The SPC is forecasting ...severe thunderstorms expected over parts of the southern plains and the arklatex region later today and tonight.... Please read the latest public statement about this event. View What is a Watch? clip.
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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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| 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 211628 DAY 1 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 1128 AM CDT TUE MAY 21 2013 VALID 211630Z - 221200Z ...THERE IS A MDT RISK OF SVR TSTMS FOR N-CNTRL/NERN TX...SRN AR...NWRN LA...FAR SERN OK... ...THERE IS A SLGT RISK OF SVR TSTMS FROM THE SRN PLAINS TO THE TN/OH VALLEYS AND THE LOWER GREAT LAKES/NORTHEAST... ...SUBSTANTIAL SEVERE WEATHER EXPECTED ACROSS N-CNTRL TX TO THE ARKLATEX THIS AFTERNOON AND EVENING... ..SRN PLAINS TO LOWER MS VALLEY... SIGNIFICANT SEVERE WEATHER EPISODE INITIALLY UNFOLDING ACROSS THE RED RIVER WITH SUPERCELLS PRODUCING LARGE HAIL ALONG AND N OF THE COMPOSITE OUTFLOW/COLD FRONT PUSHING SWD FROM THE BIG COUNTRY TO FAR SERN OK AHEAD OF A WELL-DEFINED SHORTWAVE TROUGH OVER THE SRN HIGH PLAINS. AIR MASS S OF THE BOUNDARY IS BECOMING STRONGLY UNSTABLE AS GRADUAL SURFACE HEATING CONTINUES AMIDST LOWEST 100 MB MEAN MIXING RATIOS OF 14-17 G/KG AND 700-500 MB LAPSE RATES OF 8 TO 9.5 DEG C/KM SAMPLED IN ALL REGIONAL 12Z RAOBS. AS MLCIN IS MINIMIZED ALONG THE DRYLINE MIXING EWD ACROSS THE EDWARDS PLATEAU...ADDITIONAL SUPERCELL DEVELOPMENT IS ANTICIPATED WITH SWD EXTENT. A BELT OF 50-60 KT MID-LEVEL SWLYS ATTENDANT TO THE COMPACT SHORTWAVE TROUGH WILL PROMOTE RISKS FOR ALL SEVERE TYPES /SOME OF WHICH WILL BE SIGNIFICANT/. MORNING CONVECTION-ALLOWING WRF AND HRRR SIMULATIONS ARE INSISTENT THAT UPSCALE GROWTH WILL OCCUR THROUGHOUT THE AFTERNOON. GIVEN THE DEGREE OF INSTABILITY...BUOYANCY AND SHEAR...SETUP MAY YIELD A DERECHO ACCELERATING EWD TOWARDS THE ARKLATEX REGION BY EARLY EVENING. HERE TOO...THE STRONGEST LOW-LEVEL S/SWLYS WILL REMAIN...PROMOTING EMBEDDED MESOVORTICES CAPABLE OF PRODUCING A COUPLE OF SIGNIFICANT TORNADOES. OTHERWISE...POTENTIAL DOES EXIST FOR WIDESPREAD/DESTRUCTIVE DAMAGING WIND GUSTS. ...TN VALLEY TO THE LOWER GREAT LAKES/NORTHEAST... A BROAD AREA OF ORGANIZED SEVERE POTENTIAL IS EXPECTED ALONG THE ERN EXTENT OF THE ELEVATED MIXED LAYER PLUME SAMPLED IN 12Z RAOBS. WITH ROBUST HEATING...MODERATE TO STRONG INSTABILITY IS ANTICIPATED...BUT MOST OF THE REGION WILL REMAIN ON THE FRINGE OF SUFFICIENT DEEP-LAYER SHEAR FOR SUPERCELLS. THREE ZONES OF FOCUS FOR SUSTAINED CONVECTION ARE APPARENT. ONE WILL BE DOWNSTREAM OF AN ONGOING CLUSTER ACROSS WRN TN. THE OTHERS SHOULD BE ALONG A QUASI-STATIONARY FRONT BISECTING NY INTO SRN NEW ENGLAND AND PERHAPS IN ASSOCIATION WITH A WEAK MCV MOVING INTO LOWER MI. MULTICELL CLUSTERS AND A FEW SUPERCELLS WILL BE PRIMARILY CAPABLE OF ISOLATED DAMAGING WINDS AND SEVERE HAIL. ..GRAMS/ROGERS.. 05/21/2013 CLICK TO GET WUUS01 PTSDY1 PRODUCT NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 2000Z |