MESOSCALE DISCUSSION 1462, AREAS AFFECTED...FAR EAST CENTRAL/SERN AND SRN MN...WEST CENTRAL WI...AND NRN IA CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY

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MESOSCALE DISCUSSION 1462 NWS STORM PREDICTION CENTER NORMAN OK 0602 PM CDT FRI JUL 13 2012 AREAS AFFECTED...FAR EAST CENTRAL/SERN AND SRN MN...WEST CENTRAL WI...AND NRN IA CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY VALID 132302Z - 140030Z PROBABILITY OF WATCH ISSUANCE...20 PERCENT SUMMARY...ISOLATED STRONG TO SEVERE STORMS WILL REMAIN POSSIBLE THROUGH THE EARLY EVENING ACROSS FAR EAST CENTRAL MN/WEST CENTRAL WI AND SWWD THROUGH SERN MN TO NRN IA. GIVEN RADAR TRENDS AND AVAILABLE DOWNSTREAM INSTABILITY...IT APPEARS THAT THIS ACTIVITY IS AT ITS PEAK...THOUGH ISOLATED HAIL APPROACHING SEVERE AND STRONGER WIND GUSTS WILL BE POSSIBLE. DISCUSSION...WATER VAPOR IMAGERY SHOWED A TROUGH MOVING SLOWLY EWD THROUGH THE UPPER MS VALLEY WITH AN EMBEDDED VORTICITY CENTER LOCATED OVER CENTRAL MN /NEAR 35 SW BRD/. STRONGEST MIDLEVEL FLOW ATTENDANT TO THIS SYSTEM EXTENDED FROM ERN SD INTO NRN IA. TRENDS IN REGIONAL RADAR IMAGERY SHOWED A BROKEN LINE OF STORMS EXTENDING FROM 50 S DLH THROUGH THE ERN AND SRN TWIN CITIES METRO TO PARTS OF SOUTH CENTRAL MN...WITH A SECOND AREA OF STORMS MOVING SEWD INTO NWRN IA. THE AIR MASS INVOF AND E-S OF THIS ACTIVITY IS MODERATELY UNSTABLE. THIS COMBINED WITH ASCENT ATTENDANT TO THE TROUGH AND VORTICITY CENTER WILL CONTINUE TO PROMOTE NEW TSTM DEVELOPMENT AS THE CONVECTIVE OUTFLOW BOUNDARY ADVANCES EWD INTO NWRN-WRN WI...SERN MN AND SWD INTO NRN IA. THUS FAR...MOST OF THE STORM REPORTS HAVE BEEN SUB-SEVERE...AND THIS IS LIKELY DUE TO WEAK DEEP LAYER SHEAR AND WEAK MIDLEVEL LAPSE RATES LIMITING THE SUSTENANCE OF THIS ACTIVITY. ALTHOUGH MODELS SUGGEST STORMS WILL PROGRESS EWD INTO WI AND SWD INTO IA THROUGH THE EVENING...STORMS SHOULD BE IN THEIR PEAK INTENSITIES FOR AT MOST ANOTHER 1-2 HOURS PRIOR TO BOUNDARY LAYER STABILIZATION WITH LOSS OF DAYTIME HEATING. MEANWHILE...STORMS THAT DEVELOP OVER SWRN MN INTO NWRN IA WILL HAVE A GREATER POTENTIAL FOR ORGANIZATION...GIVEN THE PROXIMITY TO STRONGER DEEP LAYER SHEAR. HOWEVER...THE PRESENCE OF WEAKER FORCING ALOFT SHOULD LIMIT STORM COVERAGE INTO NRN IA. ..PETERS/THOMPSON.. 07/13/2012 ATTN...WFO...DLH...ARX...MPX...DMX...FSD... LAT...LON 43519507 44299372 45219308 45849303 46029201 45879125 45129124 43839181 42969314 42889478 43139529 43519507