The SPC is forecasting ...significant severe thunderstorms expected from east texas across the gulf coast states today and tonight.... Please read the latest public statement about this event. View What is a Watch? clip.
| Categorical Graphic |
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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. |
| 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. |
| 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. |
SPC AC 251228 DAY 1 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 0628 AM CST TUE DEC 25 2012 VALID 251300Z - 261200Z ...THERE IS A MDT RISK OF SVR TSTMS FROM SERN TX THROUGH PORTIONS OF CNTRL/SRN LA...CNTRL/SRN MS INTO THE SWRN QUARTER OF AL AND THE WRN FL PNHDL... ...THERE IS A SLGT RISK OF SVR TSTMS FROM CNTRL TX EWD ACROSS THE GULF COAST STATES TO WRN SC... --SEVERE WEATHER OUTBREAK LIKELY TODAY AND TONIGHT FROM SERN TX ACROSS THE GULF COAST STATES. STRONG...LONG-TRACKED TORNADOES AND WIDESPREAD DAMAGING WINDS POSSIBLE-- ...SYNOPSIS... A 100+KT MIDLEVEL JET STREAK OVER SWRN TX WILL PROGRESS ESEWD TO ALONG THE CNTRL GULF COAST BY LATE TONIGHT/EARLY WEDNESDAY... CONTRIBUTING TO SUBSEQUENT AMPLIFICATION OF THE COMPANION SHORTWAVE TROUGH AND EVENTUAL EVOLUTION OF A CLOSED CIRCULATION OVER THE LOWER MS VALLEY. THESE DEVELOPMENTS WILL PROMOTE SIGNIFICANT FORCING FOR ASCENT WITH A CORRIDOR OF 500-MB HEIGHT FALLS OF 100-150M/12HR SPREADING FROM CNTRL TX INTO THE TN VALLEY BY 26/12Z. IN THE LOW LEVELS...SURFACE CYCLONE OVER THE TX HILL COUNTRY WILL DEEPEN TODAY WHILE DEVELOPING ENEWD ALONG A RETREATING WARM FRONT INTO W-CNTRL MS BY 26/00Z AND MIDDLE TN BY THE END OF THE D1 PERIOD. MEANWHILE...A STRENGTHENING COLD FRONT WILL SWEEP EWD THROUGH THE SABINE RIVER VALLEY TODAY AND THE LOWER MS VALLEY OVERNIGHT. ...ERN TX EWD ACROSS THE GULF COAST STATES... A NW-SE ORIENTED BAND OF ELEVATED TSTMS IS IN PROGRESS THIS MORNING TO THE NORTH OF THE SURFACE WARM FRONT FROM N-CNTRL/NERN TX INTO CNTRL LA...DRIVEN BY ISENTROPIC ASCENT AND WAA AT THE TERMINUS OF AN INTENSIFYING LLJ. HERE...STEEPENING MIDLEVEL LAPSE RATES COINCIDE WITH A MOISTENING...LOW-LEVEL AIR MASS...CONTRIBUTING TO MUCAPE VALUES OF 1000-1500 J/KG PER 12Z FWD SOUNDING. GIVEN A KINEMATIC ENVIRONMENT FEATURING 35-50 KT OF EFFECTIVE BULK SHEAR...THE SETUP WILL REMAIN SUPPORTIVE OF SUPERCELLS CAPABLE OF LARGE HAIL. TO THE S/SW OF THE ELEVATED TSTMS...AN OVERALL DEEPENING TO THE SYNOPTIC SYSTEM WILL RESULT IN THE INTENSIFICATION AND BROADENING OF A LLJ WHICH WILL AID IN THE NWD EXPANSION OF THE WARM SECTOR FROM THE GULF COAST TODAY. WHILE DAYTIME HEATING WILL BE LIMITED BY WIDESPREAD CLOUDS...STEEPENING MIDLEVEL LAPSE RATES AND BOUNDARY LAYER DEWPOINTS RISING INTO THE MID 60S WILL YIELD A MODERATELY UNSTABLE AIR MASS BY AFTERNOON TO THE S OF THE WARM FRONT WHERE MLCAPE VALUES WILL APPROACH 1000-1500 J/KG. LATEST CONVECTION-ALLOWING MODEL GUIDANCE SUGGESTS THAT SURFACE-BASED OR NEAR SURFACE BASED STORMS /INCLUDING SUPERCELLS/ WILL DEVELOP AND INCREASE IN COVERAGE THIS MORNING INTO AFTERNOON INVOF THE RETREATING WARM FRONT OVER PORTIONS OF SERN TX EWD INTO CNTRL LA. BY MID TO LATE AFTERNOON...THESE DATA SUGGEST THAT STORMS WILL BECOME ORIENTED IN A N-S ORIENTED BROKEN BAND /LIKELY COMPRISED OF SUPERCELLS AND BOWING SEGMENTS/ FROM NEAR THE DEEPENING SURFACE LOW ALONG THE MS/LA BORDER SWD ALONG THE SURGING COLD FRONT. A SIMILAR CONVECTIVE CONFIGURATION IS LIKELY TO PERSIST ACROSS MS AND AT LEAST THE WRN HALF OF AL THIS EVENING INTO TONIGHT. THEREAFTER...INTENSE DCVA ASSOCIATED WITH NEGATIVELY-TILTED UPPER SYSTEM AND LOW-LEVEL UPLIFT ALONG COLD FRONT MAY RESULT IN A TRANSITION TO A NARROW BUT CONTINUOUS CONVECTIVE BAND WHICH WILL ADVANCE EWD INTO GA...THE FL PNHDL AND WRN SC BY WEDNESDAY MORNING. THE EWD PROGRESSION OF THE 100+KT MIDLEVEL JET STREAK ACROSS THE WARM SECTOR AND CONCOMITANT INTENSIFICATION OF THE LLJ WILL RESULT IN STRENGTHENING LOW-LEVEL AND DEEP-LAYER SHEAR...ESPECIALLY DURING THE DEEPENING PHASE OF THE PARENT SYSTEM LATER TODAY INTO TONIGHT. INDEED...FORECAST HODOGRAPHS AND PLAN VIEW KINEMATIC FIELDS INDICATE EFFECTIVE BULK SHEAR VALUES OF 50-70 KT WITH EFFECTIVE SRH VALUES INCREASING FROM 200-350 M2/S2 TODAY...TO IN EXCESS OF 400-500 M2/S2 TONIGHT. EXPECT A MIXTURE OF SUPERCELLS AND BOWING LINE SEGMENTS/LEWPS TO EVOLVE WITH AN ASSOCIATED RISK FOR TORNADOES...SOME OF WHICH COULD BE POTENTIALLY LONG-TRACKED AND STRONG. DAMAGING WINDS WILL BECOME INCREASINGLY WIDESPREAD LATER THIS AFTERNOON INTO THE OVERNIGHT HOURS AS CONVECTION GROWS UPSCALE INTO A QLCS. FINALLY...HAIL --SOME IN EXCESS OF 2 INCHES IN DIAMETER-- WILL BE POSSIBLE... ESPECIALLY ACROSS PORTIONS OF SERN TX AND SWRN LA WHERE 12Z CRP/LCH SOUNDINGS SHOWED THE PRESENCE OF A WELL-DEFINED EML WITH 700-500-MB LAPSE RATES OF 8-8.5 C/KM. ..MEAD/LEITMAN.. 12/25/2012 CLICK TO GET WUUS01 PTSDY1 PRODUCT NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1630Z