SPC AC 241256 DAY 1 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 0656 AM CST WED DEC 24 2014 VALID 241300Z - 251200Z ...THERE IS A SLGT RISK OF SVR TSTMS FL COASTAL BEND TO ERN SC... ...THERE IS A MRGL RISK OF SVR TSTMS ELSEWHERE FROM CENTRAL/NRN FL TO HAMPTON ROADS AREA... ...THERE IS A MRGL RISK OF SVR TSTMS PORTIONS ERN KY/WV TO LE... ...SUMMARY... SCATTERED THUNDERSTORMS...A FEW OFFERING DAMAGING GUSTS AND A RISK OF A TORNADO...WILL MOVE EASTWARD AND NORTHEASTWARD ACROSS PARTS OF FLORIDA...GEORGIA AND THE CAROLINAS...PERHAPS AS FAR NORTHEAST AS THE HAMPTON ROADS REGION OF VIRGINIA. SHOWERS AND THUNDERSTORMS ALSO MAY SPAWN GUSTS APPROACHING SEVERE LEVELS TODAY FROM PARTS OF EASTERN KENTUCKY AND WEST VIRGINIA NORTHWARD TO LAKE ERIE. ...SYNOPSIS... HIGHLY AMPLIFIED...YET PROGRESSIVE...UPPER-AIR PATTERN WILL EXIST OVER CONUS THIS PERIOD. POSITIVELY TILTED TROUGH -- INITIALLY LOCATED FROM UPPER MS VALLEY TO SWRN MO...ARKLATEX AND COAHUILA -- WILL MOVE EWD AT FIRST. BY 00Z...TROUGH SHOULD BE LOCATED NEAR AN MQT...ORD...MEM...BPT...BRO LINE. BY 12Z...TROUGH SHOULD EXTEND FROM CLOSED 500-MB LOW OVER SWRN QUE...SSWWD NEAR BUF...CRW...ATL...MOB AND OVER NWRN GULF. AT SFC...CYCLONE OVER NRN KY WILL CONTINUE TO DEEPEN AND MOVE NNEWD...REACHING DTW AREA BY 00Z...WHEN SFC COLD FRONT SHOULD ARC SEWD THEN SWD ACROSS WV...WRN CAROLINAS...CENTRAL/ERN GA AND NWRN FL. BY END OF PERIOD...SFC LOW SHOULD BE OCCLUDED AND STACKED WITH 500-MB LOW OVER SWRN QUE. SFC COLD FRONT WILL SWEEP OFFSHORE ATLC COAST...EXCEPT FOR ERN NEW ENGLAND AND SRN FL...BY 12Z. ...SERN CONUS... SQUALL LINE IS BECOMING MORE DEFINED ATTM FROM W-CENTRAL FL PANHANDLE NEWD OVER GA...AHEAD OF SFC COLD FRONT...AND WILL OFFER RISK OF SPORADIC DAMAGING GUSTS AND A QLCS TORNADO OR TWO THROUGH AT LEAST MIDDAY. MEANWHILE...FOREGOING WARM SECTOR AND ITS CHARACTERISTIC LOW-CAPE/HIGH-SHEAR PARAMETER SPACE WILL EXPAND NEWD ACROSS REMAINDER SERN GA AND SRN SC...AHEAD OF STABILIZING EFFECTS OF PRECIP SHIELD THAT EXTENDS NEWD FROM SQUALL LINE. MODEST DIURNAL DESTABILIZATION AND SFC THETAE ADVECTION WILL COMBINE TO YIELD SFC-BASED EFFECTIVE-INFLOW PARCELS...AND MLCAPE GENERALLY AOB 500 J/KG...JUXTAPOSED WITH 50-60 KT EFFECTIVE-SHEAR MAGNITUDES AND POCKETS OF 200-400 J/KG EFFECTIVE SRH. AS SUCH...A COUPLE TORNADOES CANNOT BE RULED OUT WITH ENLARGED LOW-LEVEL HODOGRAPHS AND MRGL BUOYANCY DEVELOPING ALONG AND S OF RETREATING DAMMING FRONT. LOW-LEVEL HODOGRAPHS SHOULD REMAIN ELONGATED BUT BECOME LESS CURVED WITH TIME TODAY AS SFC FLOW VEERS ACROSS OUTLOOK AREA...WITH MIDLEVEL WINDS BEING NEARLY PARALLEL TO ALIGNMENT OF CONVECTIVE BANDS. AS SUCH...LINEAR MODE WILL BE MORE PREVALENT WITH TIME. REF WW 563 AND RELATED MESOSCALE DISCUSSIONS FOR COVERAGE OF NEAR-TERM SVR THREAT OVER PORTIONS GA...NWRN FL AND SRN SC. ...PORTIONS ERN KY/WV TO LE... BAND OF LOW-TOPPED CONVECTION MAY DEVELOP OVER PORTIONS WRN OH AND NRN KY THIS AFTN...ALONG/AHEAD OF COLD FRONT AND SE OF SFC LOW. ALTHOUGH MUCH OF THIS ACTIVITY MAY BE TOO SHALLOW TO PRODUCE LTG...AT LEAST ISOLATED TSTMS ARE POSSIBLE...AND GUSTS APCHG SVR LIMITS WILL BE POSSIBLE REGARDLESS OF ELECTRICAL CHARACTERISTICS. THREAT APPEARS TOO LOW/CONDITIONAL TO DRAW MORE THAN MRGL PROBABILITIES ATTM. INTENSE DEEP-LAYER WINDS WILL BE MAINTAINED ACROSS THIS AREA THROUGH AFTN AS FORCED ASCENT BUILDS NEWD-MOVING CONVECTIVE BAND WITH TOPS LARGELY UNDER 20 KFT. MAIN LIMITING FACTOR WILL BE LACK OF INSTABILITY. EXPECT MIDTROPOSPHERIC LAPSE RATES ONLY SLIGHTLY GREATER THAN MOIST-NEUTRAL...MUCAPE UNDER 300 J/KG IN MOST AREAS AND POTENTIAL FOR SHALLOW/STABLE BOUNDARY LAYER TO KEEP BULK OF INFLOW PARCELS SLIGHTLY ELEVATED. AS SUCH...WIND ENHANCEMENT OF DOWNDRAFTS ASSOCIATED WITH DOWNWARD MOMENTUM TRANSFER WILL BE COUNTERACTED BY SFC STATIC STABILITY IN MOST AREAS. HOWEVER...VERY NARROW CORRIDOR OF PRECONVECTIVE BUOYANCY MAY SUPPORT A FEW STRONG GUSTS THAT MAY REACH SFC...WITH MINOR DAMAGE POSSIBLE. ..EDWARDS/COHEN.. 12/24/2014
Posted on: Wed, 24 Dec 2014 13:56:13 +0000
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