Categorical Graphic
Probabilistic Tornado Graphic
Probabilistic Damaging Wind Graphic
Probabilistic Large Hail Graphic

   SPC AC 240557
   
   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   1257 AM CDT SAT APR 24 2010
   
   VALID 241200Z - 251200Z
   
   ...THERE IS A HIGH RISK OF SVR TSTMS PORTIONS SERN AR...NERN
   LA...MS...CENTRAL/NRN AL...
   
   ...THERE IS A MDT RISK OF SVR TSTMS ELSEWHERE FROM PORTIONS E TX TO
   CENTRAL/NRN LA...AL...WRN GA...TN...SRN/CENTRAL KY...EXTREME SERN
   MO...CENTRAL/SRN/ERN AR....
   
   ...THERE IS A SLGT RISK OF SVR TSTMS SURROUNDING MDT RISK...FROM
   GULF COAST OF SE TX TO FL PANHANDLE...TO PORTIONS WV/OH...TO
   PORTIONS LOWER MO VALLEY REGION...TO E TX....
   
   OUTBREAK OF NUMEROUS SVR TSTMS IS EXPECTED TODAY...GREATEST
   CONCENTRATION/INTENSITY OF WHICH SHOULD INCLUDE STG-VIOLENT TORNADO
   THREAT AFFECTING MID-SOUTH...MS DELTA REGION...AND TN VALLEY.  
   
   ...SYNOPSIS...
   SPLIT-FLOW PATTERN IN MID-UPPER LEVELS FEATURES CYCLONE INITIALLY
   LOCATED OVER CENTRAL HIGH PLAINS...FCST TO MOVE EWD ACROSS KS TO WRN
   MO BY 25/00Z AND WEAKEN ALONG WITH ITS SFC MANIFESTATION. 
   MEANWHILE...STG SHORTWAVE TROUGH AND SPEED MAX ALOFT -- WHICH
   COMPRISED MOST OF INITIAL UPPER CYCLONE OVER SWRN CONUS DURING
   PREVIOUS FEW DAYS -- IS FCST TO EJECT NEWD FROM CENTRAL TX TO ERN
   MO/SRN IL AREA BY 25/00Z...TAKING OVER AGAIN AS PRIMARY 500 MB LOW. 
   BY THAT TIME...CORRESPONDING SFC CYCLONE WILL FORM ALONG OCCLUSION
   TRIPLE POINT E OF ORIGINAL...AND CLOSE TO NEWER MID-UPPER CYCLONE
   CENTER.  THIS PROCESS WILL RESULT IN REINFORCEMENT/ACCELERATION OF
   INITIALLY STALLED FRONTAL SEGMENT NOW OVER SWRN/CENTRAL TX NNEWD
   OVER ERN OK.  FRONT SHOULD MOVE ACROSS MUCH OF LA...WRN MS AND WRN
   PORTIONS TN/KY BY 25/00Z...TO FL PANHANDLE...AL...MIDDLE-ERN TN AND
   ERN KY BY END OF PERIOD....WHEN MID-UPPER CYCLONE SHOULD BE OVER NRN
   PORTIONS IL/INDIANA...AND SRN LM AREA. 
   
   ...LOWER MS VALLEY...MID-SOUTH AND TN VALLEY REGIONS...
   TSTMS SHOULD BE INCREASING IN COVERAGE/INTENSITY AROUND BEGINNING OF
   PERIOD OVER E TX...LA AND ARKLATEX REGION.  FOREGOING AIR MASS --
   ALREADY MOISTENED/DESTABILIZED FAVORABLY BY PRIOR/OVERNIGHT THETAE
   ADVECTION...WILL FURTHER DESTABILIZE AMIDST SFC DIABATIC HEATING. 
   AMOUNT OF HEATING IS SOMEWHAT IN QUESTION BECAUSE OF POTENTIAL FOR
   CLOUD/ANVIL DEBRIS SPREADING DOWNSTREAM IN MID-UPPER LEVELS FROM
   EARLY CONVECTION...PERHAPS INCLUDING TEMPORAL EXTENSION OF ACTIVITY
   NOW OVER S TX.  STILL...AWAY FROM EXISTING CONVECTION...EVERY
   REASONABLE SCENARIO INDICATES THAT MLCINH GENERALLY WILL WEAKEN WITH
   NWD EXTENT FROM GULF COAST...SUPPORTING EARLY AND RAPID DEVELOPMENT
   AND INTENSIFICATION OF TSTMS FROM MID-MORNING THROUGH
   MID-AFTERNOON...AND SUSTAINED THREAT SHIFTING EWD AND NEWD ACROSS
   OUTLOOK AREA INTO EVENING/OVERNIGHT HOURS.  
   
