SPC 1200Z Day 1 Outlook
DAY 1 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 1253 AM CDT WED JUL 10 2013 VALID 101200Z - 111200Z ...THERE IS A SLGT RISK OF SVR TSTMS FOR UPSTATE NY SWWD ACROSS THE OH VALLEY TO THE OZARK PLATEAU... ...THERE IS A SLGT RISK OF SVR TSTMS FOR THE CNTRL HIGH PLAINS... ...SYNOPSIS... A SERIES OF UPPER-LEVEL SHORTWAVE TROUGHS WILL MOVE ACROSS THE GREAT LAKES REGION TODAY. THE FIRST WILL EXIT NEWD ACROSS ONTARIO INTO QUEBEC BY AFTERNOON...WHILE A SECOND DIGS SEWD OVERNIGHT. COLD FRONT ASSOCIATED WITH THE FIRST WAVE WILL EXTEND SWWD FROM LOWER MI INTO SRN KS THIS MORNING...WHERE IT WILL THEN TRANSITION TO A QUASI-STATIONARY FRONT THAT EXTENDS NWWD INTO ERN CO/WY. AS THE AFTERNOON PROGRESSES...THE COLD FRONT WILL ADVANCE SEWD AND EXTEND FROM THE OZARKS NEWD UP THE OH VALLEY. FARTHER W...UPPER-LEVEL RIDGING WILL OCCUR OVER THE ROCKIES AHEAD OF A TROUGH ENTERING THE PAC COAST. SURFACE HIGH PRESSURE WILL GRADUALLY MOVE E INTO THE UPPER MS VALLEY...WITH LOW-LEVEL SSELY RETURN FLOW DEVELOPING OVER THE CNTRL/NRN HIGH PLAINS. ...UPSTATE NY SWWD INTO THE OH VALLEY AND OZARK PLATEAU... A VERY MOIST AIRMASS...WITH DEWPOINTS IN THE UPPER 60S TO MID 70S...WILL RESIDE ALONG THE LENGTH OF A COLD FRONT THIS AFTERNOON. THIS MOISTURE COMBINED WITH DAYTIME HEATING WILL YIELD MLCAPE VALUES IN EXCESS OF 2000 J/KG. THE WARM/UNSTABLE BOUNDARY LAYER COMBINED WITH FRONTAL CONVERGENCE/ASCENT WILL AID IN SCATTERED THUNDERSTORM DEVELOPMENT...POSSIBLY AS EARLY AS LATE MORNING OVER THE MID OH VALLEY INTO WRN NY. STRONGEST MIDLEVEL WNWLYS...RANGING FROM 20-40 KT...WILL BE SITUATED FROM UPSTATE NY SWWD INTO OH...AND WILL SUPPORT ORGANIZED MULTICELL CLUSTERS/LINES AND PERHAPS A FEW SUPERCELLS POSING A THREAT FOR LARGE HAIL AND DAMAGING WIND GUSTS. VERTICAL WIND SHEAR WILL BE WEAKER FROM THE LOWER OH VALLEY WWD TO THE OZARK PLATEAU. HOWEVER...STRONG INSTABILITY...PW VALUES NEAR 2.0 INCHES...AND HOT SURFACE TEMPERATURES/STEEP LOW-LEVEL LAPSE RATES WILL LEAD TO A RISK FOR DAMAGING DOWNBURSTS AND ISOLATED LARGE HAIL. ...CNTRL HIGH PLAINS... SELY UPSLOPE FLOW WILL OCCUR ACROSS THE COOL SIDE OF A STATIONARY FRONT OVER THE HIGH PLAINS...AND AID IN TRANSPORTING MEAN BOUNDARY LAYER MIXING RATIOS FROM 9-12 G/KG INTO THE REGION. THIS MOISTURE COMBINED WITH BOUNDARY LAYER HEATING AND STEEP MIDLEVEL LAPSE RATES WILL LEAD TO MLCAPE VALUES FROM 1000-2000 J/KG. LOW-LEVEL SELYS VEERING TO WNWLY IN THE MID/UPPER-LEVELS...WHERE SPEEDS WILL RANGE FROM 20-40 KT...WILL YIELD EFFECTIVE BULK SHEAR VALUES UP TO 50 KT. THE COMBINATION OF AN UNSTABLE AND STRONGLY SHEARED ENVIRONMENT WILL FAVOR SUPERCELL DEVELOPMENT AND A RISK FOR LARGE HAIL. ...CNTRL/SRN KS...OK... ISOLATED/SCATTERED THUNDERSTORMS ARE FORECAST TO DEVELOP DURING THE AFTERNOON ACROSS CNTRL/SRN KS INTO OK. SURFACE TEMPERATURES NEAR 100F WILL YIELD LARGE BOUNDARY LAYER DEWPOINT DEPRESSIONS AND STEEP LOW-LEVEL LAPSE RATES...WHILE PW VALUES FROM 1.5-2.0 INCHES AIDS IN MLCAPE VALUES FROM 1000-2500 J/KG. THIS ENVIRONMENT WILL SUPPORT A THREAT FOR ISOLATED DAMAGING WINDS AND LARGE HAIL. ...SERN/S-CNTRL AZ...SWRN NM... A WARM BOUNDARY LAYER COMBINED WITH PW VALUES EXCEEDING 1.0 INCH WILL AID IN WEAK TO MODERATE INSTABILITY ACROSS SERN/S-CNTRL AZ INTO SWRN NM...AND WILL SUPPORT ISOLATED/SCATTERED THUNDERSTORM DEVELOPMENT DURING THE AFTERNOON AND EVENING. CONTINUED PRESENCE OF LOW-LEVEL WLY FLOW OCCURRING BENEATH 20-30 KT MIDLEVEL ELYS MAY AID IN MODEST STORM ORGANIZATION WITH AN ASSOCIATED RISK FOR ISOLATED DAMAGING WINDS AND LARGE HAIL. ..GARNER/SMITH.. 07/10/2013
via SPC Forecast Products http://www.spc.noaa.gov/products/outlook/day1otlk_1200.html
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