SPC AC 050558
   
   DAY 2 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   1258 AM CDT TUE MAY 05 2009
   
   VALID 061200Z - 071200Z
   
   ...THERE IS A SLGT RISK OF SVR TSTMS ACROSS E TX/LOWER MS VALLEY TO
   SRN/CENTRAL APPALACHIANS...
   
   ...THERE IS A SLGT RISK OF SVR TSTMS ACROSS NRN MO/SRN IA INTO
   WRN/CENTRAL IL...
   
   ...SYNOPSIS...
   00Z DETERMINISTIC MODELS ARE IN BETTER AGREEMENT FOR THE DAY 2
   PERIOD /WED/ THAN INDICATED WITH THE PREVIOUS DAY 3 OUTLOOK FOR THIS
   SAME DAY.  A LEAD IMPULSE OR TWO WILL TRACK FROM THE MID SOUTH TO
   UPPER OH VALLEY DURING THE DAY WEDNESDAY WITHIN A BAND OF 50-60 KT
   SWLY MID LEVEL WINDS...FOLLOWED BY A LONGWAVE TROUGH PROGRESSING EWD
   FROM THE MS VALLEY TO SRN/CENTRAL APPALACHIANS.  MEANWHILE...FAST
   WNWLY MID/UPPER LEVEL FLOW WILL EXTEND FROM THE PACIFIC NW THROUGH
   THE CENTRAL PLAINS TO MID MS VALLEY...WHILE HEIGHTS RISE ACROSS THE
   SRN PLAINS.  A SHORTWAVE TROUGH...CURRENTLY TRACKING THROUGH WRN WA
   PER WATER VAPOR IMAGERY...IS EXPECTED TO MOVE EWD ALONG AND JUST N
   OF THE U.S./CANADIAN BORDER...REACHING SRN MANITOBA BY 12Z THURSDAY.
   
   ...E TX/LOWER MS VALLEY NEWD TO SRN AND CENTRAL APPALACHIANS...
   MODELS SUGGEST A COUPLE OF CONVECTIVE COMPLEXES/MCS/S WILL BE
   ONGOING AT 12Z WEDNESDAY FROM THE RED RIVER VALLEY THROUGH AR TO
   MUCH OF TN. THE GREATEST AMOUNT OF DESTABILIZATION IS EXPECTED TO
   OCCUR ALONG AND S OF THIS ONGOING ACTIVITY FROM E TX/LOWER MS VALLEY
   INTO THE CENTRAL GULF COAST STATES.  THE STRONGEST SWLY LLJ IS
   EXPECTED TO TRANSLATE NEWD THROUGH THE TN VALLEY TO UPPER OH
   VALLEY/CENTRAL APPALACHIANS.  HOWEVER...THE LINGERING SRN PORTION OF
   THIS JET AND SECOND LLJ ATTENDANT TO WRN MCS SHOULD SUPPORT
   SUFFICIENT SHEAR FOR SEVERE STORMS FROM E TX TO LOWER MS VALLEY AS
   ONGOING MORNING ACTIVITY SPREADS ESEWD INTO THESE AREAS.
   
   FARTHER NE...EFFECTIVE BULK SHEAR WILL INCREASE THROUGH THE
   DAY...BUT WEAK INSTABILITY MAY TEND TO LIMIT THE OVERALL SEVERE
   WEATHER THREAT ACROSS PARTS OF THE TN VALLEY TO CENTRAL/SRN
   APPALACHIANS.  THIS OUTLOOK WILL MAINTAIN A SLIGHT RISK INTO THESE
   AREAS...GIVEN THE STRENGTH OF THE LOW LEVEL WIND FIELDS SUPPORTING A
   DAMAGING WIND THREAT.
   
