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 130600 DAY 1 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 0100 AM CDT WED MAY 13 2009 VALID 131200Z - 141200Z ...THERE IS A MDT RISK OF SVR TSTMS FROM THE MIDDLE MISSISSIPPI VALLEY TO THE SOUTH CENTRAL PLAINS... ...THERE IS A SLGT RISK OF SVR TSTMS MUCH OF THE MIDWEST TO SOUTHERN PLAINS... ...SYNOPSIS... ON THE LARGE SCALE...PRIMARY IMPETUS FOR DEEP CONVECTIVE POTENTIAL ACROSS THE CENTRAL STATES TODAY WILL BE TIED TO A POTENT UPPER TROUGH WHICH WILL CROSS THE NORTHERN PLAINS TODAY...AND REACH THE UPPER MISSISSIPPI VALLEY/WESTERN GREAT LAKES LATE TONIGHT AS IT BEGINS TO TAKE ON MORE OF A NEGATIVE TILT. AHEAD OF THIS SYSTEM...A RATHER MOIST AIRMASS WILL CONTINUE TO QUICKLY SURGE NORTHEASTWARD INTO THE MIDWEST AHEAD OF AN EAST-SOUTHEAST MOVING COLD FRONT ACROSS THE MIDWEST/SOUTH CENTRAL PLAINS. ...MIDWEST TO SOUTH CENTRAL PLAINS... INITIALLY...ON THE NOSE OF A RATHER STRONG SOUTHWESTERLY LOW LEVEL JET AND EASTERN FRINGE OF A PLAINS ELEVATED MIXED LAYER...SCATTERED TO NUMEROUS TSTMS ARE LIKELY TO BE ONGOING AT THE BEGINNING OF THE PERIOD ACROSS THE MIDWEST...INCLUDING PORTIONS OF IA/MO/IL/INDIANA. AT LEAST SOME OF THESE ELEVATED TSTMS WILL BE CAPABLE OF SEVERE HAIL THROUGH THE MORNING. ALTHOUGH SOME QUESTIONS EXIST REGARDING THE TIMING/DEGREE OF DIURNAL DESTABILIZATION WITH NORTHEASTWARD EXTENT ACROSS THE MIDDLE/UPPER MISSISSIPPI VALLEY IN THE WAKE OF EARLY DAY ACTIVITY...RAPID DESTABILIZATION IS EXPECTED TO OCCUR FROM THE SOUTHWEST...WITHIN A NARROW PRE-COLD FRONTAL WARM/UNSTABLE SECTOR ACROSS MO/SOUTHEAST IA INTO ADJACENT IL. PROVIDED SUFFICIENT DESTABILIZATION THROUGH THE AFTERNOON/EARLY EVENING...STRONG/SEVERE TSTMS SHOULD QUICKLY DEVELOP...WITH A MIXED MODE OF SUPERCELLS/BOWS POSSIBLE BENEATH 50 KT MID LEVEL FLOW. ASIDE FROM SEVERE HAIL...TORNADOES WILL BE POSSIBLE GIVEN STRONG 40-50 KT FLOW IN THE LOWEST 1 KM AND AMPLE LOW LEVEL SRH. THIS THREAT COULD BE HEIGHTENED IN VICINITY OF WARM FRONT AND/OR ANY REMNANT MODIFIED OUTFLOW ACROSS THE MIDDLE MISSISSIPI VALLEY INCLUDING PORTIONS OF MO/SOUTHEAST IA INTO IL. OTHERWISE...DAMAGING WIND POTENTIAL MAY ULTIMATELY INCREASE THROUGH THE EVENING AS STORMS CONGEAL/RACE EASTWARD ACROSS THE MIDWEST. FARTHER SOUTHWEST...TSTMS SHOULD DEVELOP LATE THIS AFTERNOON/EARLY EVENING ALONG/JUST BEHIND THE SOUTHEASTWARD ADVANCING SURFACE COLD FRONT FROM MO/SOUTHEAST KS INTO OK...AND PERHAPS IN VICINITY OF THE DEEPLY MIXED AIRMASS IN CLOSE PROXIMITY TO THE SURFACE LOW/DRYLINE TRIPLE POINT NEAR THE WESTERN OK/TX PANHANDLE BORDER. EVEN WITH WEAKER MID LEVEL FLOW AT THIS LATITUDE...VERY STEEP MID LAPSE RATES/VEERING WIND PROFILES WILL BE FAVORABLE FOR LARGE/POTENTIALLY SOME SIGNIFICANT HAIL WITH SUPERCELLS. A FEW TORNADOES MAY BE POSSIBLE...ALONG WITH DAMAGING WINDS GIVEN THE STEEP LAPSE RATE ENVIRONMENT. AS AN UPSWING IN TSTM COVERAGE CONTINUES THROUGH THE EVENING ALONG THE FRONTAL ZONE...AND A SOUTH-SOUTHWESTERLY LOW LEVEL JET NOCTURNALLY INCREASES ACROSS TX...THERE IS SOME POTENTIAL THAT THESE TSTMS COULD CONSOLIDATE AND GROW UPSCALE INTO A FORWARD PROPAGATING MCS...WITH HEIGHTENED DAMAGING WIND POTENTIAL ACROSS OK/AR INTO THE ADJACENT ARKLATEX VICINITY. ...CENTRAL GULF COAST STATES AND FL... MAINLY ISOLATED SEVERE TSTMS WILL BE POSSIBLE THIS AFTERNOON/EARLY EVENING ALONG THE RESIDUAL FRONTAL ZONE AND MOISTURE/INSTABILITY AXIS ACROSS THE GULF COAST STATES...AS WELL AS THE FL SEA BREEZE. ..GUYER/JEWELL.. 05/13/2009 CLICK TO GET WUUS01 PTSDY1 PRODUCT NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1300Z