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| Probability of severe weather within 25 miles of a point. Hatched Area: 10% or greater probability of significant severe within 25 miles of a point. |
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SPC AC 200550 DAY 2 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 1250 AM CDT TUE AUG 20 2013 VALID 211200Z - 221200Z ...THERE IS A SLGT RISK OF SVR TSTMS FOR THE UPPER MIDWEST/UPPER MS VALLEY... ...SYNOPSIS... AN UPPER-LEVEL SHORTWAVE TROUGH WILL MOVE FROM THE CANADIAN PRAIRIE PROVINCES TO THE UPPER GREAT LAKES REGION DURING THE D2 PERIOD. AS THIS OCCURS...ASSOCIATED SURFACE COLD FRONT WILL MOVE SWD ACROSS THE UPPER MS VALLEY AND NRN PLAINS...WITH ITS WRN EXTENSION EVENTUALLY STALLING OVER THE CNTRL HIGH PLAINS. FARTHER W...AN UPPER-LEVEL CLOSED LOW WILL GRADUALLY BEGIN TO SHIFT FROM THE CNTRL CA COAST TOWARD NRN CA. ...UPPER MIDWEST/UPPER MS VALLEY... A COLD FRONT WILL MOVE SWD ACROSS THE UPPER MIDWEST/UPPER MS VALLEY ON WEDNESDAY. DEWPOINTS ARE FORECAST TO RESIDE IN THE UPPER 60S ALONG/AHEAD OF THE FRONT...WHICH WILL SUPPORT MLCAPE VALUES FROM 2000-3000 J/KG AS THE BOUNDARY LAYER WARMS/DESTABILIZES. GLANCING INFLUENCE OF LARGE-SCALE ASCENT ASSOCIATED WITH A SHORTWAVE TROUGH OVER CANADA COMBINED WITH FRONTAL CONVERGENCE/ASCENT IS EXPECTED TO YIELD SCATTERED THUNDERSTORM DEVELOPMENT DURING THE AFTERNOON/EVENING. DEEP-LAYER WLY WINDS FROM 20-30 KT WILL BE SUFFICIENT FOR MULTICELL CLUSTERS AND LINE SEGMENTS POSING A RISK FOR LARGE HAIL AND DAMAGING WINDS. ...PORTIONS OF THE CNTRL/NRN HIGH PLAINS... POST FRONTAL UPSLOPE WINDS WILL ADVECT DEWPOINTS IN THE 50S WWD INTO THE CNTRL/NRN HIGH PLAINS BY WEDNESDAY AFTERNOON. THIS MOISTURE COMBINED WITH DAYTIME HEATING AND STEEP MIDLEVEL LAPSE RATES WILL SUPPORT WEAK TO MODERATE CAPE OVER THE AREA. AS A RESULT...ISOLATED THUNDERSTORM DEVELOPMENT WILL BE POSSIBLE OVER ELEVATED HEATING SOURCES AND ALSO ALONG A FRONT LOCATED OVER NERN CO/SWRN NEB. LOW-LEVEL ELYS SURMOUNTED BY MIDLEVEL WLYS WILL YIELD SHEAR PROFILES SUFFICIENT FOR A FEW SHORT-LIVED SUPERCELLS AND AN ISOLATED THREAT FOR LARGE HAIL. ...NRN CA...NWRN NV...SRN ORE... DEWPOINTS IN THE 40S AND 50S COMBINED WITH STRONG BOUNDARY LAYER DESTABILIZATION AND STEEP MIDLEVEL LAPSE RATES WILL SUPPORT MUCAPE VALUES FROM 500-1000 J/KG DURING THE AFTERNOON AND EVENING. THIS WILL SUPPORT SCATTERED THUNDERSTORM DEVELOPMENT AS UPPER DIVERGENCE AND ASCENT SPREAD ACROSS THE AREA AHEAD OF A CLOSED LOW POSITIONED OVER THE CA COAST. FLOW ALOFT WILL RANGE FROM 30-50 KT OUT OF THE SSE...WHICH MAY YIELD SUFFICIENT DEEP-LAYER SHEAR FOR A FEW ORGANIZED THUNDERSTORMS POSING A THREAT FOR HAIL/WIND GUSTS NEAR SEVERE LEVELS. ..GARNER.. 08/20/2013 CLICK TO GET WUUS02 PTSDY2 PRODUCT NOTE: THE NEXT DAY 2 OUTLOOK IS SCHEDULED BY 1730Z |