SPC 1300Z Day 1 Outlook
DAY 1 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 0644 AM CST SAT JAN 12 2013 VALID 121300Z - 131200Z ...THERE IS A SLGT RISK OF SVR TSTMS THIS AFTERNOON INTO TONIGHT FROM NE TX ACROSS AR TO EXTREME WRN TN/KY... ...NE TX TO WRN TN/KY THROUGH TONIGHT... AN EMBEDDED SHORTWAVE TROUGH OVER AZ/NM/NW MEXICO THIS MORNING WILL EJECT NEWD OVER TX/OK/KS BY LATE EVENING AND REACH MO/IA OVERNIGHT. AN ASSOCIATED WEAK SURFACE WAVE WILL FORM ALONG A SLOW-MOVING FRONT AND MOVE FROM NE TX THIS AFTERNOON TO THE OH VALLEY OVERNIGHT. MEANWHILE...RICH LOW-LEVEL MOISTURE /BOUNDARY LAYER DEWPOINTS OF 65-70 F/ IS OVERSPREADING THE AREA FROM E TX TO LOWER MS VALLEY...TO THE SOUTH OF THE COLD FRONT. A FEW ELEVATED THUNDERSTORMS ARE ONGOING FROM NRN LA TO NRN MS ALONG THE LOW-LEVEL MOISTURE GRADIENT...WITHIN A ZONE OF LOW-LEVEL WAA. CONVECTION WILL LIKELY PERSIST THROUGH THE DAY ALONG THIS CORRIDOR...WHICH WILL SHIFT SLOWLY NWD TO NE TX/AR/WRN TX DURING THE DAY. ALONG AND S OF THE BAND OF ELEVATED CONVECTION...GRADUALLY INCREASING MOISTURE AND SOME SURFACE HEATING IN CLOUD BREAKS WILL CONTRIBUTE TO MLCAPE OF 500-1000 J/KG BY LATER THIS AFTERNOON. MEANWHILE...VERTICAL SHEAR WILL BE FAVORABLE FOR SUPERCELLS GIVEN SWLY MIDLEVEL FLOW OF 60-70 KT ABOVE A 50 KT SSWLY LLJ...RESULTING IN LONG HODOGRAPHS WITH SUBSTANTIAL DEEP-LAYER AND LOW-LEVEL VERTICAL SHEAR. THE MOST PROBABLE SCENARIO APPEARS TO BE FOR A ELEVATED STORMS TO SLOWLY EXPAND IN COVERAGE THROUGH THE DAY...WITH AN INCREASING CHANCE FOR SURFACE-BASED STORMS BY THIS AFTERNOON/EVENING ALONG THE SRN FRINGE OF THE CONVECTION WHICH WILL TEND TO CONSOLIDATE WITHIN THE FRONTAL ZONE AND JUST AHEAD OF THE SURFACE WAVE. RATHER MODEST LAPSE RATES SUGGEST THAT HAIL WILL NOT BE MUCH OF A CONCERN...BUT HIGH-MOMENTUM FLOW JUST ABOVE THE GROUND AND EFFECTIVE SRH OF 250-350 M2/S2 WILL SUPPORT A RISK FOR DAMAGING GUSTS AND A COUPLE OF TORNADOES WITH EMBEDDED SUPERCELLS LATER THIS AFTERNOON INTO TONIGHT. THE SEVERE THREAT SHOULD DECREASE LATE TONIGHT AS INSTABILITY WEAKENS AND THE MAJORITY OF THE CONVECTION BECOMES ROOTED JUST ABOVE THE SURFACE COLD FRONT TRAILING THE SURFACE WAVE. ..THOMPSON/DISPIGNA.. 01/12/2013
via SPC Forecast Products http://www.spc.noaa.gov/products/outlook/day1otlk_1300.html
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