The SPC is forecasting ...significant severe thunderstorms expected over parts of the southern plains high plains this afternoon into tonight.... Please read the latest public statement about this event.
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SPC AC 132232 DAY 1 CONVECTIVE OUTLOOK AMEND 1 NWS STORM PREDICTION CENTER NORMAN OK 0532 PM CDT SAT JUN 13 2009 VALID 132000Z - 141200Z ...THERE IS A MDT RISK OF SVR TSTMS ACROSS PARTS OF THE TX AND OK PANHANDLE REGION...AND INTO WRN OK/WRN N TX... ...THERE IS A SLGT RISK OF SVR TSTMS FROM THE CENTRAL AND SRN HIGH PLAINS SEWD INTO KS/OK/TX... ...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE SOUTHEAST AND THE LWR MS VALLEY... AMENDED FOR SLIGHT RISK ADDITION IN THE LWR MS VALLEY ...LWR MS VALLEY... PLEASE REFER TO SPC MESOSCALE DISCUSSION 1098 FOR DETAILS. ...SRN HIGH PLAINS... STORMS HAVE BEGUN DEVELOPING FROM THE TX SOUTH PLAINS REGION SWWD INTO THE TRANSPECOS REGION...AS DAYTIME HEATING HAS PUSHED TEMPERATURES INTO THE 90S/LOW 100S S OF THE SURFACE FRONT NOW LYING ACROSS NRN PORTIONS OF THE TX SOUTH PLAINS AND INTO THE RED RIVER VALLEY REGION. WITH DEWPOINTS GENERALLY IN THE 60S OVER THE HIGH PLAINS...MIXED-LAYER CAPE IN EXCESS OF 1500 J/KG HAS DEVELOPED THIS AFTERNOON. STORMS SHOULD CONTINUE TO DEVELOP ACROSS THIS REGION...AND EVENTUALLY NWD INTO THE TX PANHANDLE WHERE ELY UPSLOPE FLOW PERSISTS. STORMS WILL BECOME SUPERCELLULAR GIVEN FAVORABLE VEERING/SHEAR WITH HEIGHT IN PLACE ACROSS THIS REGION...WITH LARGE HAIL AND DAMAGING WINDS ANTICIPATED ALONG WITH AN ISOLATED TORNADO OR TWO. LATER...STORMS SHOULD DEVELOP/INCREASE NEAR AND N OF THE SURFACE FRONT ACROSS N TX/OK...WHERE VERY MOIST/STRONGLY-UNSTABLE AIRMASS IS EVIDENT. STORMS DEVELOPING/SPREADING EWD INTO OK/N TX MAY POSE A GREATER TORNADO POTENTIAL...GIVEN GREATER BOUNDARY-LAYER MOISTURE AND A MORE UNSTABLE AIRMASS. OVERNIGHT...STORMS SHOULD EVOLVE INTO A LARGE MCS...MOVING ACROSS OK AND VICINITY THROUGH THE END OF THE PERIOD -- ACCOMPANIED BY A CONTINUED THREAT FOR HAIL/DAMAGING WINDS. ...CENTRAL HIGH PLAINS... LOW-LEVEL MOISTURE CONTINUES ADVECTING NWWD INTO THE HIGH PLAINS...IN BROAD ZONE OF ELY/SELY FLOW W OF A SURFACE HIGH OVER THE MID MO VALLEY AND TO THE COOL SIDE OF THE SURFACE FRONT LYING FROM THE FRONT RANGE SWD INTO NERN NM. WITH 500 TO 1500 J/KG NOW INDICATED ALONG THE HIGH PLAINS...STORMS SHOULD CONTINUE TO