Categorical Graphic
Probabilistic Tornado Graphic
Probability of a tornado within 25 miles of a point. Hatched Area: 10% or greater probability of EF2 - EF5 tornadoes within 25 miles of a point.
Probabilistic Damaging Wind Graphic
Probability of damaging thunderstorm winds or wind gusts of 50 knots or higher within 25 miles of a point. Hatched Area: 10% of greater probability of wind gusts 65 knots or greater within 25 miles of a point.
Probabilistic Large Hail Graphic
Probability of hail 1" or larger within 25 miles of a point. Hatched Area: 10% or greater probability of hail 2" or larger within 25 miles of a point.

   SPC AC 231623
   
   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   1123 AM CDT TUE AUG 23 2011
   
   VALID 231630Z - 241200Z
   
   ...THERE IS A SLGT RISK OF SVR TSTMS THIS AFTERNOON INTO TONIGHT FOR
   PARTS OF THE UPPER MS VALLEY TO LAKE MI AREA...
   
   ...UPPER MS VALLEY/LAKE MI AREA THROUGH TONIGHT...
   A PRONOUNCED MIDLEVEL SHORTWAVE TROUGH IS MOVING ESEWD OVER MN/WRN
   WI/NRN IA THIS MORNING.  THE WAVE IS PRECEDED BY AN MCV OVER CENTRAL
   WI...AND THE WEAKENING REMNANTS OF THE OVERNIGHT MCS/S ACROSS ERN
   IA/SRN WI/NRN IL.  THE ONGOING IA/IL CONVECTION MAY PERSIST FOR
   ANOTHER COUPLE OF HOURS INTO EARLY AFTERNOON IN ASSOCIATION WITH
   LOW-LEVEL WAA ALONG THE AXIS OF A 30-35 KT SWLY LLJ...BUT IT IS
   MOVING SEWD FASTER THAN THE EWD RATE OF DESTABILIZATION. 
   MEANWHILE...CONVECTIVE OUTFLOW HAS REINFORCED THE SYNOPTIC WARM
   FRONT WHICH EXTENDS NWWD FROM NW IL ACROSS CENTRAL/NE IA TO SRN MN. 
   THE FRONT WILL MAKE SLOW NEWD PROGRESS TODAY AS THE MIDLEVEL TROUGH
   CONTINUES TO MOVE ESEWD TOWARD WI/NRN IL.  THE PRIMARY CONCERN THIS
   AFTERNOON WILL BE THE POTENTIAL FOR NEW CONVECTION TO DEVELOP ALONG
   THE FRONT/OUTFLOW...NEAR THE MIDLEVEL WAVE AXIS ACROSS NE IA AND WRN
   WI.
   
   A PLUME OF 8 C/KM MIDLEVEL LAPSE RATES FROM THE W...AND 70-72 F
   BOUNDARY LAYER DEWPOINTS FROM THE S/SW WILL COMBINE WITH DAYTIME
   HEATING TO SUPPORT A RESERVOIR OF 2500-3500 J/KG MLCAPE ALONG AND SW
   OF THE WARM FRONT/OUTFLOW.  THE MODERATE-STRONG INSTABILITY AND
   EFFECTIVE BULK SHEAR OF 45-55 KT BENEATH THE MIDLEVEL JET CORE WILL
   BE FAVORABLE FOR SUPERCELLS CAPABLE OF PRODUCING VERY LARGE HAIL AND
   DAMAGING WINDS.  THERE WILL ALSO BE A WINDOW OF OPPORTUNITY FOR A
   COUPLE OF TORNADOES ALONG THE BOUNDARY IN WI WITH THE MORE DISCRETE
   INITIAL STORMS...WHERE LOW-LEVEL SHEAR/MOISTURE WILL BE MAXIMIZED
   THIS AFTERNOON.  THIS EVENING INTO TONIGHT...CONVECTION WILL LIKELY
   EVOLVE INTO ANOTHER MCS AND SPREAD EWD/SEWD INTO LOWER MI/NW INDIANA
   IN ASSOCIATION WITH ASCENT DOWNSTREAM FROM THE MIDLEVEL WAVE. 
   
   FARTHER W/SW...WATER VAPOR IMAGERY SHOWS EVIDENCE OF AN UPSTREAM
   SPEED MAX OVER SD/NEB BORDER...WITH AN ASSOCIATED AREA OF MIDLEVEL
   CONVECTION.  AS THIS SPEED MAX AND ASCENT MOVE EWD/ESEWD TOWARD WRN
   IA THIS AFTERNOON...THERE WILL BE SOME POTENTIAL FOR THUNDERSTORM
   DEVELOPMENT.  HOWEVER...THE 12Z ABR/OAX SOUNDINGS SHOW A STRONG CAP
   SPREADING EWD WITH THE ELEVATED MIXED LAYER...AND RECENT VISIBLE
   SATELLITE IMAGERY/SURFACE OBSERVATIONS SUGGEST THAT THE OUTFLOW
   BOUNDARY ACROSS IA IS QUICKLY LOSING DEFINITION ACROSS CENTRAL IA
   AND MOVING NWD TOWARD MN.  GIVEN THESE UNCERTAINTIES...WILL ONLY
   INCLUDE 5% WIND/HAIL PROBABILITIES AS FAR W AS WRN IA.
   
   ..THOMPSON/ROGERS.. 08/23/2011
   
   CLICK TO GET WUUS01 PTSDY1 PRODUCT

   NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 2000Z