ZCZC SPCSWODY1 ALL ACUS01 KWNS 091238 SPC AC 091237 STORM PREDICTION CENTER...NWS/NCEP...NORMAN OK DAY 1 CONVECTIVE OUTLOOK...REF AWIPS GRAPHIC PGWE46 KWNS. VALID 091300Z - 101200Z NO SVR TSTM AREAS FCST. GEN TSTMS ARE FCST TO THE RIGHT OF A LINE FROM 15 SW 7R4 JAN 20 NNW LGC AHN 30 NNE CAE 25 E CRE ...CONT... PBI 10 NNW SRQ. EASTERN CANADIAN CLOSED LOW WILL SLOWLY PROGRESS EASTWARD DURING THIS FORECAST PERIOD...AS SEVERAL SHORT WAVES PROGRESS THROUGH CYCLONIC FLOW REGIME AROUND ITS PERIPHERY. ONE OF THESE SHORT WAVE TROUGHS IS NOW DIGGING INTO THE GREAT LAKES REGION...ACCOMPANIED BY AN INTENSE /130+ KT/ POLAR JET STREAK. MODELS SUGGEST SHORT WAVE/ JET STREAK IS BOTTOMING OUT...AND WILL TURN EASTWARD ACROSS NEW ENGLAND AND THE NORTHERN MID ATLANTIC COAST STATES LATER THIS MORNING AND AFTERNOON. AS THIS OCCURS...SHORT WAVE TROUGH EMBEDDED WITHIN THE SUBTROPICAL WESTERLIES OVER THE CENTRAL GULF COAST STATES IS PROGGED TO WEAKEN AND ACCELERATE EASTWARD OFF THE SOUTH ATLANTIC COAST. ANOTHER NORTHERN BRANCH SHORT WAVE TROUGH IS PROGGED TO AMPLIFY AND DIG ACROSS THE GREAT LAKES REGION TONIGHT... WHILE SUBTROPICAL JET BECOMES INCREASINGLY ANTICYCLONIC ACROSS THE GULF STATES. IN RESPONSE TO EVOLVING UPPER FLOW PATTERN...POLAR FRONT WILL SLOWLY ADVANCE SOUTHWARD THROUGH THE SOUTH ATLANTIC AND GULF COAST STATES TODAY...WHILE ANOTHER WEAKER FRONT...ASSOCIATED WITH THE SUBTROPICAL JET...BECOMES QUASI-STATIONARY ACROSS THE NORTH CENTRAL FLORIDA PENINSULA. VIGOROUS CONVECTION IS ONGOING ALONG THE SOUTHERN FRONTAL ZONE...AND THIS BOUNDARY WILL BE FOCUS FOR PRIMARY THUNDERSTORM ACTIVITY DURING THIS FORECAST PERIOD. ...FLORIDA... LOW-LEVEL WARM ADVECTION/ISENTROPIC LIFT ALONG/NORTH OF SURFACE FRONT IS SUPPORTING ONGOING CONVECTION. FRONT EXTENDS FROM THE NORTH CENTRAL GULF COAST THROUGH THE FLORIDA BIG BEND INTO NORTHERN FLORIDA...WITH LARGE-SCALE UPWARD VERTICAL MOTION FIELD ENHANCED BY STRONGEST MID/UPPER FORCING ACROSS SOUTHERN ALABAMA AND THE WESTERN FLORIDA PANHANDLE AT 12Z. THIS FORCING...ASSOCIATED WITH WEAKENING MID/UPPER TROUGH...IS PROGGED TO RAPIDLY SPREAD ACROSS NORTHERN FLORIDA...THROUGH THE JACKSONVILLE AREA BY 18Z. INSTABILITY FOR PARCELS LIFTED ABOVE SHALLOW SURFACE INVERSION NORTH OF SURFACE BOUNDARY HAS BEEN SUFFICIENT TO SUPPORT A FEW VIGOROUS UPDRAFTS WITH ISOLATED LARGE HAIL...AND THIS WILL LIKELY REMAIN THE CASE THROUGH THE MORNING HOURS. MEANWHILE...SURFACE HEATING ALONG/JUST SOUTH OF FRONT WILL CONTRIBUTE TO WEAK TO MODERATE SURFACE-BASED DESTABILIZATION...WHICH MAY SUPPORT INTENSIFYING CLUSTER OF STORMS NEAR WAVE ALONG BOUNDARY... NEAR/NORTH OF GAINESVILLE BY MID MORNING. MODELS SUGGEST SOME STRENGTHENING OF LOW-LEVEL FLOW ACROSS NORTHERN FLORIDA DURING THIS TIME...WITH 850 JET INCREASING TO NEAR 30 KTS. THIS WILL SUPPORT AT LEAST A MINIMAL THREAT FOR DAMAGING WIND GUSTS APPROACHING OR BRIEFLY EXCEEDING 50 KT AS ACTIVITY PROGRESSES NEAR/ SOUTH OF JACKSONVILLE BY EARLY AFTERNOON. AS SURFACE WAVE PROGRESSES OFFSHORE...THUNDERSTORM ACTIVITY ALONG TRAILING CONFLUENT BAND WILL GRADUALLY SPREAD SOUTHWARD INTO THE NORTH CENTRAL PENINSULA DURING THE AFTERNOON HOURS...AND MAY CONTINUE TO BE ACCOMPANIED BY GUSTY/ISOLATED DAMAGING SURFACE WINDS. ...REMAINDER OF THE SOUTHEASTERN STATES... POLAR FRONT MAY BECOME FOCUS FOR ADDITIONAL CONVECTIVE DEVELOPMENT LATER TODAY FROM SOUTHERN MISSISSIPPI AND ALABAMA INTO CENTRAL GEORGIA AND SOUTH CAROLINA. ALTHOUGH SURFACE HEATING MAY BE SOMEWHAT LIMITED...LOW-LEVEL MOISTURE APPEARS SUFFICIENT TO SUPPORT AT LEAST WEAK INSTABILITY AND WIDELY SCATTERED THUNDERSTORMS BENEATH CYCLONIC MID-LEVEL FLOW...MOSTLY NEAR/SHORTLY AFTER PEAK HEATING THIS AFTERNOON. ..KERR.. 03/09/03 NNNN |