The SPC is forecasting ...significant severe thunderstorms expected over parts of the gulf coast states this afternoon and tonight.... Please read the latest public statement about this event.
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SPC AC 181615 DAY 1 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 1015 AM CST WED FEB 18 2009 VALID 181630Z - 191200Z ...THERE IS A MDT RISK OF SVR TSTMS OVER PARTS OF LA...MS...AL...GA AND THE FL PANHANDLE... ...THERE IS A SLGT RISK OF SVR TSTMS SURROUNDING THE MDT RISK AREA FROM LA INTO PARTS OF TN...KY...GA..NRN FL AND THE S ATLANTIC CST... ...SYNOPSIS... FAST WSW FLOW WILL PREVAIL OVER THE S CNTRL AND SE U.S. TODAY/ TONIGHT...ON SRN FRINGE OF NRN STREAM TROUGH AMPLIFYING SE ACROSS THE UPR GRT LKS/MID MS VLY. S OF THE TROUGH...EXISTING SRN BRANCH JET...NOW EXTENDING FROM NM TO AR...WILL DEVELOP ESEWD. THIS WILL ENHANCE MID LVL FLOW OVER THE SERN STATES TODAY...WITH MORE SUBSTANTIAL STRENGTHENING EXPECTED TONIGHT/EARLY THURSDAY. AT THE SFC...LOW ASSOCIATED WITH NRN STREAM IMPULSE SHOULD TRACK NE TO NEAR LK HURON THIS EVE AS TRAILING COLD FRONT CONSOLIDATES AND ACCELERATES SE ACROSS THE OH...TN...AND LWR MS VLYS. LARGE SURFACE LOW CONTINUES TO DEEPEN AS IT TRACKS NEWD ACROSS THE GREAT LAKES INTO SWRN ONTARIO WITH A TRAILING COLD FRONT SWEEPS SEWD THRU GULF STATES THIS AFTERNOON AND TONIGHT. AREA OF CONFLUENCE AHEAD OF COLD FRONT FROM WRN KY SWWD INTO NRN MS PROVIDING LOW LEVEL CONVERGENCE IN THE FAST WESTERLY FLOW. ...TN VLY TO CNTRL GULF CST/GA/N FL... REF MCD #119 POTENTIAL EXISTS FOR SIGNIFICANT SVR STORMS THIS AFTN THROUGH EARLY THURSDAY AHEAD OF AFOREMENTIONED COLD FRONT AND CONFLUENCE ZONE. LOW LEVEL MOISTURE CONTINUES TO SPREAD RAPIDLY NEWD THRU GULF STATES INTO TN VALLEY AHEAD OF THE COLD FRONT. VERY STRONG WESTERLIES OVERLAY THE RETURNING MOISTURE WHICH COUPLED WITH RELATIVELY COLD MID LEVEL TEMPS AND STEEP LAPSE RATES WILL SUPPORT SURFACE BASED STORM DEVELOPMENT ALONG AND AHEAD OF CONFLUENCE ZONE. WITH MLCAPES RISING TO 1000 J/KG WITH HEATING SPREADING EWD ACROSS MS INTO AL COUPLED WITH STRONG SHEAR...SEVERE THUNDERSTORMS SHOULD INCREASE IN NUMBER AND INTENSITY ACROSS THE TN VALLEY AND EXTENDING FURTHER S THRU ERN MS AND AL THIS AFTERNOON. WHILE HAIL/WIND WILL INITIALLY BE THE CONCERN GIVEN THE LIMITED INSTABILITY...INCREASING THREAT OF SUPERCELLS AND TORNADOES WILL DEVELOP AS HEATING/DESTABILIZATION SPREAD EWD DURING THE AFTERNOON ALONG WITH THE VERY STRONG SHEAR PROFILES CURRENTLY IN PLACE ACROSS THE GULF STATES AND TN VALLEY. AS THE COLD FRONT CATCHES UP WITH ONGOING STORMS LATER THIS AFTERNOON A MORE LINEAR MODE IS LIKELY INCREASING THE THREAT OF AN ORGANIZED SQUALL LINE AND WIND DAMAGE. IN ADDITION ANY STORM AHEAD OF THE SQUALL LINE WILL BE POTENTIALLY A SUPERCELL. GIVEN THE VERY STRONG SHEAR...TORNADOS ARE POSSIBLE WITH ANY SUPERCELL WITH POSSIBLY AN ISOLATED STRONG TORNADO FROM CENTRAL AL S AND SE INTO SWRN GA/FL PANHANDLE THIS EVENING. ALTHOUGH THE STORMS ALONG THE COLD FRONT SHOULD DIMINISH UPON ENCOUNTERING LESS FAVORABLE LOW LVL THERMODYNAMIC ENVIRONMENT IN THE SRN/CNTRL APPALACHIANS...THOSE THAT FORM ALONG PRE-FRONTAL CONFLUENCE BAND COULD STRENGTHEN THROUGH THE EVE AS /1/ MORE SUBSTANTIAL HEIGHT FALLS OVERSPREAD REGION AND /2/ LOW LVL MOISTURE INFLOW CONTINUES TO INCREASE ALONG THE CNTRL/ERN GULF CST. SOME OF THE STORMS COULD MOVE/DEVELOP E ACROSS CNTRL/SRN GA AND N FL GIVEN DEEP UNIDIRECTIONAL FLOW. ..HALES.. 02/18/2009 CLICK TO GET WUUS01 PTSDY1 PRODUCT NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 2000Z