The SPC is forecasting ...severe thunderstorms expected over parts of the northern plains and upper mississippi valley this afternoon and tonight... the nws storm prediction center in norman ok is forecasting the development of tornadoes...large hail and damaging winds over portions of the northern plains and upper mississippi valley this afternoon and tonight. the areas most likely to experience this activity include southern minnesota eastern south dakota western wisconsin surrounding the moderate risk area...there is a slight risk of severe thunderstorms across most of the dakotas...nebraska.... Please read the latest public statement about this event.
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SPC AC 241958 DAY 1 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 0258 PM CDT THU AUG 24 2006 VALID 242000Z - 251200Z ...THERE IS A MDT RISK OF SVR TSTMS THIS AFTERNOON AND TONIGHT OVER PARTS OF NERN SD...SERN ND...CNTRL/SRN MN AND W-CNTRL WI... ...THERE IS A SLGT RISK OF SVR TSTMS FROM THE DAKOTAS INTO PARTS OF THE UPPER GREAT LAKES... ...DAKOTAS INTO THE UPPER GREAT LAKES... COMPLEX SCENARIO IS EVOLVING TODAY ACROSS THE REGION IN ADVANCE OF STRONG SHORT WAVE TROUGH TRANSLATING EWD THROUGH WRN/CNTRL ND. WATER VAPOR IMAGERY SUGGESTS THAT A LEAD IMPULSE IS CURRENTLY SHIFTING EWD THROUGH CNTRL/ERN SD WHICH IS LIKELY SUPPORTING THE ONGOING STORMS FROM FAR NERN SD INTO CNTRL MN. IN THE LOW-LEVELS...PRIMARY SURFACE LOW APPEARS TO BE W OF MBG WITH ATTENDANT WARM FRONT EXTENDING SEWD TO NEAR HON AND THEN ACROSS SRN MN TO NEAR THE WI/IL BORDER. A SECONDARY SURFACE LOW WAS ANALYZED ALONG THIS BOUNDARY N OR NE OF FSD WITH A TRAILING PRE-FRONTAL TROUGH STRETCHING SWWD FROM THIS LOW INTO CNTRL NEB. MEANWHILE...COLD FRONT /CURRENTLY MASKED BY ADIABATIC DOWNSLOPE WARMING/ EXTENDED FROM NEAR MOT TO PHP INTO THE NEB PNHDL. THUS FAR TODAY...PRIMARY SEVERE IN THE FORM OF ELEVATED SUPERCELLS PRODUCING LARGE /AND AT TIMES SIGNIFICANT/ HAIL HAS PERSISTED FROM CNTRL MN INTO SRN WI IN ASSOCIATION WITH LOW-LEVEL WAA/ISENTROPIC ASCENT REGIME N OF WARM FRONT. BOTH 12Z AND 18Z REGIONAL SOUNDINGS INDICATE THAT INFLOW PARCEL SOURCE REGION OVER THE MID MO VALLEY INTO SRN MN REMAINS MODERATE TO STRONGLY UNSTABLE WITH MUCAPES OF 2500-4500 J/KG. STRENGTHENING SWLY LLJ THIS AFTERNOON AND TONIGHT SHOULD MAINTAIN CLUSTERS OF ELEVATED SUPERCELLS TO THE N OF SURFACE BOUNDARY WITH VERY LARGE HAIL BEING THE MAIN SEVERE THREAT. OTHER SURFACE-BASED STORMS WILL BECOME INCREASINGLY LIKELY LATE THIS AFTERNOON INTO EVENING FROM SERN SD EWD ACROSS SRN MN NEAR AND E OF TRIPLE POINT ASSOCIATED WITH SECONDARY SURFACE LOW. MODERATELY STRONG LOW-LEVEL SHEAR /0-1 KM SRH OF 100-200 M2/S2/ COUPLED WITH THE MODERATE TO STRONG INSTABILITY AND 40-50 KTS OF EFFECTIVE BULK SHEAR INDICATE THE POTENTIAL FOR SUPERCELLS CAPABLE OF A FEW TORNADOES...LARGE HAIL AND DAMAGING WINDS SHOULD STORMS DEVELOP AND BECOME SUSTAINED. FARTHER DOWNSTREAM...TSTM COMPLEX OVER SRN WI WILL POSE A DAMAGING WIND/LARGE HAIL THREAT AS IT CONTINUES SEWD ALONG BAROCLINIC ZONE ACROSS SERN WI/NERN IL. MEANWHILE...A LARGE CLUSTER OF TSTMS INCLUDING EMBEDDED SUPERCELLS CONTINUES TO INCREASE IN COVERAGE AND INTENSITY THIS AFTERNOON OVER PORTIONS OF WRN AND CNTRL ND...IMMEDIATELY AHEAD OF SHORT WAVE TROUGH. VISIBLE SATELLITE IMAGERY AND SURFACE OBSERVATIONS INDICATE THAT AIR MASS IS RECOVERING AHEAD OF THIS ACTIVITY OVER N-CNTRL SD INTO S-CNTRL ND WHERE STRONGER DIABATIC HEATING HAS ALLOWED TEMPERATURES TO WARM INTO THE 80S...SUPPORTING MLCAPES OF 1500-3000 J/KG. WHILE THERE HAS BEEN SOME TENDENCY FOR STORMS TO EVOLVE INTO A MORE LINEAR CONFIGURATION...POTENTIAL STILL EXISTS FOR MORE DISCRETE SUPERCELLS ALONG SRN PORTION OF COMPLEX NEAR SURFACE LOW AND ATTENDANT WARM FRONT WITH A THREAT OF A FEW TORNADOES AS WELL AS LARGE HAIL AND DAMAGING WINDS. THERE IS SOME UNCERTAINTY AS TO HOW FAR S STORMS WILL FORM INTO CNTRL SD OWING TO CLOSE PROXIMITY OF LEAD SHORT WAVE TROUGH OVER ERN SD. LATEST VISIBLE IMAGERY DOES INDICATE DEEPENING CUMULUS ALONG COLD FRONT SW OF MBG AND SSE PHP. SHOULD STORMS DEVELOP AND BECOME SUSTAINED THE COMBINATION OF MODERATE TO STRONG INSTABILITY AND MODERATELY STRONG VERTICAL SHEAR WILL BE SUPPORTIVE OF SUPERCELLS AND BOWING STRUCTURES CAPABLE OF LARGE HAIL...DAMAGING WINDS AND PERHAPS A COUPLE OF TORNADOES. ..MEAD.. 08/24/2006 CLICK TO GET WUUS01 PTSDY1 PRODUCT NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 0100Z