The SPC is forecasting ...severe thunderstorms expected over parts of the lower mississippi valley later today and tonight.... Please read the latest public statement about this event.
| 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 251236 DAY 1 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 0736 AM CDT MON APR 25 2011 VALID 251300Z - 261200Z ...THERE IS A MDT RISK OF SVR TSTMS THIS AFTERNOON INTO TONIGHT FROM NE TX/SE OK ACROSS CENTRAL/SRN AR...NW LA...NW MS...AND FAR WRN TN... ...THERE IS A SLGT RISK OF SVR TSTMS SURROUNDING THE MDT RISK AREA...FROM ERN TX/OK NEWD TO THE LOWER OH VALLEY... ...THERE IS A SLGT RISK OF SVR TSTMS THIS AFTERNOON/EVENING FOR ERN OH AND PA... ...SYNOPSIS... A PRONOUNCED MIDLEVEL SHORTWAVE AND ASSOCIATED 70-80 KT MIDLEVEL JET OVER NM THIS MORNING WILL PROGRESS EWD OVER N TX/OK TODAY...AND NEWD OVER AR/MO TONIGHT. AN ASSOCIATED SURFACE CYCLONE IS EXPECTED TO DEVELOP NEWD FROM S CENTRAL OK THIS MORNING TO SW MO THIS EVENING AND NW IL LATE TONIGHT. A GRADUAL INCREASE IN THE WARM SECTOR SLY/SSWLY LLJ IS EXPECTED LATER TODAY INTO TONIGHT AS THE MIDLEVEL TROUGH EJECTS ENEWD AND THE SURFACE CYCLONE DEEPENS. INCREASING VERTICAL SHEAR IN A MOIST/UNSTABLE WARM SECTOR WILL SUPPORT A RISK FOR SIGNIFICANT SEVERE STORMS TODAY INTO TONIGHT...THOUGH SEVERAL MESOSCALE FACTORS ADD UNCERTAINTY TO THE FORECAST. ...NE TX/SE OK ENEWD TO WRN TN/NW MS THROUGH TONIGHT... COMPLICATED SCENARIO IS ALREADY UNFOLDING THIS MORNING WITH THE WEAKENING COLD POOL FROM OVERNIGHT CONVECTION BEING OVERTAKEN BY ANOTHER MCS MOVING ALONG THE OUTFLOW BOUNDARY INTO SW AR. THIS MCS WILL LIKELY PERSIST THROUGH MUCH OF THE DAY WHILE PROGRESSING ACROSS MUCH OF CENTRAL/SRN AR...GENERATING ANOTHER COLD POOL AND INHIBITING NWD PROGRESS OF THE WARM SECTOR IN AR. THE MCS WILL INITIALLY POSE A THREAT FOR DAMAGING WINDS AND LARGE HAIL...THOUGH THERE IS SOME RISK FOR SUPERCELLS TO EVOLVE ON THE S/SW FLANK OF THE MCS AS THE BOUNDARY LAYER DESTABILIZES FROM NE TX INTO SRN AR. FARTHER W IN N/NE TX AND SE OK...SOME NWD RECOVERY IS EXPECTED IN THE WAKE OF THE MORNING STORMS...AND IN ADVANCE OF THE SURFACE CYCLONE. STRONG INSTABILITY /MLCAPE OF 2500-3500 J PER KG/ IS EXPECTED E/SE OF THE COLD FRONT/DRYLINE TRIPLE POINT IN N TX...AS A RESULT OF UPPER 60S BOUNDARY LAYER DEWPOINTS BENEATH 7-8 C/KM MIDLEVEL LAPSE RATES. ADDITIONAL SEVERE THUNDERSTORM DEVELOPMENT IS LIKELY BY EARLY-MID AFTERNOON NEAR THE TRIPLE POINT...WHERE THE STRONG INSTABILITY AND EFFECTIVE BULK SHEAR IN