The SPC is forecasting ...an outbreak of severe thunderstorms including widespread damaging winds and a few strong tornadoes is expected over parts of the mid south across the lower ohio river valley and central gulf coast states today and tonight.... Please read the latest public statement about this event.
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SPC AC 050555 DAY 1 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 1155 PM CST MON FEB 04 2008 VALID 051200Z - 061200Z ...THERE IS A MDT RISK OF SVR TSTMS OVER MUCH OF AR...FAR NERN TX...NRN LA...CNTRL AND NRN MS...WRN TN...SERN MO...SRN IL AND FAR SWRN IND... ...THERE IS A SLGT RISK OF SVR TSTMS FROM THE SRN LOW PLAINS AND LOWER MS VALLEY NEWD INTO THE OH VALLEY... ...SYNOPSIS... STRONG...UPPER TROUGH CURRENTLY EVOLVING OVER THE FOUR CORNERS REGION WILL LIFT NEWD TODAY ACROSS THE SRN PLAINS INTO MID MS VALLEY AS MID AND UPPER-LEVEL JET STREAKS INTENSIFY IN THE DOWNSTREAM POSITION FROM THE ARKLATEX INTO LOWER OH VALLEY. IN THE LOW LEVELS...SURFACE LOW ALONG THE RED RIVER OVER S-CNTRL OK/N-CNTRL TX IS FORECAST TO DEEPEN SLIGHTLY WHILE DEVELOPING NEWD TO N-CNTRL AR BY 06/00Z AND INTO SRN OH BY THE END OF THE PERIOD. ATTENDANT DRY LINE INITIALLY FROM THE LOW SWD INTO CNTRL TX IS EXPECTED TO EVOLVE INTO A PACIFIC COLD FRONT WHILE PROGRESSING EWD THROUGH THE ARKLATEX. MEANWHILE...A STRONGER COLD FRONT WILL SURGE SEWD FROM CNTRL OK AND WRN TX...EVENTUALLY OVERTAKING PACIFIC COLD FRONT NEAR THE MS RIVER TONIGHT. ...SRN LOW PLAINS AND LOWER MS VALLEY NEWD INTO THE OH VALLEY... 05/00Z OBSERVED SOUNDINGS FROM THE TX COAST INTO LOWER MS VALLEY INDICATED THE PRESENCE OF A RELATIVELY STRONG CAP ATOP MODEST BOUNDARY LAYER MOISTURE WITH MEAN MIXING RATIOS OF 10-13 G/KG. A BROAD...SWLY LLJ ESTABLISHED FROM THE NWRN GULF OF MEXICO INTO THE LOWER GREAT LAKES WILL UNDERGO CONSIDERABLE STRENGTHENING TODAY...SUPPORTING A FURTHER INCREASE IN BOUNDARY LAYER MOISTURE CONTENT. SURFACE DEWPOINTS IN THE LOW TO MID 60S WILL BE COMMON ACROSS THE MID SOUTH WITH UPPER 60S TO AROUND 70 F ALONG THE GULF COAST. THIS MOISTURE COUPLED WITH MIDLEVEL LAPSE RATES OF 7-7.5 C/KM SHOULD SUPPORT A MODERATELY UNSTABLE AIR MASS /MLCAPES OF AROUND 1000 J PER KG/ BY AFTERNOON FROM SERN OK AND ERN TX EWD/NEWD ACROSS AR...LA AND MS. INSTABILITY WILL TEND TO DECREASE WITH NEWD EXTENT ACROSS THE OH VALLEY. TSTMS ARE EXPECTED TO BE ONGOING AT THE ONSET OF THE PERIOD ALONG FRONT FROM OH/IND/IL SWWD INTO SRN MO...WITH ONGOING OR DEVELOPING STORMS OVER PARTS OF CNTRL/ERN OK INTO N-CNTRL/CNTRL TX. LATEST SHORT TERM MODEL GUIDANCE SUGGESTS THAT THE MOST INTENSE STORMS WILL LIKELY OCCUR FROM VICINITY OF SURFACE LOW SWD ALONG PACIFIC COLD FRONT AS STRONG...DEEP LAYER FORCING FOR ASCENT OVERSPREADS DESTABILIZING WARM SECTOR. SOME UNCERTAINTIES IN THIS CONVECTIVE EVOLUTION REVOLVE AROUND: 1) WHETHER STORMS WILL REMAIN CONFINED TO ALONG THE FRONT AND 2) PRIMARY CONVECTIVE MODE. ETAKF SOUNDINGS WHICH APPEAR TO BETTER RESOLVE THE OBSERVED CAP TEND TO LIMIT STORMS TO ALONG THE FRONT. ONE POTENTIAL CAVEAT IS A RATHER WELL-DEFINED SHORT WAVE TROUGH EMBEDDED IN SUB-TROPICAL MOISTURE PLUME NEAR THE LOWER RIO GRANDE VALLEY AS OF 05/0530Z. THIS SYSTEM WILL PRECEED THE PRIMARY UPPER TROUGH...AND IT IS POSSIBLE THAT FORCING FOR ASCENT ASSOCIATED WITH THIS FEATURE COULD INITIATE MORE DISCRETE STORMS DOWNSTREAM FROM THE MAIN CONVECTIVE DEVELOPMENT ANTICIPATED ALONG THE FRONT. FORECAST SOUNDINGS INDICATE THAT THE MODERATE RISK AREA WARM SECTOR WILL BE STRONGLY SHEARED WITH EFFECTIVE SRH VALUES OF 250-350 M2/S2 AND EFFECTIVE BULK SHEARS OF 50-60 KT. ANY MORE DISCRETE STORMS THAT CAN DEVELOP WILL BE CAPABLE OF POTENTIALLY STRONG AND LONG-TRACK TORNADOES. LARGE HAIL WILL ALSO BE POSSIBLE...AS WILL CORRIDORS OF DAMAGING WINDS. THE WIND THREAT MAY TEND TO INCREASE TONIGHT OVER THE LOWER OH AND LOWER MS VALLEYS AND POINTS E AS STORMS GROW UPSCALE INTO A QUASI-LINEAR MCS. HIGH RESOLUTION MODEL DATA SETS SUGGEST THAT THE CHARACTER OF THIS MCS COULD BE SHORT...BROKEN LINES OF SUPERCELLS AND/OR BOWS WITH A CONTINUED THREAT OF STRONG TORNADOES. UNCERTAINTIES IN THE CONVECTIVE EVOLUTION GIVEN THE ABOVEMENTIONED...LEAD SHORT WAVE TROUGH AND PRIMARY CONVECTIVE MODE ARE GREAT ENOUGH SUCH THAT A CATEGORICAL MODERATE RISK WILL BE MAINTAINED. AN UPGRADE TO HIGH RISK MAY BECOME NECESSARY ONCE THESE DETAILS BECOME MORE CLEAR. ..MEAD.. 02/05/2008 CLICK TO GET WUUS01 PTSDY1 PRODUCT NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1300Z