WATCH POSSIBLE FOR PORTIONS WI...EXTREME NRN IL...WRN LM

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MESOSCALE DISCUSSION 1601 NWS STORM PREDICTION CENTER NORMAN OK 1209 PM CDT THU JUL 26 2012 AREAS AFFECTED...PORTIONS WI...EXTREME NRN IL...WRN LM. CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE VALID 261709Z - 261915Z PROBABILITY OF WATCH ISSUANCE...40 PERCENT SUMMARY...TSTMS FCST TO INCREASE IN COVERAGE AND INTENSIFY OVER WRN PORTIONS DISCUSSION AREA AND MOVE ESEWD TO SEWD...WITH POTENTIAL FOR LARGE HAIL AND OCNL DAMAGING GUSTS. DISCUSSION...16Z SFC MESOANALYSIS SHOWS OCCLUSION TRIPLE POINT OVER N-CENTRAL/NWRN WI W RHI...WITH DIFFUSE COLD FRONT SSWWD ACROSS EXTREME SERN MN. WARM FRONT WAS DRAWN FROM TRIPLE POINT SEWD ACROSS CENTRAL LM THEN EWD AND QUASISTATIONARY OVER CENTRAL LOWER MI. WARM FRONT SHOULD DRIFT NEWD WHILE COLD FRONT PROCEEDS SEWD 15-20 KT. VIS IMAGERY SHOWS WELL-DEFINED WRN LOW-CLOUD EDGE NEAR OR JUST AHEAD OF SFC COLD FRONT...WITH THICKEST CU/TCU AND A FEW SMALL CB OVER SFC MOIST AXIS. THAT CORRESPONDS TO AREA OF HIGHEST BUOYANCY AND WEAKEST CAPPING...MLCAPE RANGING FROM NEARLY 2000 J/KG OVER SWRN WI TO AROUND 500 J/KG ALONG WARM FRONT. CONVERGENCE SHOULD REMAIN WEAK ALONG/AHEAD OF COLD FRONT...INDICATING 1. GREATEST POTENTIAL FOR ADDITIONAL DEVELOPMENT TO ITS E NEAR MOIST AXIS AND 2. THREAT EVOLUTION SHOULD BE GRADUAL...NOT EXPLOSIVE IN NATURE. AIR MASS SHOULD CONTINUE TO DESTABILIZE IN WARM SECTOR...WITH DIABATIC HEATING AND UPPER 60S TO LOW 70S F SFC DEW POINTS BOOSTING MLCAPE ANOTHER 500-1000 J/KG ABOVE PRESENT VALUES THROUGH MID-AFTN. STRONGEST DEEP-LAYER SHEAR WILL BE OVER SRN WI...PERHAPS SHIFTING SWD TOWARD IL BORDER WITH TIME...IN STEP WITH MID-UPPER LEVEL JET AXIS. EFFECTIVE SHEAR MAGNITUDES 40-50 KT SUPPORT POTENTIAL FOR A FEW SUPERCELLS...ENHANCING HAIL/WIND RISK ON STORM SCALE. ..EDWARDS/HART.. 07/26/2012