MESOSCALE DISCUSSION 1206 NWS STORM PREDICTION CENTER NORMAN OK 1140 AM CDT MON JUN 18 2012 AREAS AFFECTED...CNTRL/NERN WI...ERN UPPER MI CONCERNING...SEVERE POTENTIAL...WATCH LIKELY VALID 181640Z - 181845Z PROBABILITY OF WATCH ISSUANCE...80 PERCENT SUMMARY...SEVERE POTENTIAL WILL INCREASE WITH BOTH A CLUSTER OF TSTMS ALONG THE WI/MI BORDER AND ADDITIONAL TSTMS LIKELY FORMING ALONG A SW/NE-ORIENTED PRE-FRONTAL CONFLUENCE BAND. DEEP-LAYER SHEAR WILL BE HIGHLY FAVORABLE FOR INITIAL SUPERCELLS AND EVENTUAL UPSCALE GROWTH INTO AN MCS WITH BOWING SEGMENTS. DISCUSSION...CU HAS INCREASED ALONG A PRE-FRONTAL CONFLUENCE BAND SEEN IN VISIBLE SATELLITE IMAGERY FROM AROUND 30 S MSP TO 45 NE EAU IN THE WAKE OF PROBABLE ELEVATED CONVECTION ALONG THE WI/MI BORDER. AIR MASS IS STRONGLY DESTABILIZING IN BETWEEN THESE TWO FEATURES WITH MLCAPE NEARING 2000 J/KG AND WEAKENING MLCIN. GIVEN THE DEGREE OF INSTABILITY IN WI...IT APPEARS LIKELY THAT AT LEAST ISOLATED TSTMS SHOULD FORM ALONG THE CONFLUENCE BAND BY 18-19Z. WITH 50-60 KT EFFECTIVE SHEAR AND DEEP-LAYER FLOW LARGELY PARALLELING THE INITIATING BOUNDARY...INITIAL SUPERCELLS SHOULD QUICKLY GROW UPSCALE WITH EMBEDDED BOWING STRUCTURES. ALTHOUGH LOW-LEVEL FLOW IS LARGELY VEERED IN THE WARM SECTOR...AN ISOLATED TORNADO OR TWO IS POSSIBLE IN NERN WI WHERE FLOW SHOULD REMAIN MORE BACKED. OTHERWISE...SEVERE WIND/HAIL WILL BE THE PRIMARY RISKS. ..GRAMS/HART.. 06/18/2012 ATTN...WFO...MQT...GRB...MKX...DLH...ARX...MPX... LAT...LON 44869150 45448996 45928836 46028746 46048668 45668641 44848712 44238751 43738809 43528948 43609085 43809139 44349194 44869150
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