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 011250
   
   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0750 AM CDT THU SEP 01 2011
   
   VALID 011300Z - 021200Z
   
   ...THERE IS A SLGT RISK OF SVR TSTMS FROM MN INTO NWRN WI AND WRN
   LAKE SUPERIOR...
   
   ...MN INTO NWRN WI AND WRN LAKE SUPERIOR...
   ONGOING MCS OVER NRN MN IS EXPECTED TO CONTINUE WEAKENING THIS
   MORNING AS IT MOVES PROGRESSIVELY EAST OF THE LOW LEVEL JET AND INTO
   A MARGINALLY UNSTABLE ENVIRONMENT.
   
   POSITIVELY TILTED UPPER TROUGH OVER THE NWRN STATES IS FORECAST TO
   MOVE EWD ACROSS MT AND ND AS AN UPSTREAM TROUGH DIGS SEWD FROM THE
   GULF OF AK...RESULTING IN A BROAD LONG WAVE TROUGH OVER THE NWRN/N
   CNTRL STATES.  SATELLITE IMAGERY INDICATES A WEAK SHORT WAVE TROUGH
   OVER THE WRN DAKOTAS THAT WILL MOVE NEWD TOWARD THE UPPER MS VALLEY
   BY THIS EVENING.  SURFACE LOW OVER NERN SD IS EXPECTED TO MOVE EWD
   INTO MN TODAY CONTINUING INTO WRN LAKE SUPERIOR TONIGHT.  A COLD
   FRONT WILL MOVE EWD FROM THE DAKOTAS AND EXTEND FROM NRN MN INTO
   SERN SD AND NWRN NEB BY THIS EVENING...REACHING A WRN UPPER
   MI/CENTRAL IA/WRN KS LINE BY THE END OF THE PERIOD.  SOUTHERLY LOW
   LEVEL WINDS AHEAD OF THE COLD FRONT WILL TRANSPORT HIGHER SURFACE
   DEW POINTS NWD INTO THE UPPER MS VALLEY.
   
   STEEP MID LEVEL LAPSE RATES AND AN ASSOCIATED CAPPING INVERSION IS
   FORECAST TO SPREAD EWD ACROSS THE UPPER MS VALLEY AND INHIBIT
   DEVELOPMENT OF SURFACE-BASED CONVECTION ALONG/AHEAD OF THE COLD
   FRONT INTO THE AFTERNOON.  MESOSCALE AND CONVECTION-ALLOWING MODEL
   GUIDANCE INDICATES STORMS ARE MOST LIKELY TO DEVELOP OVER
   NRN/CENTRAL MN LATE THIS AFTERNOON AND EVENING WITHIN A STRONGLY
   UNSTABLE AIR MASS /MLCAPE OF 2500-3500 J PER KG/...IN RESPONSE TO
   STRONG DIABATIC HEATING COUPLED WITH ASCENT IN ADVANCE OF THE
   AFOREMENTIONED SHORT WAVE TROUGH MOVING TOWARD THE UPPER MS VALLEY. 
   DEEP LAYER SHEAR OF 35-45 KT IN THE LOWEST 6 KM WILL ENHANCE STORM
   ORGANIZATION AND INTENSITY WITH POTENTIAL FOR A FEW SUPERCELLS TO
   DEVELOP INITIALLY.  THESE WILL BE CAPABLE OF PRODUCING LARGE
   HAIL...DAMAGING WIND GUSTS...AND POSSIBLY SEVERAL TORNADOES.  THIS
   ACTIVITY IS EXPECTED TO GROW UPSCALE INTO A SMALL MCS LATER THIS
   EVENING AND MOVE EWD INTO PARTS OF NWRN WI AND LAKE SUPERIOR DURING
   THE OVERNIGHT HOURS...WITH THE PRIMARY THREAT TRANSITIONING TO
   DAMAGING WIND GUSTS AND HAIL.
   
