SPC AC 100456 DAY 1 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 1156 PM CDT THU OCT 09 2014 VALID 101200Z - 111200Z ...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PORTIONS OF SOUTHERN OKLAHOMA AND NORTH TEXAS... ...SUMMARY... THUNDERSTORMS ARE EXPECTED FRIDAY FROM OKLAHOMA AND NORTHERN AND WESTERN TEXAS EASTWARD TO THE SOUTHERN APPALACHIANS. ISOLATED STRONG TO SEVERE STORMS CAPABLE OF WIND OR HAIL WILL BE POSSIBLE...MAINLY ACROSS THE SOUTHERN PLAINS AND THE TENNESSEE VALLEY. ...SYNOPSIS... A SPLIT FLOW REGIME WILL PERSIST ACROSS THE EASTERN TWO-THIRDS OF THE CONUS TODAY. IN THE NORTHERN STREAM...A BROAD TROUGH FROM THE UPPER MIDWEST TO NEW ENGLAND WILL AMPLIFY SLIGHTLY AS A SHORTWAVE IMPULSE MIGRATES SEWD FROM SASKATCHEWAN AND TRACKS ACROSS THE GREAT LAKES. TO THE SOUTHWEST IN THE SOUTHERN STREAM...A POSITIVELY TILTED SHORTWAVE TROUGH OVER THE SOUTHERN ROCKIES WILL SLOWLY MIGRATE EWD INTO THE SOUTHERN PLAINS. AT THE SFC...A COLD FRONT WILL STRETCH GENERALLY W-E FROM NEAR THE TX PANHANDLE/WRN OK INTO THE OHIO VALLEY AND THE CENTRAL APPALACHIANS. SCATTERED STORMS...SOME STRONG TO LOCALLY SEVERE...WILL BE POSSIBLE AHEAD OF THE COLD FRONT FROM THE SOUTHERN PLAINS INTO THE TN VALLEY. ...SOUTHERN PLAINS... WIDESPREAD THUNDERSTORMS ARE EXPECTED TO BE ONGOING ACROSS NE OK THIS MORNING IN A WARM ADVECTION REGIME ATOP THE STALLED SFC COLD FRONT. AS THE UPPER TROUGH BEGINS TO EJECT EWD BY AFTERNOON...THE COLD FRONT WILL BEGIN TO ADVANCE S/SE AND ADDITIONAL THUNDERSTORM DEVELOPMENT IS EXPECTED DURING THE AFTERNOON FROM SE OK SWWD INTO W TX. AHEAD OF THE FRONT...TEMPERATURES WARMING INTO THE LOW TO MID 80S AND DEWPOINTS GENERALLY IN THE MID 60S WILL RESULT IN MODERATE INSTABILITY /SBCAPE NEAR 1500-2000 J PER KG/. AS THE UPPER TROUGH SHIFTS EWD ACROSS NM INTO W TX...COOLING MIDLEVEL TEMPERATURES WILL LEAD TO ADEQUATE MIDLEVEL LAPSE RATES /7-7.5 DEG C PER KM/ FOR SEVERE HAIL. WHILE EFFECTIVE SHEAR WILL RANGE FROM AROUND 35-45 KT...WEAK LOW LEVEL FLOW WILL FAVOR OUTFLOW DOMINATED CELLS AND BOWING SEGMENTS...WITH SOME GUSTY/LOCALLY DAMAGING WINDS POSSIBLE. THE MOST FAVORABLE ZONE FOR SEVERE STORMS DUE TO BETTER JUXTAPOSITION OF STEEP LAPSE RATES AND GREATER INSTABILITY APPEARS TO BE FROM S-CNTRL/SE OK SWWD INTO N TX. A MORE MARGINAL WIND/HAIL THREAT MAY EXTEND FURTHER SOUTH INTO CENTRAL TX...BUT DEEP LAYER SHEAR WILL WEAKEN QUICKLY WITH SOUTHERN EXTENT AND CONVECTION WILL BECOME MORE ISOLATED UNTIL OVERNIGHT WHEN THE LLJ INCREASES. AS THE COLD FRONT TRACKS S/SE AND THE SWLY LLJ INCREASES OVERNIGHT...ELEVATED LINEAR CONVECTION WILL CONTINUE INTO PARTS OF CNTRL AND ERN TX...BUT SEVERE THREAT SHOULD DIMINISH WITH LOSS OF DAYTIME HEATING. ...TN VALLEY... ADDITIONAL STRONG STORMS...SOME POTENTIALLY SEVERE...WILL BE POSSIBLE ACROSS PARTS OF MIDDLE AND ERN TN AND VICINITY. DEEP LAYER SHEAR WILL INCREASE AHEAD OF THE PLAINS TROUGH AND ON THE SRN PERIPHERY OF THE DEEPENING GREAT LAKES SHORTWAVE. WHILE AMPLE LOW LEVEL MOISTURE WILL BE IN PLACE /DEWPOINTS IN THE MID 60S/...CLOUD COVER AND POSSIBLE MORNING CONVECTION LEADS TO UNCERTAINTY IN DEGREE OF AFTERNOON DESTABILIZATION TO THE SOUTH OF THE COLD FRONT. AT LEAST A CONDITIONAL THREAT FOR SOME HAIL AND WIND WILL EXIST...AND AN UPGRADE TO SLIGHT MAY BE NEEDED IN SUBSEQUENT OUTLOOKS IF CONFIDENCE INCREASES IN THE DEVELOPMENT OF MORE THAN ISOLATED STRONGER/ORGANIZED CONVECTION. ..LEITMAN/SMITH.. 10/10/2014
Posted on: Fri, 10 Oct 2014 11:56:56 +0000
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