INCREASE THROUGH THE AFTERNOON AND EVENING...EVENTUALLY SHIFTING INTO THE LOWER PLAINS OVERNIGHT AS THE LOW-LEVEL JET INCREASES. WITH MODERATE MID-LEVEL WLYS ATOP LOW-LEVEL VEERING...SHEAR WILL SUPPORT SUPERCELLS...WITH LARGE HAIL AND DAMAGING WINDS POSSIBLE IN ADDITION TO THE POTENTIAL FOR ISOLATED TORNADOES. OVERNIGHT...STORMS SHOULD CONTINUE SEWD -- MERGING INTO ONE OR MORE MCS WITH ASSOCIATED HAIL/WIND POTENTIAL THROUGH THE END OF THE PERIOD. ...SERN AL/SRN GA/NRN FL AND THE FL PANHANDLE... STORMS HAVE DEVELOPED IN A ROUGHLY W-E ARC ACROSS NRN FL...WHILE STORMS ONGOING EARLIER ACROSS AL HAVE MOVED SEWD INTO SERN AL/SWRN GA. WHILE DEEP-LAYER WIND FIELD REMAINS RELATIVELY WEAK...MODERATE INSTABILITY ACROSS THIS REGION SUGGESTS A CONTINUED THREAT FOR ISOLATED SEVERE STORMS THROUGH MID-EVENING. ..SELECT A FORECASTER.. 06/13/2009 .PREV DISCUSSION... /ISSUED 1126 AM CDT SAT JUN 13 2009/ ...SYNOPSIS... LITTLE OVERALL CHANGE IN LARGE SCALE PATTERN AS TROUGH PERSIST OVER WRN U.S...RIDGE ACROSS SRN PLAINS/LWR MS VALLEY AND TROUGH IN THE NORTHEAST. COMPOSITE OF A FRONTAL ZONE/CONVECTIVE OUTFLOW BOUNDARIES EXTENDS WWD FROM TN VALLEY THRU CENTRAL OK ACROSS TX PANHANDLE INTO ERN NM. A VERY MOIST AND POTENTIALLY EXTREMELY UNSTABLE AIR MASS RESIDES S OF SRN PLAINS PORTION OF SURFACE BOUNDARIES. ADDITIONALLY LOW LEVEL MOISTURE RETURNING NWD E OF FRONT RANGE CENTRAL HI PLAINS IN ADVANCE OF A SIGNIFICANT UPPER TROUGH CURRENTLY EJECTING FROM WRN TROUGH POSITION. ...WRN OK INTO NWRN TX AND THE TX PANHANDLE... WHILE THIS AREA WILL GENERALLY BY CAPPED THRU MID AFTERNOON UNDER THE RIDGE POSITION...VERY STRONG HEATING ALONG AND S OF FRONTAL ZONE WILL RAISE SFC TEMPS TO NEAR 100 F NWRN TX WHICH ALONG WITH DEWPOINTS NEAR OF ABOVE 70F BOTH VICINITY AND N OF BOUNDARY AND TO THE E OF WHERE DRY LINE IS ABLE TO MIX WILL PUT IN PLACE AN EXTREMELY UNSTABLE AIR MASS WITH MLCAPES AOA 4500 J/KG. GIVEN THE LACK OF AVAILABLE LARGE SCALE LIFT AS AREA IN THE RIDGE POSITION...SURFACE BASED STORMS EXPECTED TO FORM IN LOW LEVEL CONVERGENCE BOTH VICINITY E/W BOUNDARY AND THE INTERFACE OF THE STRONGLY HEATED/STEEP LAPSE RATE ENVIRONMENT VICINITY N/S DRY LINE WCENTRAL TX. MOST FAVORED REGION FOR SUPERCELLS AND LARGE HAIL/WIND DAMAGE WILL BE ALONG AND ON THE COOL SIDE OF E/W FRONTAL ZONE WHERE GREATEST LOW LEVEL SHEAR WILL RESIDE. ADDITIONALLY SEVERE STORMS EXPECTED TO DEVELOP IN UPSLOPE