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 221255
   
   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0755 AM CDT SUN MAY 22 2011
   
   VALID 221300Z - 231200Z
   
   ...THERE IS A MDT RISK OF SVR TSTMS FROM PARTS OF SRN PLNS NORTH AND
   EAST INTO THE MID AND UPR MS VLYS...
   
   ...THERE IS A SLGT RISK OF SVR TSTMS SURROUNDING THE MDT RISK
   AREA...FROM S TX NORTHEAST TO THE UPR GRT LKS...
   
   ...SYNOPSIS...
   SD CLOSED LOW EXPECTED TO TRACK ENE TO SRN MN THIS EVE AND EVOLVE
   INTO AN OPEN WAVE OVER WI EARLY MON AS BROAD...NEGATIVE TILT 
   UPSTREAM TROUGH AMPLIFIES SE ACROSS THE WRN U.S.  BETWEEN THESE TWO
   FEATURES...A WEAK SHORTWAVE RIDGE WILL SHIFT E FROM THE CNTRL/SRN
   RCKYS TO THE CNTRL/SRN PLNS.  AT THE SFC...A COLD/OCCLUDED FRONT
   WILL MOVE E ACROSS THE MID/UPR MS VLY AND ACROSS ERN KS/MO LATER
   TODAY/TONIGHT...WHILE FARTHER S...DRYLINE WILL PERSIST FROM SE KS TO
   THE TX BIG BEND.  THE DRYLINE WILL INTERSECT THE COLD FRONT IN KS
   AND WILL RETREAT NW ACROSS THE SRN PLNS LATER IN THE PERIOD.
   
   BOTH THE COLD FRONT AND THE DRYLINE WILL SERVE TO FOCUS INTENSE TSTM
   DEVELOPMENT LATER TODAY INTO TONIGHT.  GIVEN THE DEGREE OF BOTH
   INSTABILITY AND SHEAR PRESENT NEAR THE BOUNDARIES...SOME OF THE
   STORMS LIKELY WILL YIELD VERY LARGE HAIL...TORNADOES...AND DMGG
   WIND.
   
   ...MID/UPR MS VLY TO GRT LKS/OH VLY...
   STRENGTHENING SSWLY LLJ AHEAD OF UPR VORT MAX IN BASE OF SD UPR LOW
   SHOULD ALLOW FOR SUBSTANTIAL AIR MAS RECOVERY NWD ACROSS MUCH OF
   IA...SE MN...NRN MO...IL...AND WI THIS MORNING...IN WAKE OF
   OVERNIGHT SQLN.  WITH TIME...LOW LVL MOISTURE SHOULD ALSO SPREAD
   NEWD FROM THE MID MS VLY INTO THE GRT LKS/OH VLY.  COUPLED WITH
   MODERATE SFC HEATING AND RELATIVELY COOL MID LVL TEMPS...EXPECT
   2000-3000 J/KG SBCAPE BY AFTN WHERE STRONGEST HEATING OCCURS.
   
   COMBINATION OF STRONG DESTABILIZATION WITH CONVERGENCE ALONG/AHEAD
   OF AFOREMENTIONED COLD/OCCLUDED FRONT...AND INCREASING UVV SHOULD
   SUPPORT SEVERAL BROKEN BANDS OF STORMS OVER PARTS OF IA...SE
   MN...AND WRN WI BY MIDDAY.  ADDITIONAL STORMS SHOULD DEVELOP SWD AND
   EWD INTO PARTS OF MO AND WRN/NRN IL BY MID TO LATE AFTN AS BAND OF
   50 KT 700 MB FLOW OVERSPREADS REGION ON S SIDE OF UPR VORT.
   
   GIVEN STRENGTH OF WIND FIELD AND DEGREE OF INSTABILITY...POTENTIAL
   WILL EXIST FOR NUMEROUS SUPERCELL STORMS.  WHILE DESTRUCTIVE
   INTERFERENCE ULTIMATELY MAY LIMIT STORM LONGEVITY...A WINDOW OF
   OPPORTUNITY WILL EXIST FOR A FEW SUSTAINED SUPERCELLS POSING A
   THREAT FOR STRONG TORNADOES IN ADDITION TO LARGE HAIL/LOCALLY DMGG
   WIND....ESPECIALLY FROM WRN WI SWD THROUGH SE MN INTO ERN IA...WRN
   IL...AND POSSIBLY NE MO.  WITH TIME...STRENGTH OF FORCING AND
   CONTINUED ENE MOTION OF UPR VORT SUGGEST THAT THE ACTIVITY WILL
   EVOLVE INTO A BROKEN QLCS...WITH A THREAT FOR DMGG WIND...SVR HAIL
   AND ISOLD TORNADOES CONTINUING EWD TO THE CHICAGO AREA AND POSSIBLY
   INTO PARTS OF LWR MI/IND TONIGHT.
   
