Posted by JAC on 3/28/2009, 9:24 am

To me, it looks like the area with the highest chance of a supercell and possibly tornado will be around: Huntsville AL, Dalton GA, Chattanooga TN, Knoxville TN. No big outbreaks today - thank goodness. SPC AC 281230 DAY 1 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 0730 AM CDT SAT MAR 28 2009 VALID 281300Z - 291200Z ...THERE IS A SLGT RISK OF SVR TSTMS ACROSS A LARGE PORTION OF THE OH/TN VLYS INTO THE SERN STATES... ...SYNOPSIS... INTENSE UPPER LEVEL LOW WHICH HAS BEEN SLOW TO MOVE OVER OK UP TO NOW WILL BEGIN TO EVOLVE INTO AN OPEN-WAVE AND EJECT RAPIDLY NEWD THROUGH TONIGHT INTO THE OH VALLEY. AS THIS OCCURS...SURFACE COLD FRONT WILL SURGE E-SEWD AND EXTEND ALONG THE CENTRAL APPALACHIANS INTO THE NERN GULF OF MEXICO BY THE END OF THE PERIOD. LARGE AREA OF ENHANCED MID AND UPPER LEVEL SSWLY WINDS ASSOCIATED WITH THIS SYSTEM WILL MAINTAIN ENHANCED DEEP LAYER SHEAR ACROSS NEARLY ALL OF THE SERN 1/4 OF THE CONUS. EXTENSIVE DEEP MOIST CONVECTION HAS BEEN PERSISTENT ALONG THE CENTRAL AND NERN GULF COAST REGION OVER THE PAST 24 HRS...WHICH HAS INHIBITED GULF MOISTURE RETURN AWAY FROM THE IMMEDIATE COAST THROUGH THE EARLY MORNING HOURS. HOWEVER...SSWLY LLJ IN EXCESS OF 60 KT EVIDENT ON MORNING VWP/S OVER THE NERN GULF COAST REGION WILL TRANSLATE ENEWD ACROSS MORE OF THE SOUTHEASTERN STATES TODAY. THIS SHOULD ALLOW EFFECTIVE WARM FRONT TO LIFT NWD/BECOME BETTER DEFINED FROM PORTIONS OF THE CENTRAL CAROLINAS INTO SRN/CENTRAL GA. LOCATION OF THIS FRONT/INSTABILITY GRADIENT WILL BE PARAMOUNT IN PINNING DOWN CORRIDOR OF MOST INTENSE SEVERE THREAT TODAY. IN ADDITION...INTENSE DEEP ASCENT AND STRONG HEIGHT FALLS ALOFT WILL ROTATE AROUND MAIN UPPER SYSTEM AND SUPPORT CONTINUED THREAT OF STRONG TO SEVERE THUNDERSTORMS AHEAD OF MAIN SURFACE COLD FRONT FROM THE MID SOUTH INTO THE TN/OH RIVER VALLEYS. THIS THREAT MAY EVOLVE IN THE FORM OF SUBSEQUENT BANDS OF MOIST CONVECTION WITH EACH BAND RACING NNEWD THROUGH THE PERIOD. IT REMAINS POSSIBLE THAT PORTIONS OF THE SRN APPALACHIANS MAY SEE A RELATIVE MINIMUM IN SEVERE THUNDERSTORMS AS COMPARED TO REGIONS TO THE NNW AND SSE. ...CENTRAL/NERN GULF COAST INTO THE SOUTHEAST/MID ATLANTIC... AREAS OF STRONG TO SEVERE THUNDERSTORMS HAVE BEEN PERSISTENT FROM THE MOUTH OF THE MS RIVER ACROSS SRN AL/FL PANHANDLE DURING THE EARLY MORNING AHEAD OF MAIN COLD FRONT. STRONG SLY LOW LEVEL FLOW AND AFOREMENTIONED SURFACE FRONT/INSTABILITY GRADIENT HAS LIFTED NWD PRECEEDING THIS ACTIVITY...ALLOWING INFLUX OF RICHER MOISTURE TO SPREAD INTO SWRN GA THROUGH 12Z. THIS TREND SHOULD PERSIST TODAY AND ALLOW AREA OF MARGINAL TO MODERATE MLCAPE TO EVOLVE FROM THE FL PANHANDLE INTO SRN GA/ERN CAROLINAS THROUGH THE DAY. EITHER THUNDERSTORMS WILL ORGANIZE/EVOLVE INTO A MORE COHERENT MCS AND LIFT ENEWD ACROSS THIS REGION TODAY...OR SERIAL SMALLER-SCALE SUPERCELLS/BOW ECHOES WILL CONTINUE TO EVOLVE OFF THE GULF AND/OR NEAR THE FRONT AND IMPACT THE REGION AS THEY RACE NEWD. EITHER CASE SUGGESTS THIS ZONE COULD BE QUITE ACTIVE WITH A MYRIAD OF SEVERE THREATS...AT LEAST THROUGH THE EARLY EVENING. NNEWD EXTENT OF SEVERE THREAT SHOULD BE TEMPERED AFTER DARK...HOWEVER AT LEAST ISOLATED SEVERE COULD ACCOMPANY STORMS INTO PORTIONS OF THE MID ATLANTIC DURING LATTER HALF OF PERIOD. ...MID SOUTH INTO THE TN/OH VLYS... A SEPARATE AREA OF SVR POTENTIAL WILL LIKELY DEVELOP ACROSS PORTIONS OF THE TN/OH VLYS DURING THE AFTN/EVE...WITH ONGOING STRONG TO MARGINALLY SEVERE STORMS FROM NERN AR INTO SRN MO. STRONGEST DCVA WILL TRANSLATE NEWD AWAY FROM THE RICH GULF MOISTURE SOURCE FARTHER SE. BUT...LINGERING 50S SFC DEW POINTS ARCING BACK ALONG THE CDFNT/SFC LOW INTO THE LWR OH VLY BENEATH STEEP MID-TROPOSPHERIC LAPSE RATES WILL CONTRIBUTE TO MLCAPES OF A FEW HUNDRED J PER KG. MODELS CONTINUE TO SUPPORT SCATTERED TSTM DEVELOPMENT AHEAD OF THE COLD FRONT THROUGH THE DAY AMIDST STRONG VERTICAL SHEAR....INCLUDING A FEW LOW-TOPPED SUPERCELLS. LARGE HAIL AND ISOLD DMGG WIND GUSTS WILL BE POSSIBLE. TORNADOES CANNOT BE RULED OUT...ALTHOUGH FORECAST SOUNDINGS INDICATE MUCH OF THIS ACTIVITY COULD REMAIN ELEVATED. SVR THREATS WILL DIMINISH WITH NE EXTENT AND AFTER SUNSET. ..EVANS/GARNER.. 03/28/2009