The SPC is forecasting ...severe thunderstorms expected from the central/southern plains to the mid mississippi valley later today and tonight.... Please read the latest public statement about this event.
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SPC AC 131612 DAY 1 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 1112 AM CDT WED MAY 13 2009 VALID 131630Z - 141200Z ...THERE IS A MDT RISK OF SVR TSTMS THIS AFTERNOON AND EVENING OVER PARTS OF OK...SOUTHEAST KS...NORTHWEST AR...MUCH OF MO AND MUCH OF IL... ...THERE IS A SLGT RISK OF SVR TSTMS FROM PARTS OF THE CENTRAL/SOUTHERN PLAINS INTO THE MID MISSISSIPPI VALLEY...... ...SYNOPSIS... VIGOROUS TROUGH AND STRONG POLAR JET MAX MOVES EWD FROM NRN PLAINS TO UPPER GREAT LAKES LATER TONIGHT...WITH GREATEST CONVECTIVE POTENTIAL REMAINING ALONG THE SRN PERIPHERY OF THIS SYSTEM WHERE THE RESERVOIR OF MOIST/UNSTABLE AIR MASS RESIDES. COLD FRONT EXTENDS FROM THE DEEP LOW WRN ONTARIO SWWD THRU UPPER MS VALLEY...CENTRAL KS TO NRN TX PANHANDLE THIS AM. VERY STRONG SWLY LOW LEVEL JET AOA 60KT FROM SRN PLAINS INTO LOWER MO VALLEY CHARACTERIZED BY A PRONOUNCED EML ATOP A VERY MOIST BUT RELATIVELY SHALLOW MOIST LAYER. STRONG ISENTROPIC ASCENT UNDERWAY ACROSS MID MS VALLEY WITH CURRENT ELEVATED THUNDERSTORMS EXPECTED TO CONTINUE AND LIKELY BECOME MORE INTENSE THRU THE AFTERNOON. ...MID MS VALLEY/LOWER MO VALLEY... PERSISTENT ELEVATED THUNDERSTORMS MID MS INTO LOWER OH VALLEYS WILL TRANSITION INTO A MORE SURFACE BASED SUPERCELL THREAT BY MID AFTERNOON AS TEMPERATURES CLIMB ALONG WITH DEWPOINTS TO THE S AND W ACROSS MO INTO SERN KS. WITH MID LEVEL LAPSE RATES IN EXCESS OF 8C/KM AND DEWPOINTS RISING THRU THE 60S F...MLCAPES UPWARD OF 2500 J/KG WILL DEVELOP WITH WEAKENING CINH BY MID AFTERNOON UPSTREAM FROM THE ONGOING ELEVATED STORMS. WHILE DEEP LAYER SHEAR OF 40KT IS NOT PARTICULARLY STRONG FOR TORNADIC SUPERCELLS...THE ENHANCED LOW LEVEL SHEAR VICINITY OF CONVECTIVE BOUNDARIES WILL LOCALLY ENLARGE HODOGRAPHS AND BE QUITE FAVORABLE FOR AT LEAST A COUPLE SUPERCELLS CAPABLE OF PRODUCING STRONG TORNADOES BY LATER THIS AFTERNOON/EVENING GIVEN THE EXPECTED INSTABILITY. IN ADDITION VERY LARGE HAIL SHOULD OCCUR WITH ANY SUPERCELL AND WIND DAMAGE WILL BECOME MORE OF A THREAT AS CONVECTION TRANSITIONS INTO MORE OF A LINEAR MODE BY THIS EVENING. ANOTHER FACTOR IN TODAYS CONVECTIVE SCENARIO WILL LIKELY BY THE MCV NOW INTO SWRN MO. AS AIR MASS DESTABILIZES ACROSS SRN MO IN ADVANCE OF THIS FEATURE A SEVERE THUNDERSTORM THREAT WOULD LIKELY DEVELOP BY MID AFTERNOON. ...SRN PLAINS... STRONG CAP IN PLACE AHEAD OF SEWD ADVANCING COLD FRONT. BY LATER THIS AFTERNOON THE FRONT WILL BE A PRIMARY FOCUS OF RAPID DEVELOPMENT OF SEVERE THUNDERSTORMS SWRN MO/SERN KS INTO NRN OK WHERE A VERY TO EXTREMELY UNSTABLE AIR MASS WILL BE IN PLACE. AS SFC TEMPS ACROSS OK WARM TO AOA 90F WITH DEWPOINTS WELL INTO THE 60S...MLCAPES WILL CLIMB TO AS HIGH AS 4000 J/KG. ONCE THE COMBINATION OF FRONTAL FORCING AND HEATING IS SUFFICIENT TO WEAKEN CAP...SEVERE THUNDERSTORMS INCLUDING SUPERCELLS WILL DEVELOP RAPIDLY. WITH THE THREAT AREA LOCATED ON THE SRN FRINGE OF THE STRONG POLAR JET PASSING BY TO THE N...DEEP LAYER SHEAR WILL BE A LIMITING FACTOR FOR TORNADOS. HOWEVER GIVEN THE AMOUNT OF INSTABILITY AND LOCALLY ENHANCED LOW LEVEL SHEAR BY EVENING AFTER STORMS ARE UNDERWAY...AT LEAST AN ISOLATED TORNADO THREAT IS EXPECTED. HOWEVER VERY LARGE HAIL IS GOING TO BE A PRIMARY CONCERN ALONG WITH DAMAGING DOWNBURST WINDS WITH ANY SUPERCELL THAT DEVELOPS IN THIS ENVIRONMENT. A LINEAR MCS WILL THEN DEVELOP SEWD ACROSS MUCH OF OK INTO NRN AR TONIGHT WITH A CONTINUED THREAT OF AT LEAST DAMAGING WINDS CONTINUING. ..HALES/GARNER.. 05/13/2009 CLICK TO GET WUUS01 PTSDY1 PRODUCT NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 2000Z