SPC AC 231258

   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0658 AM CST TUE DEC 23 2014

   VALID 231300Z - 241200Z

   ...THERE IS A SLGT RISK OF SVR TSTMS PORTIONS SRN/ERN
   LA...MS...AL...FL PANHANDLE...SWRN GA...

   ...THERE IS A MRGL RISK OF SVR TSTMS ELSEWHERE FROM SE TX TO SRN
   SC...

   ...SUMMARY...
   SPORADIC STRONG TO SEVERE THUNDERSTORMS ARE EXPECTED TODAY AND
   TONIGHT ACROSS A BROAD SWATH OF DIXIE...FROM LOUISIANA TO ALABAMA
   AND THE FLORIDA PANHANDLE.  ISOLATED SEVERE HAIL OR STRONG GUSTS MAY
   OCCUR FARTHER EAST ACROSS PARTS OF GEORGIA AND SOUTHERN SOUTH
   CAROLINA...AND FARTHER WEST INTO EXTREME SOUTHEAST TEXAS.

   ...SYNOPSIS...
   IN MID-UPPER LEVELS...DEEP SYNOPTIC TROUGHING AND ASSOCIATED
   CYCLONIC FLOW WILL REMAIN ENTRENCHED OVER CENTRAL CONUS...THOUGH ITS
   GEOMETRY WILL BE ALTERED ON MESOSCALE BY SEVERAL SHORTWAVE
   PERTURBATIONS...FIRST OF WHICH IS REPRESENTED BY 500-MB CYCLONE NOW
   CENTERED OVER SWRN IA.  THIS LOW WILL WEAKEN INTO OPEN-WAVE
   CONFIGURATION WHILE EJECTING NEWD ACROSS LS TO NERN ONT. 
   MEANWHILE...BASAL SHORTWAVE TROUGH AND RELATED VORTICITY BANNER --
   NOW EVIDENT OVER PARTS OF SRN NM AND W TX -- WILL PIVOT SEWD ACROSS
   SW/CENTRAL TX THROUGH 00Z...THEN ACROSS ARKLATEX AND SE/S-CENTRAL TX
   BY 12Z.

   RELATED SWATHS OF LARGE-SCALE DCVA/ASCENT SHOULD REMAIN MOSTLY
   BEHIND PRIMARY SFC COLD FRONT -- LOCATED AT 12Z FROM S-CENTRAL/SE TX
   NEWD ACROSS SERN AR. SECONDARY COLD SURGE ASSOCIATED WITH W TX/NM
   SHORTWAVE TROUGH WILL OVERTAKE THAT FRONT TODAY. COMBINED BOUNDARY
   SHOULD REACH WRN TN...W-CENTRAL MS...AND S-CENTRAL LA BY 00Z...WITH
   WEAK FRONTAL-WAVE LOW REACHING NERN MS OR MID TN BY 06Z.  AROUND END
   OF PERIOD...COLD FRONT SHOULD EXTEND FROM DEEPENING LOW OVER ERN
   INDIANA/WRN OH REGION...SWD ACROSS NWRN GA...THEN SSWWD OVER FL
   PANHANDLE TO S-CENTRAL/SWRN GULF.

   SFC WARM FRONTS ARE MANIFEST PRIMARILY BY TWO THETA GRADIENTS...
   1. INLAND/SYNOPTIC BOUNDARY EXTENDING FROM E-CENTRAL MS SEWD ACROSS
   SRN AL AND WRN FL PANHANDLE.
   2. MARINE FRONT...DEMARCATING NRN FRINGE OF OPTIMALLY MODIFIED GULF
   BOUNDARY-LAYER...AND LOCATED INITIALLY FROM TX SHELF WATERS ENEWD
   ACROSS MS RIVER MOUTH TO NEAR PNS BEACH...THEN SEWD ACROSS NERN GULF
   TO TBW AREA.  EACH BOUNDARY SHOULD REMAIN SHALLOW AND DRIFT NNEWD
   AHEAD OF SFC COLD FRONT...WITH RELATED THETAE ADVECTION CAUSING AT
   LEAST MRGLLY SFC-BASED EFFECTIVE INFLOW PARCELS TO EXTEND INLAND
   OVER OUTLOOK AREA.  ONGOING PRECIP/CONVECTION WILL DELAY RETURN OF
   MOST FAVORABLE AIR OVER ERN AL AND GA...PERHAPS ALSO FRAGMENTING
   THAT LEADING FRONTAL ZONE THERE.