   ...LOWER MO/MID-UPPER MS VALLEYS...
   A SURFACE TROUGH...ACCOMPANYING THE WA SHORTWAVE TROUGH...IS
   EXPECTED TO MOVE EWD FROM THE NRN/CENTRAL PLAINS AND SHOULD EXTEND
   SSWWD FROM WRN MN TO SERN NEB/ERN KS BY LATE WEDNESDAY AFTERNOON. 
   SWLY LOW LEVEL WINDS EXTENDING FROM THE SRN PLAINS TO MO WILL
   SUPPORT MOISTURE RETURN WITH SURFACE DEWPOINTS IN THE LOWER-MID 60S
   REACHING THE LOWER MO RIVER VALLEY BY LATE AFTERNOON.  MID-UPPER 50S
   DEWPOINTS SHOULD EXTEND INTO MUCH OF IA TO CENTRAL IL.  ERN EXTENT
   OF STEEP MID LEVEL LAPSE RATES WILL SPREAD EWD ACROSS WRN IA AND MO.
   THIS COMBINED WITH SURFACE HEATING WILL SUPPORT MODERATE INSTABILITY
   ACROSS MUCH OF MO INTO FAR SRN IA.  MODELS SUGGEST TSTMS MAY BE
   ONGOING ACROSS ERN NEB/WRN IA AT 12Z WEDNESDAY...WITH ADDITIONAL
   TSTM DEVELOPMENT BY AFTERNOON FROM THE UPPER MS VALLEY SWD TO NRN
   MO.  THESE AREAS WILL BE LOCATED WITHIN THE EXIT REGION OF A 100+ KT
   UPPER LEVEL JET.  THE STRONGEST STORMS SHOULD BE LOCATED ACROSS FAR
   SRN IA INTO NRN MO IN THE VICINITY OF A SURFACE FRONT EXTENDING SEWD
   FROM SRN IA TO ALONG THE MO/IL BORDER.  INCREASING EFFECTIVE BULK
   SHEAR /40-50 KT/ ATTENDANT TO 50 KT NWLY MID LEVEL JET NOSING INTO
   THIS REGION WILL SUPPORT ORGANIZED STORMS/SUPERCELLS.  AN INCREASING
   AND VEERING LLJ WEDNESDAY EVENING SHOULD SUPPORT A CLUSTER OF TSTMS
   SPREADING INTO CENTRAL IL WITH AN ATTENDANT THREAT FOR AT LEAST
   ISOLATED SEVERE STORMS.  
   
   FARTHER N...WEAKER INSTABILITY /MLCAPE AROUND 500 J/KG/ AND MODEST
   EFFECTIVE BULK SHEAR /25-30 KT/ SUGGEST A MORE ISOLATED THREAT FOR
   SEVERE STORMS NWD ACROSS ERN MN/WI AHEAD OF THE EWD MOVING N-S
   ORIENTED SURFACE TROUGH.
   
   ...CENTRAL TX TO PART OF N TX AND ADJACENT SRN OK...
   A MODERATELY TO VERY UNSTABLE AIR MASS IS EXPECTED ACROSS THIS
   REGION WEDNESDAY AFTERNOON WITH EFFECTIVE BULK SHEAR MORE THAN
   ADEQUATE FOR ORGANIZED STORMS/SUPERCELLS.  HOWEVER...GIVEN HEIGHT
   RISES/WARMING MID LEVEL TEMPERATURES...A STRONG CAP WILL TEND TO
   LIMIT THE DEVELOPMENT OF WIDESPREAD TSTMS.  MODELS SUGGEST ISOLATED
   STORMS WILL BE POSSIBLE...BUT GIVEN THE POTENTIAL FOR LOWER TSTM
   COVERAGE...THIS OUTLOOK WILL NOT INCLUDE A SLIGHT RISK YET FOR THIS
   REGION. 
   
   ...CENTRAL PLAINS WEDNESDAY NIGHT...
   A SLY NOCTURNAL LLJ WILL DEVELOP WEDNESDAY NIGHT ACROSS THE SRN/
   CENTRAL HIGH PLAINS AND VEER TO SWLY OVERNIGHT WITH THE APPROACH OF
   A WEAK MID LEVEL IMPULSE TO THE CENTRAL PLAINS BY 12Z THURSDAY. 
   INCREASING LOW LEVEL WAA INTO THE CENTRAL PLAINS WILL SUPPORT
   SCATTERED ELEVATED TSTM DEVELOPMENT...WITH SOME HAIL THREAT AS
   EFFECTIVE BULK SHEAR INCREASES AND MUCAPE RANGES FROM 500-1000 J/KG.
   
   ..PETERS.. 05/05/2009
   
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   NOTE: THE NEXT DAY 2 OUTLOOK IS SCHEDULED BY 1730Z