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 222000
   
   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0300 PM CDT SUN MAY 22 2011
   
   VALID 222000Z - 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 SWWD INTO
   THE SRN PLAINS...
   
   1630Z OUTLOOK ON TRACK WITH MINOR ADJUSTMENTS.
   
   THE FIRST ADJUSTMENT WAS TO EXTEND THE ERN END OF THE SLIGHT RISK
   EWD INTO NRN GA/WRN CAROLINAS/WRN VA AND WRN WV. STORMS THAT
   REDEVELOPED EAST OF MORNING MCS ACROSS THE TN VALLEY...NOW STRETCH
   FROM CENTRAL KY SWD INTO NRN AL. CURRENT ACTIVITY IS MOVING EWD AT
   30-40 KT AND NEW STORMS SHOULD CONTINUE TO DEVELOP AHEAD OF LINE IN
   UNCAPPED AND UNSTABLE AIR MASS. STORMS SHOULD WEAKEN AROUND SUNSET
   AS THEY MOVE INTO THE MOUNTAINS AND ENCOUNTER WEAKER INSTABILITY.
   
   SLIGHT RISK IN OK HAS BEEN SHIFTED EWD DUE TO THE CURRENT LOCATION
   OF DEVELOPING CU/DRYLINE. ALTHOUGH DRYLINE WILL RETREAT WWD THIS
   EVENING...LACK OF DYNAMICAL FORCING INDICATES THREAT FOR SEVERE
   STORMS REDEVELOPING WEST OF CURRENT STORMS APPEARS LOW. HOWEVER
   ...SLIGHT RISK REMAINS IN TACT BEHIND DRYLINE IN NRN OK/SRN KS WHERE
   STRONG/SEVERE STORMS ARE POSSIBLE TONIGHT IN ZONE OF STRONG LOW
   LEVEL WARM ADVECTION ASSOCIATED WITH LOW LEVEL JET. ALSO... SLIGHT
   RISK EXTENDED TO THE SWRN TX/MEXICO BORDER AS STORMS HAVE RECENTLY
   BEEN DEVELOPING SOUTH OF THE BORDER. ENVIRONMENT IS FAVORABLE FOR
   SUPERCELLS WITH VERY LARGE HAIL AND WIND DAMAGE. HAIL PROBABILITIES
   WERE INCREASED NEAR DRYLINE IN TX WHERE MORE NUMEROUS STORMS ARE
   LIKELY TO DEVELOP.
   
   MINOR ADJUSTMENTS TO MODERATE RISK AREA FROM WI SWD INTO MO TO
   ACCOUNT FOR RECENT TRENDS. KINEMATIC ENVIRONMENT IS VERY FAVORABLE
   FOR TORNADOES...SOME STRONG...ACROSS ERN MN/WI/ERN IA/ IL AND MO.
   MOST STORMS HAVE BEEN LOCATED WITHIN BANDS AND ARE FAVORABLE FOR
   HAIL..WIND DAMAGE AND TORNADOES.  TORNADOES ARE MORE LIKELY WITH
   DISCRETE STORMS. INTENSE SUPERCELLS HAD RECENTLY DEVELOPED IN ERN IA
   AND THESE TYPE OF STORMS ARE LIKELY INCREASE IN COVERAGE AND
   INTENSITY THROUGH THE AFTERNOON...WITH A GREATER POTENTIAL FOR
   STRONGER AND MORE SUSTAINED TORNADOES.
   
   ..IMY.. 05/22/2011
   
   .PREV DISCUSSION... /ISSUED 1117 AM CDT SUN MAY 22 2011/
   
   ...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.
   
   CLICK TO GET WUUS01 PTSDY1 PRODUCT

   NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 0100Z