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 221617
   
   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   1117 AM CDT SUN MAY 22 2011
   
   VALID 221630Z - 231200Z
   
   ...THERE IS A MDT RISK OF SVR TSTMS OVER SERN MN...ERN IA...PARTS OF
   WI/IL/MO...NERN OK AND NWRN AR...
   
   ...THERE IS A SLGT RISK OF SVR TSTMS FROM THE GREAT LAKES INTO THE
   SRN PLAINS...
   
   ...UPPER GREAT LAKES INTO THE MID MS AND OH VALLEYS...
   
   DEEP-LAYER CYCLONE OVER ERN SD WILL TRANSLATE EWD INTO THE UPPER MS
   VALLEY BY THIS EVENING WITH AN ASSOCIATED 50-60 KT MIDLEVEL JET
   STREAK OVERSPREADING THE UPPER MIDWEST THROUGH THE PEAK OF THE
   DIURNAL HEATING CYCLE.  SURFACE CYCLONE WILL ACCORDINGLY DEVELOP EWD
   TO CNTRL MN BY 23/00Z WITH ASSOCIATED WARM FRONT RAPIDLY LIFTING NWD
   THROUGH ERN IA/IL INTO WI AND LOWER MI TODAY.  HEIGHT FALLS/DYNAMIC
   FORCING FOR ASCENT ATTENDANT TO MIDLEVEL SYSTEM COUPLED WITH FRONTAL
   UPLIFT WILL FOSTER SCATTERED SVR TSTMS BY EARLY AFTERNOON INITIALLY
   FROM PORTIONS OF E-CNTRL/SERN MN AND ERN IA/NERN MO INTO WI/IL.
   
   THE COMBINATION OF A MOIST...MODERATELY TO STRONGLY UNSTABLE AIR
   MASS --I.E. MLCAPE RANGING FROM 1000-1500 J/KG OVER MN/WI TO
   2000-3000 J/KG ACROSS MO/IL-- COUPLED WITH 40-50 KT DEEP-LAYER SHEAR
   ORIENTED ORTHOGONAL TO SURFACE FRONT WILL YIELD A BAND OF SUPERCELLS
   CAPABLE OF TORNADOES...LARGE HAIL AND DAMAGING WINDS.  THE GREATEST
   TORNADO POTENTIAL --SOME POTENTIALLY SIGNIFICANT-- APPEARS TO BE
   ACROSS CNTRL/SRN WI INTO IL THIS AFTERNOON AND EVENING WHERE
   LOW-LEVEL SHEAR WILL BE ENHANCED BY A GRADUALLY STRENGTHENING LLJ.
   
   STORMS MAY GROW UPSCALE INTO A QLCS TONIGHT WITH A CONTINUED THREAT
   FOR MAINLY HAIL AND DAMAGING WIND GUSTS SPREADING EWD THROUGH LOWER
   MI AND THE OH VALLEY.
   
   FOR ADDITIONAL NEAR TERM GUIDANCE...SEE MCD 849.
   
   ...SRN PLAINS...
   
   12Z REGIONAL SOUNDINGS SHOWED THE POTENTIAL FOR EXPLOSIVE TSTM
   DEVELOPMENT LATER TODAY WITH A VERY MOIST BOUNDARY LAYER BENEATH
   STEEP MIDLEVEL LAPSE RATES...RESULTING IN MLCAPE OF 3000-4000 J/KG. 
   GIVEN THAT LARGE-SCALE FORCING FOR ASCENT WILL REMAIN NEGLIGIBLE
   THROUGH THE DIURNAL HEATING CYCLE...THE PRIMARY UNCERTAINTIES ARE
   LOCATION AND EVENTUAL COVERAGE OF SEVERE STORMS.
   
