SPC AC 180109

   Day 1 Convective Outlook CORR 1
   NWS Storm Prediction Center Norman OK
   0809 PM CDT Fri Jul 17 2020

   Valid 180100Z - 181200Z

   ...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS OVER SOUTHEAST
   NORTH DAKOTA...EXTREME NORTHEAST SOUTH DAKOTA,CENTRAL AND NORTHERN
   MINNESOTA AND NORTHWEST WISCONSIN...

   CORRECTED FOR TEXT IN 3RD PARAGRAPH

   ...SUMMARY...
   A significant severe weather event will continue this evening and
   overnight over parts of North Dakota, northeast South Dakota,
   northern and central Minnesota, and western Wisconsin. Widespread
   damaging wind is the primary threat, though large hail and a few
   tornadoes will also remain possible.

   ...Northern Plains across upper Midwest/western Great Lakes...

   Higher severe probabilities were shifted southward across MN to
   account for the slightly more southern anticipated motion of the
   severe MCS tonight, and removed in the wake of the convective system
   where a substantial cold pool has stabilized the atmosphere.

   A well-developed MCS continues to move east-southeast across
   central/eastern ND and northwest MN at 01z. Evening mesoanalysis
   placed a warm front across northern sections of MN/WI with a cold
   front extending southward across western ND. Along and south of the
   warm front and east of the cold front, 00z soundings and objective
   analysis shows strong to extreme surface-based instability beneath a
   plume of very steep mid-level lapse rates, with moderate westerly
   flow contributing to 35-40 kts of effective shear. 

   Current expectations are for additional thunderstorms to continue
   developing ahead of the cold front this evening with the evolving
   line surging towards the Tri-State region this evening. Aided by
   developing warm advection with a nocturnally-strengthening low level
   jet developing across southern/central MN, a severe MCS/derecho is
   expected to move rapidly east across central/northern MN, northwest
   WI and possibly the western upper peninsula of MI overnight. The
   relatively pristine downstream environment characterized by a lack
   of significant pre-MCS convection suggests a significant damaging
   wind event will continue well into the overnight hours.  

   Elsewhere, removed severe probabilities across the mid-Atlantic
   region and MT.

   ..Bunting.. 07/18/2020

   CLICK TO GET WUUS01 PTSDY1 PRODUCT

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