   INTENSE VERTICAL WIND PROFILES WILL SPREAD ACROSS BROAD WARM/MOIST
   SECTOR TODAY...MUCH OF WHICH ALREADY IS IN PLACE ACROSS MUCH OF
   LA...MS AND COASTAL AL.  THIS AIR MASS WILL SPREAD INLAND TOWARD TN
   VALLEY AS CONVECTION/PRECIP NOW OVER TN/AL/GA SHIFTS NEWD.  SFC DEW
   POINTS WILL BE 70S INVOF GULF COAST...TRANSITIONING TO UPPER 60S AS
   FAR N AS TN AND LOW-MID 60S TO OH VALLEY. WEAKENING LAPSE RATES
   ALOFT AND BUOYANCY WITH NWD EXTENT...FROM TN VALLEY TO OH VALLEY AND
   GREAT LAKES...RENDER PROGRESSIVELY MORE CONDITIONAL NATURE TO SVR
   THREAT...THOUGH KINEMATIC PROFILES WILL BECOME FAVORABLE OVER VERY
   LARGE AREA S OF GREAT LAKES BY EVENING/OVERNIGHT HOURS. 
   
   MULTIPLE CONVECTIVE EPISODES AND STORM MODES ARE EXPECTED IN THIS
   SITUATION...AGGREGATE OF WHICH SHOULD YIELD DENSE CONCENTRATION OF
   SVR EVENTS BY END OF PERIOD ACROSS MDT/HIGH CATEGORICAL RISK AREAS. 
   THOUGH DISCRETE/CYCLIC TORNADIC SUPERCELLS ARE MOST POTENTIALLY
   DANGEROUS THREAT...ESPECIALLY OVER HIGH RISK AREA...CLUSTERED AND
   QUASI-LINEAR CONVECTIVE ELEMENTS WITH EMBEDDED BOW/LEWP FORMATIONS
   AND SUPERCELLS ALSO APPEAR PROBABLE.  STRENGTHENING DEEP-LAYER WINDS
   AND RELATED FAST STORM MOTIONS PORTEND LONG TRACKS FOR SUPERCELLS
   AND FOR SOME OF THEIR TORNADOES...AS WELL AS FOR SWATHS OF DAMAGING
   WIND WITH ANY BOW/LEWP FEATURES.  THIS SUPPORTS RATHER ROBUST
   PROBABILITIES FOR ALL SEVERE MODES.  
   
   PARAMETER SPACES IN FCST SOUNDINGS OVER HIGH RISK AREA -- SHIFTING
   NEWD FROM LATE MORNING THROUGH AFTERNOON -- INCLUDE 50-60 KT LLJ
   SUPPORTING VERY LARGE HODOGRAPHS WITH 0-1 AND 0-1 KM SRH 300-600
   J/KG.  ALSO EXPECT 50-60 KT EFFECTIVE SHEAR MAGNITUDES BENEATH
   110-140 KT 250 MB JET MAX AND 60-90 KT 500 MB WINDS...POTENTIALLY
   JUXTAPOSED WITH MLCAPE 1500-2500 J/KG.  
   
   SUPERCELL/TORNADO THREAT MAY CARRY INTO EVENING/OVERNIGHT HOURS OVER
   CENTRAL/SRN APPALACHIANS REGION AND WRN GA BEFORE DIMINISHING. 
   
   ...IA...MO VALLEY REGION...
   SCATTERED STG-SVR TSTMS ARE EXPECTED TO DEVELOP ACROSS THIS AREA
   INVOF LARGE CYCLONE ALOFT...AS STEEP MID-UPPER LEVEL LAPSE RATES
   COLLOCATED WITH BROAD AREA OF LOW-LEVEL CONVERGENCE AND
   DIABATIC/DIURNAL DESTABILIZATION  OF BOUNDARY LAYER.  MAIN CONCERN
   WILL BE SVR HAIL...THOUGH POTENTIAL FOR DAMAGING GUSTS EXISTS.  SVR
   POTENTIAL SHOULD WANE SIGNIFICANTLY AFTER SUNSET.
   
   ..EDWARDS/GARNER.. 04/24/2010
   
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