   DRYLINE LOCATED FROM WRN OK INTO W-CNTRL AND SWRN TX AS OF MID
   MORNING WILL MIX MOST RAPIDLY EWD TODAY ACROSS NRN HALF OF OK WITH
   THE BOUNDARY EXTENDING FROM E OF THE I-44 CORRIDOR INTO W-CNTRL TX
   BY MID/LATE AFTERNOON.  CURRENTLY THE HIGHEST PROBABILITY FOR
   DIURNAL TSTM DEVELOPMENT APPEARS TO BE FROM NERN OK NEWD INTO MO
   WHERE AREA WILL BE INFLUENCED BY LEFT EXIT REGION OF UPPER JET
   STREAK STRETCHING FROM THE SRN ROCKIES INTO SRN PLAINS. 
   HOWEVER...GIVEN THE POTENTIAL FOR STRONG HEATING W OF DRYLINE AND A
   BREAKABLE CAP /SEE 12Z FWD SOUNDING/...ISOLATED SEVERE STORMS WILL
   BE POSSIBLE ALONG THE LENGTH OF THE DRYLINE.
   
   LATEST MODEL GUIDANCE SUGGESTS DEEPER PBL MIXING MAY LEAD TO
   DECREASING LOW-LEVEL MOISTURE CONTENT THIS AFTERNOON...LARGELY
   ACROSS PORTIONS OF CNTRL/ERN TX.  WHILE THIS MAY TEMPER THE DEGREE
   OF INSTABILITY...EXPECT AFTERNOON MLCAPE VALUES OF 3000-4000+ J/KG. 
   WHEN COUPLED WITH 35-40 KT OF DEEP WLY SHEAR...SETUP WILL FAVOR THE
   DEVELOPMENT OF SUPERCELLS WITH VERY LARGE HAIL BEING THE PRIMARY
   HAZARD.  THE TORNADO THREAT WILL INCREASE IN THE 23/00-03Z TIME
   PERIOD AS A STRENGTHENING SLY LLJ ENHANCES LOW-LEVEL SHEAR.
   
   ...LOWER MS/TN VALLEYS INTO SRN APPALACHIANS...
   
   REGENERATIVE TSTM DEVELOPMENT IS OCCURRING THIS MORNING ACROSS AR
   WITHIN A ZONE OF LOW-LEVEL WAA ASSOCIATED WITH A SWLY LLJ
   ORIGINATING OVER SRN TX.  CONTINUED HEATING/DESTABILIZATION ALONG
   THE SRN/ERN PERIPHERY OF ONGOING STORMS IN CONCERT WITH A
   GROWING/DEEPENING COLD POOL MAY ALLOW FOR THE DEVELOPMENT OF A
   FORWARD-PROPAGATING MCS WITH EMBEDDED SUPERCELLS WHICH WOULD TRACK
   ACROSS THE TN VALLEY AND NRN GULF COAST STATES WITH ATTENDANT
   THREATS OF DAMAGING WINDS AND HAIL AND PERHAPS A COUPLE TORNADOES.
   
   FOR ADDITIONAL NEAR-TERM GUIDANCE...SEE MCD 850.
   
   ...LOWER GREAT LAKES INTO NC...
   
   THE EWD PROGRESSION OF A COUPLE OF WEAK MIDLEVEL IMPULSES WILL
   PROVIDE SUFFICIENT BACKGROUND FORCING TO SUPPORT DIURNAL TSTM
   DEVELOPMENT WITHIN A WARMING/DESTABILIZING AIR MASS WHERE AFTERNOON
   MLCAPE WILL RANGE FROM 1000-2000 J/KG OVER NC TO AROUND 500 J/KG
   ACROSS PORTIONS OF NY/PA.  THE STRONGEST VERTICAL SHEAR WILL RESIDE
   ACROSS THE LOWER GREAT LAKES...DIMINISHING WITH SWD EXTENT.  AS
   SUCH...THE POTENTIAL WILL EXIST FOR A FEW STRONG-MARGINALLY SEVERE
   STORMS THIS AFTERNOON INTO EVENING WITH THE PRIMARY THREATS BEING
   HAIL AND LOCALLY STRONG WIND GUSTS.
   
   ..MEAD/GRAMS.. 05/22/2011
   
   CLICK TO GET WUUS01 PTSDY1 PRODUCT

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