REGION NERN NM AS MOIST LOW LEVEL AIRMASS SPREADS WWD. SUPERCELLS WOULD THEN LIKELY DEVELOP EWD ACROSS TX/OK PANHANDLE BY THIS EVENING WITH POTENTIAL FOR VERY LARGE HAIL...AT LEAST ISOLATED TORNADOES AS THIS AREA WILL HAVE A FAVORABLE VEERING LOW LEVEL SHEAR ENVIRONMENT/LARGE HODOGRAPHS AND RELATIVELY LOW LFC/S. HAVE SHIFTED THE ORIGINAL MDT TO THE N AND W BASED ON THESE REASONINGS WITH MORE ISOLATED SEVERE STORMS EXPECTED WITH SWD EXTENT INTO SWRN TX AS CAP WILL BE STRONGER UNDER RIDGE ALONG WITH WEAKER SHEAR. SEVERE STORMS DEVELOPING EWD ACROSS MDT RISK AREA THIS EVENING WILL LIKELY FORM ONE OR MORE MCS/S IN RESPONSE TO FORECASTED INCREASE IN THE LOW LEVEL JET TO 30-40KT AND ASSOCIATED WARM ADVECTION. THIS WILL MAINTAIN A SEVERE THREAT INCLUDING DAMAGING WINDS/LARGE HAIL E/NEWD ACROSS OK/SRN KS TONIGHT. ...CENTRAL HIGH PLAINS... WITH LOW LEVEL MOISTURE RETURNING NWD IN ADVANCE OF UPPER TROUGH LIFTING NEWD ACROSS CENTRAL ROCKIES THIS AFTERNOON...EXPECT MORE THAN SUFFICIENT INSTABILITY AND SHEAR TO BE IN PLACE FOR SEVERE STORM DEVELOPMENT TODAY AS FAR N AS ERN WY. AS 50 DEWPOINTS/STEEP LAPSE RATES AND INCREASING SHEAR WITH MID LEVEL SWLY FLOW OF 40-50 KTS SPREADING ACROSS FRONT RANGE...SEVERE THUNDERSTORMS INCLUDING SUPERCELLS WILL DEVELOP ALONG AND E OF FRONT RANGE BASED ON THESE EXPECTED CONDITIONS NWD INTO SERN WY. FURTHER W INTO CENTRAL WY...THE AIR MASS WILL DESTABILIZE AND SUPPORT ACTIVE THUNDERSTORMS AHEAD OF UPPER TROUGH WHICH WILL INCLUDE BOTH HAIL AND DAMAGING WINDS BY MID AFTERNOON. LOW LEVEL SHEAR/MOISTURE WILL BE A LITTLE LESS FAVORABLE THAN FURTHER E...BUT GIVEN THE LARGE SCALE ASCENT WITH TROUGH AT LEAST ISOLATED SUPERCELLS ARE LIKELY. ...MS/AL/GA/FL... SCATTERED THUNDERSTORMS ARE ONGOING THIS MORNING OVER PARTS OF MS/AL. THIS ACTIVITY MAY INTENSIFY EARLY THIS AFTERNOON AS DAYTIME HEATING DESTABILIZES THE AIRMASS. ISOLATED SEVERE STORMS CAPABLE OF HAIL AND DAMAGING WINDS ARE EXPECTED THROUGH THE DAY AS STORMS SPREAD EAST-SOUTHEASTWARD TOWARD GA/FL PANHANDLE. ...UPPER MS VALLEY... STEEP LOW LEVEL LAPSE RATES...COOL TEMPERATURE PROFILES AND MARGINAL INSTABILITY EXPECTED TO BE SUFFICIENT FOR A FEW STRONG/SEVERE THUNDERSTORMS ALONG/AHEAD OF FRONT MOVING SEWD ACROSS UPPER MS VALLEY THIS AFTERNOON. PRIMARY THREAT WILL BE HAIL/GUSTY WINDS. CLICK TO GET WUUS01 PTSDY1 PRODUCT NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 0100Z