EXCESS OF 50 KT WILL FAVOR SUPERCELLS WITH VERY LARGE HAIL. THE BOUNDARY LAYER WILL BE SUFFICIENTLY MOIST AND LOW-LEVEL SHEAR WILL BE SUFFICIENTLY STRONG /EFFECTIVE SRH OF 250-350 M2 PER S2/ TO SUPPORT THE RISK FOR A FEW STRONG TORNADOES BEGINNING THIS AFTERNOON IN NE TX/SE OK...AND SPREADING INTO NW LA AND CENTRAL/SRN AR LATER THIS EVENING AND CONTINUING INTO TONIGHT. ...NRN AR/SRN MO/IL THROUGH TONIGHT... THE NRN EXTENT OF THE MORE SIGNIFICANT SEVERE THUNDERSTORM/TORNADO THREAT IS QUITE UNCERTAIN GIVEN THE STABILIZING IMPACTS OF ONGOING AND EXPECTED THUNDERSTORM CLUSTERS. AT THIS TIME...IT APPEARS THAT THE NWD EXTENT OF THE STRONGER INSTABILITY WILL BE LIMITED BY MULTIPLE THUNDERSTORM CLUSTERS AND CONVECTIVE OUTFLOWS...SUCH THAT ONLY WEAK INSTABILITY IS LIKELY INVOF THE DEEPENING SURFACE CYCLONE THIS EVENING INTO TONIGHT. DEEP-LAYER AND LOW-LEVEL VERTICAL SHEAR WILL BE SUFFICIENT FOR ORGANIZED SEVERE STORMS...BUT THE WEAK INSTABILITY AND WIDESPREAD CONVECTION FARTHER TO THE S WILL TEND TO LIMIT THE OVERALL DAMAGING WIND AND TORNADO RISK THIS FAR N. ...ERN OH/PA THIS AFTERNOON/EVENING... A LOW-AMPLITUDE SHORTWAVE TROUGH OVER THE LOWER OH RIVER THIS MORNING WILL EJECT ENEWD TOWARD NE OH/NW PA BY THIS EVENING...AND THIS WAVE WILL BE PRECEDED BY A WEAK SURFACE LOW ALONG A SLOW-MOVING WARM FRONT THAT WILL DRIFT NWD ACROSS PA TODAY. THE FOCUS FOR THUNDERSTORM DEVELOPMENT WILL BE BETTER DEFINED ACROSS ERN OH/NW PA THIS AFTERNOON ALONG THE PATH OF THE WEAK WAVE...BUT THERE ARE SOME CONCERNS REGARDING THE MAGNITUDE OF THE INSTABILITY BASED ON LINGERING CLOUDS/RAIN. FARTHER E IN PA...SOMEWHAT RICHER LOW-LEVEL MOISTURE AND STRONGER SURFACE HEATING ARE EXPECTED E OF THE MOUNTAINS. HERE...THERE WILL BE NO CLEAR FOCUS FOR STORM DEVELOPMENT ASIDE FROM THE WARM FRONT. IF STORMS DO FORM...VERTICAL SHEAR AND INSTABILITY COULD SUPPORT SUPERCELLS WITH DAMAGING WINDS AND SOME HAIL. ...TX PANHANDLE THIS AFTERNOON... THERE WILL BE A NARROW WINDOW OF OPPORTUNITY FOR SURFACE-BASED THUNDERSTORM DEVELOPMENT THIS AFTERNOON IN A NW-SE CORRIDOR ALONG THE COLD FRONT...WITH THE MIDLEVEL TROUGH OVERHEAD. SURFACE HEATING AND 500 MB TEMPERATURES NEAR -20 C COULD SUPPORT HIGH-BASED/LOW-TOPPED STORMS ALONG THE FRONT. GIVEN COLD TEMPERATURES ALOFT AND INVERTED-V PROFILES IN THE LOW LEVELS...HAIL AND STRONG OUTFLOW WINDS WILL BE POSSIBLE WITH MARGINAL SUPERCELL-TYPE STORMS. ..THOMPSON/COHEN.. 04/25/2011 CLICK TO GET WUUS01 PTSDY1 PRODUCT NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1630Z