   ...DEEP SOUTH...
   FOR MOST OF TODAY...SCATTERED TO WIDELY SCATTERED TSTMS ARE EXPECTED
   ON ALL SIDES OF WARM-FRONTAL ZONES AND ALONG/AHEAD OF COLD FRONT. 
   DAMAGING GUSTS...SPORADIC HAIL AND A FEW TORNADOES ARE MOST PROBABLE
   OVER GULF COASTAL PLAIN AND LOWER DELTA.  SQUALL LINE SHOULD DEVELOP
   GRADUALLY TONIGHT...ALONG OR JUST AHEAD OF SFC COLD FRONT...AND MOVE
   EWD ACROSS AL/GA/FL PANHANDLE...OFFERING RISK OF DAMAGING GUSTS AND
   BRIEF/WEAK QLCS TORNADO.

   MORNING LIX/LCH RAOBS INDICATED RELATIVELY STEEP MIDLEVEL LAPSE
   RATES WITH UNDERLYING STABLE LAYER.  THIS REPRESENTS REMNANTS OF EML
   SAMPLED ROBUSTLY IN CRP/BRO RAOBS AND ADVECTED FROM MEX PLATEAU. 
   THIS WILL AUGMENT BUOYANCY -- WHETHER SFC-BASED OR ELEVATED -- OVER
   DELTA REGION.  ALONG WITH FAVORABLE SHEAR FOR SUPERCELLS...THIS WILL
   CONTRIBUTE TO RELATIVELY MAXIMIZED POTENTIAL FOR SVR
   HAIL...ESPECIALLY WITH ANY RELATIVELY SUSTAINED/DISCRETE CELLS.

   FARTHER E...DEEP FETCH OF MID-UPPER-LEVEL MOISTURE FROM TROPICAL ERN
   PAC -- NOW EVIDENT IN MOISTURE-CHANNEL IMAGERY -- WILL CONTINUE TO
   STREAM ACROSS CENTRAL GULF COAST...AL AND GA.  ALONG WITH LAG OF
   MID-UPPER-LEVEL LIFT BEHIND COLD FRONT...THIS CLOUD PLUME WILL
   DIRECTLY LIMIT LAPSE RATES ALOFT...AND INDIRECTLY IN LOW LEVELS
   THROUGH REDUCTION OF DIURNAL SFC HEATING.  AS SUCH...CAPE SHOULD
   REMAIN WEAK ACROSS MUCH OF OUTLOOK AREA AWAY FROM GULF COAST...WHERE
   SFC DEW POINTS UPPER 60S TO LOW 70S F AND ASSOCIATED THETAE WILL
   OFFSET THOSE POOR LAPSE RATES TO YIELD MLCAPE AROUND 1000-1500 J/KG.
    IN GENERAL...BUOYANCY WILL DIMINISH WITH INLAND EXTENT...AS PEAK
   MLCAPE STAYS LESS THAN 250 J/KG ACROSS MOST OF MID-SOUTH AND TN
   VALLEY...AS WELL AS INVOF RECENT AREAS OF CONVECTIVE OUTFLOW.

   HOWEVER...FAVORABLE AND STEADILY INCREASING DEEP SHEAR WILL
   JUXTAPOSE WITH WARM SECTOR WHILE EFFECTIVE SRH MAXIMIZES IN 200-350
   J/KG RANGE INVOF WARM-FRONTAL SEGMENTS.  CELLS INTERACTING WITH
   THESE BOUNDARIES SHOULD OFFER RELATIVELY MAXIMIZED POTENTIAL FOR
   MESOCYCLONE INTENSIFICATION AND POSSIBLY TORNADOES.

   ..EDWARDS/COHEN.. 12/23/2014

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