The SPC is forecasting ...severe thunderstorms expected over parts of the cntrl plains...srn plains and ozarks this afternoon and evening.... Please read the latest public statement about this event.
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SPC AC 091946 DAY 1 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 0246 PM CDT THU APR 09 2009 VALID 092000Z - 101200Z ...THERE IS A MDT RISK OF SVR TSTMS THIS AFTERNOON INTO TONIGHT OVER PARTS OF ERN OK/WRN AR INTO SERN KS AND SWRN MO... ...THERE IS A SLGT RISK OF SVR TSTMS FROM PORTIONS OF THE CNTRL/SRN PLAINS INTO THE LOWER OH AND PARTS OF THE LOWER MS VALLEY... ...SRN/CNTRL PLAINS EWD INTO THE LOWER OH VALLEY AND CNTRL/ERN GULF STATES... LITTLE CHANGE TO KS/OK PORTION OF OUTLOOK WITH NEAR TERM DETAILS PROVIDED BY MCD/S 411 AND 412 AND WW 123. OVER TX...DRYLINE IS NEARING THE I-35 CORRIDOR AS OF 19Z AND SIGNIFICANT DIABATIC HEATING HAS OCCURRED W OF THIS BOUNDARY WITH TEMPERATURES NOW AROUND 90 F. PER 18Z FWD SOUNDING...THESE TEMPERATURES APPEAR TO BE SUFFICIENT TO ERODE THE CAP BASED AROUND 900 MB. LATEST MODEL GUIDANCE SUGGESTS THAT THE SRN FRINGE OF STRONGER HEIGHT FALLS ATTENDANT TO UPPER SYSTEM WILL REMAIN GENERALLY N OF I-20...LEAVING SOME UNCERTAINTY HOW FAR S DIURNAL STORM DEVELOPMENT WILL OCCUR. SHOULD TSTMS INITIATE AND BECOME SUSTAINED...THE PRESENCE OF THE STEEP LAPSE RATES AND 40-45 KT OF DEEP-LAYER SHEAR INDICATE THE POTENTIAL FOR ORGANIZED/ROTATING STORMS CAPABLE OF MAINLY LARGE HAIL AND DAMAGING WINDS. REF MCD 413 FOR ADDITIONAL NEAR TERM DETAILS IN THIS REGION. ELSEWHERE...HIGHER TORNADO PROBABILITIES WERE EXTENDED EWD THROUGH NERN AR/SERN MO INTO WRN PARTS OF KY/TN. WHILE UPSCALE GROWTH INTO AN MCS IS STILL ANTICIPATED...THE COMBINATION OF THE STEEP LAPSE RATES...INCREASING BOUNDARY LAYER MOISTURE AND STRONG LOW-LEVEL SHEAR ALL SUGGEST THE POTENTIAL FOR EMBEDDED TORNADIC SUPERCELLS OVERNIGHT...PARTICULARLY ON THE SRN FRINGE OF ANY LARGER-SCALE TSTM CLUSTER. OVER PORTIONS OF MIDDLE/ERN TN INTO NRN AL/NWRN GA...THE THREAT FOR ISOLATED SEVERE WEATHER IS EXPECTED TO INCREASE LATE TONIGHT INTO FRIDAY MORNING ALONG ERN EXTENSION OF LLJ AXIS. HERE...LOW-LEVEL MOISTENING WILL BE OCCURRING BENEATH STEEPENING MIDLEVEL LAPSE RATES...RESULTING IN RAPID AIR MASS DESTABILIZATION. AS SUCH...THE THREAT WILL EXIST FOR A FEW INTENSE STORMS /LIKELY SLIGHTLY ELEVATED/ WITH THE POTENTIAL FOR SOME HAIL. ..MEAD.. 04/09/2009 .PREV DISCUSSION... /ISSUED 1115 AM CDT THU APR 09 2009/ PREVIOUS FORECAST LOOKS ON TRACK FOR A FOCUSED BUT POTENTIALLY SIGNIFICANT SEVERE WEATHER EVENT LATER THIS AFTERNOON/EVENING IN ADVANCE OF THE STRONG