Jul 18, 2011 0100 UTC Day 1 Convective Outlook
Updated: Mon Jul 18 01:02:07 UTC 2011
Probabilistic to Categorical Outlook Conversion Table
Public Severe Weather Outlook

The SPC is forecasting ...severe thunderstorms expected over parts of the northern plains this afternoon....   Please read the latest public statement about this event.

Categorical Graphic
20110718 0100 UTC Day 1 Outlook Graphic
Probabilistic Tornado Graphic
20110718 0100 UTC Day 1 Tornado Probabilities 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
20110718 0100 UTC Day 1 Damaging Wind Probabilities 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
20110718 0100 UTC Day 1 Large Hail Probabilities 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 180057
   
   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0757 PM CDT SUN JUL 17 2011
   
   VALID 180100Z - 181200Z
   
   ...THERE IS A SLGT RISK OF SVR TSTMS FROM THE UPPER MIDWEST TO UPPER
   GREAT LAKES...
   
   ...THERE IS A SLGT RISK OF SVR TSTMS ACROSS NRN NY AND NRN NEW
   ENGLAND...
   
   ...ERN ND/NERN SD...UPPER MS VALLEY TO UPPER GREAT LAKES...
   WATER VAPOR IMAGERY SHOWED AN APPARENT SHORTWAVE TROUGH TRACKING
   ESEWD INTO NWRN WI...WITH A 50 KT WLY MIDLEVEL JET EXTENDING FROM ND
   INTO NRN ONTARIO/LAKE SUPERIOR ATTENDANT TO A SECOND MIDLEVEL SYSTEM
   MOVING THROUGH NRN ONTARIO.
   
   LATE AFTERNOON/EARLY EVENING SURFACE ANALYSES SHOWED AN AREA OF
   LOWER PRESSURE LOCATED OVER CENTRAL SD WITH A FRONT EXTENDING EWD
   THROUGH CENTRAL MN...NRN WI..FAR NRN LOWER MI...TO CENTRAL ONTARIO. 
   RICH MOISTURE RESIDES ALONG AND S OF THIS BOUNDARY FROM THE ERN
   DAKOTAS TO WI WITH SURFACE DEWPOINTS IN THE MID 70S TO AROUND 80 F. 
   THIS MOISTURE COUPLED WITH A PLUME OF STEEP MIDLEVEL LAPSE RATES
   /7.5-8 C PER KM/ EXTENDING FROM SD TO WI WILL MAINTAIN A RESERVOIR
   OF MODERATE TO VERY STRONG INSTABILITY THROUGH THIS FORECAST PERIOD.
    A STRENGTHENING SWLY LLJ INTO ERN SD/SRN MN THIS EVENING/TONIGHT
   WITHIN THE ENTRANCE REGION OF THE AFOREMENTIONED WLY MIDLEVEL JET
   WILL RESULT IN A WAA REGIME INVOF THE W-E ORIENTED SURFACE FRONT. 
   VERY STRONG INSTABILITY AND EFFECTIVE BULK SHEAR AROUND 50 KT WILL
   MAINTAIN A THREAT FOR AN ISOLATED TORNADO AND VERY LARGE HAIL YET
   THIS EVENING ACROSS SERN ND INTO ADJACENT WEST CENTRAL MN. 
   OTHERWISE...AN INCREASE IN ADDITIONAL CONVECTION ACROSS CENTRAL/SRN
   MN TONIGHT COULD POSE A THREAT FOR SEVERE STORMS WITH HAIL AND
   STRONG WIND GUSTS THE PRIMARY THREATS AS ACTIVITY SPREADS ESEWD.
   
   FARTHER E...UPSCALE GROWTH IS EXPECTED TO CONTINUE ACROSS NRN WI
   ALONG THE NRN PERIPHERY OF A RESERVOIR OF VERY STRONG INSTABILITY
   EXTENDING FROM CENTRAL/SRN MN INTO MUCH OF WI.  A STRENGTHENING
   WSWLY LLJ INTO WI TONIGHT WILL SUPPORT FORWARD PROPAGATION OF THIS
   SYSTEM ACROSS NRN WI INTO LOWER MI...WITH DAMAGING WINDS AND HAIL
   THE PRIMARY THREATS.  ADDITIONAL STRONG TO SEVERE STORMS THAT
   DEVELOP LATER TONIGHT ACROSS MN...MAY REACH WEST CENTRAL/SWRN WI
   LATE IN THE PERIOD...MAINTAINING THE SLIGHT RISK ACROSS THOSE AREAS.
   
   
   ...NRN NY TO NRN NEW ENGLAND...
   THE ERN EXTENT OF A STEEP MIDLEVEL LAPSE RATE PLUME WILL AID IN
   MAINTAINING AT LEAST MARGINAL INSTABILITY AFTER DARK ACROSS NRN NY
   TO NRN NEW ENGLAND.  AN ONGOING FORWARD PROPAGATING MCS...CURRENTLY
   MOVING ESEWD ACROSS FAR SRN QUEBEC INTO FAR NRN NY...IS EXPECTED TO
   PROGRESS INTO THE REST OF THIS DISCUSSION AREA WITH DAMAGING WIND
   AND HAIL THE PRIMARY THREATS.  MODELS SUGGEST ADDITIONAL STORMS MAY
   REACH NRN NY TOWARD 12Z AS AN UPSTREAM COLD FRONT APPROACHES THIS
   REGION.
   
   ..PETERS.. 07/18/2011
   
   CLICK TO GET WUUS01 PTSDY1 PRODUCT

   NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 0600Z