTH
ATLANTIC COASTAL AREAS INTO SOUTHERN GEORGIA AND THE FLORIDA
PANHANDLE/ALABAMA BORDER AREA. THIS BOUNDARY IS EXPECTED TO REMAIN
QUASI-STATIONARY...AND THE FOCUS FOR THE MOST VIGOROUS CONVECTIVE
DEVELOPMENT THIS AFTERNOON/EVENING...AS IT PROVIDES STEEPER LIFT OF
A MOIST BOUNDARY LAYER WITH CAPE OF 500-1000 J/KG.
ALTHOUGH LOW-LEVEL HODOGRAPHS NEAR THE CONVECTIVE BAND ARE NOT
PARTICULARLY LARGE...STRONG DEEP LAYER SHEAR ON THE SOUTHERN FRINGE
OF THE PROMINENT SOUTHERN STREAM IS SUFFICIENT FOR SUPERCELLS. AN
ISOLATED TORNADO OR TWO IS POSSIBLE...BUT LOCALLY DAMAGING WIND
GUSTS AND HAIL APPEAR TO BE THE PRIMARY SEVERE THREATS.
MEANWHILE...ADDITIONAL VIGOROUS CONVECTIVE DEVELOPMENT IS ALSO
ONGOING NEAR AND EAST OF SOUTHEAST LOUISIANA COASTAL AREAS. THIS
APPEARS TO BE SUPPORTED BY FORCING ASSOCIATED WITH THE NEXT
SUBTROPICAL IMPULSE ...WHICH COULD CONTRIBUTING TO AN EXPANDING
CLUSTER OF STORMS ACROSS THE FLORIDA PANHANDLE LATER THIS AFTERNOON
AND EVENING. ALTHOUGH LATEST RUC GUIDANCE SUGGESTS THAT THE CORE OF
THE 30-40 KT WEST SOUTHWESTERLY LOW-LEVEL JET MAY ALREADY LIFTING
AWAY FROM SOUTHERN GEORGIA/NORTHERN FLORIDA...THE NAM/GFS AND ECMWF
HAVE INDICATED A LINGERING BELT OF MODERATELY STRONG LOW-LEVEL FLOW
ACROSS THIS REGION INTO THE EVENING HOURS. IF THESE PROGS ARE
CLOSER TO BEING CORRECT...BROADER SCALE DAMAGING WIND POTENTIAL MAY
ACCOMPANY THE EVOLVING CLUSTER BEFORE SPREADING EAST OF SOUTH
ATLANTIC COASTAL AREAS TONIGHT.
..KERR/SMITH.. 02/22/2008
CLICK TO GET WUUS01 PTSDY1 PRODUCT
NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 0100Z
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