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| Probabilistic Tornado Graphic | |||||||||
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| Probability of a tornado within 25 miles of a point. Hatched Area: 10% or greater probability of EF2 - EF5 tornadoes within 25 miles of a point. |
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| Probabilistic Damaging Wind Graphic | |||||||||
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| Probability of damaging thunderstorm winds or wind gusts of 50 knots or higher within 25 miles of a point. Hatched Area: 10% of greater probability of wind gusts 65 knots or greater within 25 miles of a point. |
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| Probabilistic Large Hail Graphic | |||||||||
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| Probability of hail 1" or larger within 25 miles of a point. Hatched Area: 10% or greater probability of hail 2" or larger within 25 miles of a point. |
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SPC AC 271254 DAY 1 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 0754 AM CDT SAT APR 27 2013 VALID 271300Z - 281200Z ...THERE IS A SLGT RISK OF SVR TSTMS THIS AFTERNOON INTO EARLY TONIGHT FROM SW TX TO NW MS/SW TN... ...SYNOPSIS... A WEAK MIDLEVEL LOW OVER SE KS...AND A TRAILING SHORTWAVE TROUGH OVER CENTRAL/ERN OK...WILL MOVE EWD TO THE TN AND LOWER OH VALLEY REGIONS BY EARLY SUNDAY. AT THE SURFACE...A WEAK LOW IN SE OK WILL TRANSLATE NEWD TO THE LOWER OH VALLEY ALONG A PRE-EXISTING BAROCLINIC ZONE...IN ADVANCE OF THE MIDLEVEL TROUGH. A SWATH OF MID-UPPER 60S BOUNDARY LAYER DEWPOINTS HAS SPREAD INLAND ACROSS LA AND SRN/ERN TX. THIS MOIST SECTOR WILL EXPAND TODAY ACROSS SE AR/NRN MS/NW AL AND WRN/MIDDLE TN...IMMEDIATELY S OF THE FRONT THAT WILL BE REINFORCED BY CONVECTION THIS MORNING. ...SE AR/NW MS/SW TN THIS AFTERNOON INTO EARLY TONIGHT... MLCAPE VALUES ARE EXPECTED TO REACH THE 1500-2500 J/KG RANGE BY AFTERNOON WITH SURFACE HEATING ON THE SRN FRINGE OF THE MORNING CLOUDS/CONVECTION...AS LOW-LEVEL MOISTURE INCREASES FROM THE S/SW. MEANWHILE...DEEP-LAYER VERTICAL SHEAR WILL BE FAVORABLE FOR ORGANIZED CLUSTERS/LINE SEGMENTS...AS WELL AS SUPERCELLS...AS THE SHORTWAVE TROUGH PIVOTS EWD FROM OK TO AR. THE PRIMARY SEVERE RISKS WILL BE DAMAGING GUSTS AND LARGE HAIL WITH A BAND OF STORMS NEAR THE SURFACE LOW AND ALONG THE TRAILING COLD FRONT THIS AFTERNOON THROUGH EARLY TONIGHT. THOUGH LOW-LEVEL SHEAR WILL NOT BE PARTICULARLY STRONG...SOME ENHANCEMENT TO HODOGRAPH CURVATURE AND RESULTANT EFFECTIVE SRH NEAR 200 M2/S2 COULD SUPPORT AN ISOLATED TORNADO THIS AFTERNOON/EVENING FROM ERN AR INTO NW MS/SW TN. ...TX BIG BEND/RIO GRANDE VALLEY THIS AFTERNOON INTO TONIGHT... BOUNDARY LAYER DEWPOINTS IN THE 68-70 F RANGE HAVE OVERSPREAD S AND SE TX THIS MORNING...BENEATH A RESIDUAL STEEP MIDLEVEL LAPSE RATE PLUME. THOUGH THE PRIMARY SYNOPTIC WAVE WILL PROGRESS AWAY FROM THIS AREA THROUGH TONIGHT...A BAND OF 30-40 KT WSWLY MIDLEVEL FLOW WILL PERSIST INVOF THE SLOW-MOVING FRONT ACROSS SW AND CENTRAL TX. THUS...THE COMBINATION OF BUOYANCY AND VERTICAL SHEAR WILL BE FAVORABLE FOR ORGANIZED CLUSTERS AND SUPERCELLS AS STORMS FORM LATE THIS AFTERNOON ALONG THE FRONT FROM SW INTO CENTRAL TX...AS WELL AS OVER THE HIGH TERRAIN IN NE MEXICO. LARGE HAIL WILL BE THE PRIMARY RISK INITIALLY WITH SPLITTING STORMS. OUTFLOW MERGERS AND UPSCALE GROWTH SHOULD SUPPORT SOME INCREASE IN THE DAMAGING WIND RISK THIS EVENING INTO EARLY TONIGHT...AS STORMS PROPAGATE SEWD INTO S TX BEFORE WEAKENING. ...E TX AREA THIS AFTERNOON... THOUGH LARGE SCALE FORCING FOR ASCENT MAY REMAIN RATHER WEAK THROUGH THIS AFTERNOON...SUBSTANTIAL SURFACE HEATING AND LOW-LEVEL CONVERGENCE ALONG A SURFACE COLD FRONT MAY PROMOTE THUNDERSTORM DEVELOPMENT. MLCAPE WILL POTENTIALLY REACH 2500 J/KG WITH STEEP MIDLEVEL LAPSE RATES...THOUGH LOW-LEVEL FLOW/SHEAR WILL REMAIN WEAK. THE NET RESULT WILL BE AN ENVIRONMENT SUPPORTIVE OF LARGE HAIL...AND THERE WILL BE ENOUGH OF A RISK FOR THUNDERSTORM INITIATION TO WARRANT EXPANSION OF THE CATEGORICAL SLIGHT RISK INTO THIS AREA FOR THIS AFTERNOON. ..THOMPSON/COHEN.. 04/27/2013 CLICK TO GET WUUS01 PTSDY1 PRODUCT NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1630Z |