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

   SPC AC 051239
   
   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0639 AM CST TUE FEB 05 2008
   
   VALID 051300Z - 061200Z
   
   ...THERE IS A HIGH RISK OF SVR TSTMS OVER A LARGE PORTION OF AR INTO
   FAR SWRN TN AND NWRN MS...
   
   ...THERE IS A MDT RISK OF SVR TSTMS SURROUNDING THE HIGH RISK BUT
   EXTENDING ENEWD INTO THE OH RIVER VALLEY AND TOWARDS THE TN RIVER
   VALLEY...
   
   ...THERE IS A SLGT RISK OF SVR TSTMS FROM PORTIONS OF THE SRN PLAINS
   ENEWD INTO THE OH/TN RIVER VALLEYS AND CENTRAL GULF COAST STATES...
   
   OVERALL SYNOPTIC SETUP WILL BECOME QUITE FAVORABLE FOR AN OUTBREAK
   OF SEVERE THUNDERSTORMS AND TORNADOES...INCLUDING LONG-LIVED
   TORNADIC SUPERCELLS...CENTERED ON THE MID SOUTH THIS AFTERNOON AND
   EVENING.  MAXIMUM SEVERE THREAT AREA SHOULD THEN SHIFT ACROSS THE
   NRN HALF OF THE GULF COAST STATES LATER TONIGHT.
   
   ...SYNOPSIS...
   DEEP UPPER LEVEL TROUGH AND ASSOCIATED EXTREME MID AND UPPER LEVEL
   WIND FIELDS /H5 JET MAX IN EXCESS OF 90 KT...130+ KT AT H25/ WILL
   SUSTAIN AN ENHANCED RISK OF SEVERE THUNDERSTORMS FROM THE SRN PLAINS
   INTO THE GULF COAST STATES/OH RIVER VALLEYS THROUGH THE PERIOD. 
   WIDESPREAD...ELEVATED THUNDERSTORMS CONTINUE TO INCREASE EARLY THIS
   MORNING ASSOCIATED WITH EJECTING LOWER AMPLITUDE WAVE FROM NRN TX
   ACROSS OK.  ADDITIONAL WIDESPREAD THUNDERSTORMS CONTINUE TO
   BACKBUILD/PERSIST WITHIN BROAD REGION OF LOW LEVEL WAA AND ENHANCED
   ASCENT NEAR SURFACE COLD FRONT PUSHING SLOWLY SWD OVER THE OH RIVER
   VALLEY.
   
   SURFACE LOW IS DEVELOPING OVER FAR NWRN TX AND IS FORECAST TO DEEPEN
   FURTHER AS IT LIFTS NEWD ALONG SURFACE FRONT INTO NRN AR BY LATE
   TODAY AND INTO SRN IND LATER TONIGHT.  AS UPPER SYSTEM EJECTS
   EWD...DRY LINE/N-S SURFACE TROUGH WILL BEGIN TO SURGE EWD ACROSS
   CENTRAL TX/OK THIS MORNING AND SHIFT STEADILY EAST ACROSS THE
   LOWER/MID MS RIVER VALLEYS TONIGHT. MEANWHILE...SURFACE FRONT
   TRAILING FAST MOVING SHORTWAVE TROUGH NOW MOVING ACROSS THE UPPER
   MIDWEST IS EXPECTED TO STALL AND THEN LIFT NWD SLIGHTLY LATE TONIGHT
   AS A WARM FRONT IN RESPONSE TO DEEPENING SURFACE LOW ACROSS THE
   LOWER OH RIVER VALLEY.  NET RESULT WILL BE PERSISTENT MOISTENING
   WITHIN BROAD WARM SECTOR FROM ERN TX INTO THE TN VALLEY THROUGH THE
   PERIOD...WITH SURFACE DEW POINTS AOA 60F EXTENDING AS FAR NORTH AS
   THE OH RIVER VALLEY.
   