UPPER TROUGH CURRENTLY MOVING EWD ACROSS SRN HIGH PLAINS. AN ELONGATED SURFACE LOW ALONG KS/OK BORDER WITH PRIMARY CENTER SWRN KS EXPECTED TO CONSOLIDATE AND MOVE EWD TO BE LOCATED S OF ICT BY LATER THIS AFTERNOON. ...SOUTHEASTERN KS/NORTHEASTERN OK THIS AFTERNOON... DRY LINE CURRENTLY SHARPENING UP WRN OK WILL BE PRIMARY FOCUS FOR SEVERE THUNDERSTORM INITIATION AFTER 21Z. RAPID MOISTENING OF THE BOUNDARY LAYER IS OCCURRING THIS MORNING AS STRONG SOUTHERLY LOW LEVEL JET TRANSPORTS GULF AIRMASS NORTHWARD INTO OK/AR. BY MID AFTERNOON...SURFACE DEWPOINTS IN THE MID TO UPPER 50S ARE EXPECTED OVER MOST OF EASTERN OK EAST OF THE DRYLINE...WITH NEAR 50F DEWPOINTS WRAPPING WESTWARD ALONG THE KS/OK BORDER NEAR THE SURFACE LOW. THE CAPPING INVERSION WILL SUPPRESS SURFACE-BASED CONVECTION OVER THIS REGION UNTIL EARLY THIS AFTERNOON. HOWEVER...IT APPEARS LIKELY THAT STRONG FORCING AND COOLING ALOFT WILL YIELD A NARROW ZONE OF WEAKENING CAP ALONG THE OK/KS BORDER BY 19-21Z. ISOLATED THUNDERSTORMS WILL LIKELY DEVELOP IN THIS ZONE AND TRACK NORTHEASTWARD INTO SOUTHEASTERN KS. FORECAST SOUNDINGS IN THIS REGION SUGGEST THE RISK OF RELATIVELY LOW-TOPPED SUPERCELLS CAPABLE OF HAIL AND ISOLATED TORNADOES. ...EASTERN OK/SOUTHWEST MO/WESTERN AR... ONLY ADJUSTMENT IN THIS AREA WAS TO SHIFT THE INITIATION ZONE A LITTLE FURTHER W BASED ON SUGGESTIONS BY HIGH RES MODELS AND RUC THAT THE STRONG HEATING COULD ERODE CAP SUFFICIENTLY ALONG DRY LINE TO REMOVE CINH PRIOR TO DRY LINE MIXING TO THE E OF A TUL/MLC LINE. UPON DEVELOPMENT...THESE STORMS WILL MOVE INTO SOUTHWEST MO AND WESTERN AR DURING THE EVENING. STEEP MID LEVEL LAPSE RATES AND COOL TEMPERATURES ALOFT...COUPLED WITH SUFFICIENT EFFECTIVE SHEAR FOR SUPERCELLS WILL PROMOTE THE RISK OF VERY LARGE HAIL IN STRONGER CELLS. FORECAST SOUNDINGS ALSO INDICATE SUBSTANTIAL VEERING AND INCREASING LOW LEVEL WINDS WITH HEIGHT...POSING A RISK OF SIGNIFICANT TORNADOES OVER THE MODERATE RISK AREA THROUGH EARLY EVENING. SURFACE DEWPOINT VALUES ARE ONLY FORECAST TO REACH THE LOWER 60S AT BEST ACROSS THE MDT AREA...BUT RAPIDLY COOLING TEMPERATURES ALOFT AND STRENGTH OF VERTICAL SHEAR EXPECTED TO RESULT IN MLCAPES TO 2000 J/KG AND WIND PROFILES MORE THAN SUFFICIENT TO SUPPORT DEVELOPMENT OF TORNADIC SUPERCELLS. OVERNIGHT...THUNDERSTORMS WILL LIKELY INCREASE IN COVERAGE AS THEY SPREAD EASTWARD ACROSS AR AND SOUTHERN MO INTO WESTERN KY/TN. THE SEVERE THREAT WILL LIKELY BECOME LESS ORGANIZED...BUT STRONGER CELLS WILL REMAIN CAPABLE OF HAIL AND DAMAGING WINDS MUCH OF THE NIGHT. CLICK TO GET WUUS01 PTSDY1 PRODUCT NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 0100Z