   ...SRN PLNS...
   VERY RICH GULF MOISTURE...WITH LOW 70S F SFC DEWPOINTS AND PW AROUND
   1.75 INCHES...WILL PERSIST/SPREAD NWD ACROSS THE SRN HALF OF THE
   PLNS TODAY BENEATH BROAD STEEP MID LVL LAPSE RATE PLUME ASSOCIATED
   WITH SRN STREAM WSWLY FLOW/EML.  COUPLED WITH STRONG SFC
   HEATING...SETUP LIKELY WILL YIELD A CORRIDOR OF VERY STRONG
   INSTABILITY /SBCAPE UP TO 6000 J PER KG/ ALONG AND AHEAD OF DRY
   LINE/COLD FRONT FROM S CNTRL TX NEWD INTO SE KS...SW MO...AND NW AR
   BY LATE TODAY.
   
   LARGE SCALE FORCING FOR ASCENT WILL BE WEAK THROUGH THE
   PERIOD...WITH SLIGHT HEIGHT RISES POSSIBLE AS LOW AMPLITUDE RIDGE
   APPROACHES REGION.  IN ADDITION...APPRECIABLE CINH WILL BE PRESENT
   DUE TO EML.  BUT COMBINATION OF STRONG INSTABILITY WITH SLIGHTLY
   CONFLUENT LOW LVL SSWLY FLOW SHOULD SUPPORT AT LEAST WDLY SCTD
   INTENSE STORMS FROM ERN OK INTO SW MO/NW AR BY LATE IN THE DAY. 
   MORE ISOLD INTENSE ACTIVITY ALSO MAY OCCUR FROM CNTRL OK SWD INTO S
   CNTRL TX.
   
   GIVEN DEGREE OF INSTABILITY AND AMPLE DEEP SHEAR FOR 
   SUPERCELLS...POTENTIAL WILL BE VERY HIGH FOR AT LEAST A FEW
   INSTANCES OF EXTREMELY LARGE HAIL...IN ADDITION TO TORNADOES/LOCALLY
   DMGG WIND.  STRENGTHENING LLJ AFTER NIGHTFALL AND CONTINUING
   PRESENCE OF VERY RICH MOISTURE SUGGEST THAT THE TORNADO THREAT COULD
   CONTINUE WELL INTO THE EVENING.
   
   ADDITIONAL STORMS MAY FORM OVER PARTS OF CNTRL AND NW TX AND
   CNTRL/WRN OK LATE TONIGHT AND EARLY MONDAY AS LLJ CONTINUES TO
   STRENGTHEN AND SLIGHTLY BACKS AHEAD OF AMPLIFYING SRN STREAM
   TROUGH...ENHANCING WAA/MOISTURE FLUX INVOF RETREATING DRY LINE.
   
   ...LWR TN/LWR OH VLYS...
   TSTM COMPLEX NOW OVER AR MAY PERSIST THROUGH MIDDAY AND BE
   ACCOMPANIED BY ADDITIONAL DEVELOPMENT NEWD INTO THE TN/LWR OH VLYS
   AS AREA OF LOW LVL MOISTURE RETURN DESTABILIZES BENEATH SRN FRINGE
   OF CYCLONIC MID/UPR LVL FLOW.  SUFFICIENT INSTABILITY AND SHEAR WILL
   BE PRESENT TO SUPPORT SOME SUSTAINED ACTIVITY AND POSSIBLY
   ORGANIZATION INTO ONE OR TWO NEW CLUSTERS POSING A THREAT FOR DMGG
   WIND/HAIL AND...ASSUMING FAVORABLE STORM MODE... POSSIBLY A COUPLE
   TORNADOES THROUGH AT LEAST EARLY TONIGHT.
   
   ..CORFIDI/SMITH.. 05/22/2011
   
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