Categorical Graphic
Probabilistic Graphic
Probability of severe weather within 25 miles of a point. Hatched Area: 10% or greater probability of significant severe within 25 miles of a point.

   SPC AC 211711
   
   DAY 2 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   1211 PM CDT THU APR 21 2011
   
   VALID 221200Z - 231200Z
   
   ...THERE IS A SLGT RISK OF SVR TSTMS FROM NWRN TX/OK INTO THE OH
   VALLEY...
   
   ...SRN PLAINS TO OH VALLEY...
   
   STRONG SHORTWAVE TROUGH AND ASSOCIATED MID LEVEL SPEED MAX WILL
   EJECT ACROSS THE CNTRL ROCKIES/PLAINS INTO THE UPPER GREAT LAKES
   REGION FRIDAY.  THIS LARGE SCALE FLOW REGIME WILL UNDOUBTEDLY
   ENHANCE LOW LEVEL WARM ADVECTION/MOISTENING BENEATH AN INTENSIFYING
   AND NEWD EVOLVING LLJ AS IT SHIFTS FROM ERN KS/OK EARLY IN THE
   PERIOD INTO IL/IND BY 23/00Z.  THIS FEATURE WILL FORCE A SUBSTANTIAL
   AMOUNT OF ELEVATED CONVECTION ALONG/NORTH OF RETREATING WARM FRONT
   THE ENTIRE FORECAST CYCLE...INITIALLY ALONG/NORTH OF THE I-70
   CORRIDOR BEFORE HEIGHT FALLS ALOFT INDUCE LARGE SCALE ASCENT TO
   OVERSPREAD THE GREAT LAKES/UPPER OH VALLEY.
   
   GIVEN THE VERY STEEP LAPSE RATES THAT REMAIN IN PLACE WEST OF THE MS
   RIVER...ANY ELEVATED STORMS THAT DEVELOP ATOP COOLER AIRMASS WOULD
   POSE AT LEAST A THREAT FOR LARGE HAIL.  OF MORE CONCERN WILL BE THE
   POSSIBILITY FOR SFC BASED CONVECTIVE DEVELOPMENT ALONG/AHEAD OF THE
   COLD FRONT ACROSS MO INTO IL/IND.  SUBSTANTIAL
   MOISTENING/DESTABILIZING IS EXPECTED ACROSS THIS REGION BY 18Z AND
   LATEST INDICATIONS ARE THAT MODEST INSTABILITY WILL BE IN PLACE BY
   MID AFTERNOON FOR ROBUST THUNDERSTORM DEVELOPMENT ACROSS MO WITHIN A
   STRONGLY SHEARED ENVIRONMENT FOR SUPERCELLS...INCLUDING THE
   POSSIBILITY FOR A FEW TORNADOES...VERY LARGE HAIL AND DAMAGING
   WINDS.  THIS ACTIVITY SHOULD SPREAD DOWNSTREAM INTO THE LOWER OH
   VALLEY INTO A RECOVERING AIRMASS IN THE WAKE OF NWD SHIFTING WARM
   FRONT.
   
   FARTHER SW...SFC FRONT WILL EASE SWD ACROSS NRN OK TO A POSITION
   ALONG I-44 FROM NE-SW ACROSS OK BY 23/00Z.  ALTHOUGH LARGE SCALE
   FORCING WILL PROVE NEGLIGIBLE ACROSS THE SRN PLAINS...INTENSE
   BOUNDARY LAYER HEATING WEST OF THE DRYLINE WILL LIKELY REMOVE THE
   CAP BY 21-22Z.  DEEP LAYER SHEAR IS EXPECTED TO BE ON THE ORDER OF
   45KT NEAR THE DRYLINE/COLD FRONT INTERSECTION WHERE SBCAPE VALUES
   SHOULD BE AOA 3500 J/KG.  LATEST THINKING IS SCATTERED SUPERCELLS
   WILL DEVELOP ALONG THE FRONT/DRYLINE WITHIN AN ENVIRONMENT CONDUCIVE
   FOR VERY LARGE HAIL AND POSSIBLY EVEN AN ISOLATED TORNADO.  THIS
   ACTIVITY IS EXPECTED TO PROPAGATE EWD ACROSS THE REMAINDER OF OK
   INTO LATE EVENING AS THE LLJ INCREASES AND VEERS TOWARD NRN AR.  SWD
   EXTENT OF AFTERNOON STORMS INTO NWRN TX IS POSSIBLE...BUT WITH WEAK
   SHEAR/CONVERGENCE THIS ACTIVITY WILL REMAIN ISOLATED.
   
   ..DARROW.. 04/21/2011
   
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   NOTE: THE NEXT DAY 2 OUTLOOK IS SCHEDULED BY 0600Z