   ...MID SOUTH INTO THE CENTRAL GULF COAST STATES...
   EXPECT ISOLATED SEVERE THUNDERSTORMS...INITIALLY ELEVATED...WILL
   PERSIST AS THEY SPREAD ENEWD AHEAD OF WEAKENING IMPULSES IN
   SUBTROPICAL JET STREAM. /REF LATEST SWOMCDS FOR NOWCASTS ACROSS THIS
   AREA/.  HOWEVER...ACTIVITY SHOULD BECOME INCREASINGLY SURFACE-BASED
   LATER THIS MORNING WITHIN EXTREME SHEAR AND VERY MOIST BOUNDARY
   LAYER INCREASING RISK OF ISOLATED TORNADOES/DAMAGING WINDS.  12Z
   SOUNDING FROM LZK AND MODIFIED OUN SOUNDING INDICATE MLCIN IS
   RELATIVELY WEAK ALREADY.  ONCE CAPPING BREAKS FROM ERN OK INTO NRN
   HALF OF AR/FAR SRN MO WITH THIS INITIAL WAVE...SEVERE THREAT SHOULD
   RAMP UP QUICKLY.
   
   APPEARS SRN/ERN AR INTO FAR NRN LA/WRN TN/NWRN MS WILL REMAIN
   RELATIVELY FREE OF MOIST CONVECTION THROUGH THE EARLY AFTERNOON...AS
   EARLY DAY ACTIVITY SHIFTS NEWD ACROSS THE OZARK PLATEAU/MO. 
   THUS...AS MAIN IMPULSE AND ASSOCIATED SURFACE FRONT SPREAD EWD LATE
   TODAY...ROBUST THUNDERSTORM DEVELOPMENT SHOULD ENSUE WITHIN MLCAPE
   AROUND 1000 J/KG AND WEAK CIN.  EXTREME SHEAR WITH SFC-1 KM SRH IN
   EXCESS OF 300 M2/S2 SUGGESTS STORMS WILL RAPIDLY DEVELOP ROTATION
   AND AN ATTENDANT TORNADO THREAT ONCE THEY ROOT INTO DEEPLY MOIST
   BOUNDARY LAYER.  ANY TORNADIC SUPERCELLS COULD PRODUCE A LONG-LIVED
   SIGNIFICANT TORNADO IN THIS ENVIRONMENT.  STORMS MAY TEND TO EVOLVE
   INTO A BROKEN SQUALL LINE LATE THIS EVENING AS FRONT INTERACTS WITH
   RICH GULF MOISTURE AND MOVES ACROSS THE GULF COAST STATES OVERNIGHT.
    DAMAGING WIND THREAT COULD ALSO BECOME WIDESPREAD GIVEN EXTREME
   WIND FIELDS JUST OFF THE SURFACE...ALTHOUGH THREAT FOR A SIGNIFICANT
   TORNADO WILL CONTINUE OVERNIGHT WITH LEWP AND PRE-SQUALL LINE
   DEVELOPMENT.
   
   ...LOWER OH/MID MS RIVER VALLEY ENEWD INTO KY/OH RIVER VALLEY...
   EARLY DAY ACTIVITY WILL CONTINUE TO POSE AN ISOLATED RISK OF SEVERE
   WITHIN WEAK INSTABILITY AND SMALL CAP FROM PORTIONS OF SERN MO INTO
   NRN KY/SWRN OH.  SHEAR WILL REMAIN MORE THAN ADEQUATE FOR
   SUPERCELLS...AND TORNADO THREAT MAY INCREASE THROUGH THE MORNING IF
   STORMS BEGIN ROOTING INTO THE BOUNDARY LAYER.  /REF UPCOMING
   SWOMCD/.  LATER TONIGHT...SEVERE THREAT SHOULD BECOME MORE ISOLATED
   IN NATURE WITH LOW CENTER SHIFTING UP THE OH RIVER VALLEY AND INTO
   KY LATER TONIGHT.  FORECAST SOUNDINGS INDICATE QUESTIONABLE
   SURFACE-BASED INSTABILITY.  HOWEVER...EXTREME SHEAR AND EFFECTIVE
   INFLOW TAPPING LOW/MID 60F SURFACE DEW POINTS WARRANTS PERSISTENT
   RISK OF ISOLATED STRONG TORNADOES AND/OR WIND DAMAGE.
   
   ..EVANS.. 02/05/2008
   
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   NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1630Z