   ...CENTRAL PLAINS...
   CONVECTIVE DEVELOPMENT FARTHER SWWD ALONG THE COLD FRONT FROM SWRN
   MN INTO THE CENTRAL PLAINS WILL BE LIMITED BY THE EML/CAPPING
   INVERSION...ESPECIALLY DURING THE DAYTIME HOURS.  POTENTIAL FOR
   ISOLATED THUNDERSTORMS IS EXPECTED TO INCREASE BY LATE AFTERNOON OR
   EVENING INTO PARTS OF SD/NEB...AND IN THE POST-FRONTAL UPSLOPE FLOW
   REGIME INTO NERN WY.  STEEP LAPSE RATES WILL ENHANCE THREAT FOR HAIL
   AND POSSIBLY STRONG WIND GUSTS WITH STRONGER CELLS THAT CAN
   DEVELOP...BUT LIMITED STORM COVERAGE PRECLUDES HIGHER SEVERE
   PROBABILITIES AT THIS TIME.
   
   ...OH VALLEY INTO PA...
   WIDESPREAD THUNDERSTORMS HAVE BEEN MOVING SEWD ACROSS PARTS OF LAKE
   ERIE/ERN OH/SWRN NY/AND WRN PA THIS MORNING IN ADVANCE OF A SHORT
   WAVE TROUGH MOVING SEWD TOWARD THE LOWER GREAT LAKES.  A
   DIFFERENTIAL HEATING BOUNDARY MAY BECOME ESTABLISHED ALONG THE
   COMPOSITE WRN EDGE OF THE MORE DENSE CLOUDS/PRECIPITATION OVER
   EXTREME ERN OH/WRN PA...POSSIBLY PROVIDING A FOCUS FOR NEW
   THUNDERSTORM DEVELOPMENT THIS AFTERNOON.  HOWEVER...ADDITIONAL
   CONVECTION HAS BEEN DEVELOPING OVER EXTREME ERN INDIANA/WRN OH
   WITHIN A REGION OF LOW LEVEL WARM ADVECTION...AND IT IS UNCLEAR WHAT
   IMPACT IF ANY THIS MAY HAVE ON LOW LEVEL BOUNDARIES LATER TODAY. 
   NWLY FLOW ALOFT IS FORECAST TO INCREASE IN MAGNITUDE THIS AFTERNOON
   AND PROVIDE SUFFICIENT DEEP LAYER SHEAR FOR ORGANIZED MULTICELL AND
   POSSIBLY ISOLATED SUPERCELL STORMS.  THERE IS POTENTIAL FOR
   REDEVELOPMENT OF A FEW STRONG/SEVERE THUNDERSTORMS INTO THE
   AFTERNOON GIVEN FAVORABLE SHEAR PROFILES...BUT UNCERTAINTY IN THE
   MESOSCALE ENVIRONMENT EVOLUTION PRECLUDES INCREASING THE LOW SEVERE
   PROBABILITIES AT THIS TIME.
   
   ...SRN LA COASTAL AREA...
   SATELLITE IMAGERY INDICATES AN INCREASING AREA OF CONVECTION OVER
   THE NORTH CENTRAL GULF OF MEXICO WHICH IS ASSOCIATED WITH A LOW
   PRESSURE SYSTEM IN THE CENTRAL GULF.  CONSENSUS OF MODEL GUIDANCE
   INDICATES THE LOW WILL MOVE NWD TONIGHT SOUTH OF LA...WITH
   INCREASING SELY/ELY LOW LEVEL WINDS SPREADING OVER SRN LA.  THIS
   WILL RESULT IN STRENGTHENING LOW LEVEL SHEAR...AND MOST CONVECTION
   ALLOWING MODELS PREDICT DEVELOPMENT OF A FEW SUPERCELLS MOVING WWD
   ACROSS PARTS OF SRN LA...ESPECIALLY TONIGHT.  THUS...LOW TORNADO AND
   SEVERE WIND PROBABILITIES HAVE BEEN INTRODUCED INTO PARTS OF SRN LA.
   
   ..WEISS/SMITH.. 09/01/2011
   
   CLICK TO GET WUUS01 PTSDY1 PRODUCT

   NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1630Z