SPC AC 011817

   Day 2 Convective Outlook CORR 1
   NWS Storm Prediction Center Norman OK
   0117 PM CDT Mon Jun 01 2020

   Valid 021200Z - 031200Z

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FROM EXTREME
   EAST-CENTRAL SD INTO FAR NORTHERN IA...SOUTHERN MN AND CENTRAL WI...

   CORRECTED FOR THUNDER LINE IN THE NORTHEAST

   ...SUMMARY...
   Severe thunderstorms are expected Tuesday from the middle Missouri
   and upper Mississippi Valleys into the Great Lakes. Damaging wind
   gusts, large hail and a couple of tornado are possible, with the
   greatest threat expected from southern Minnesota into central
   Wisconsin.

   ...Synopsis...

   An active day is expected on Tuesday as several northern-stream
   shortwave troughs/impulses migrate from the northern Plains to the
   lower Great Lakes atop a southern stream upper ridge centered over
   the southern/central High Plains. 

   ...SD/NE into Lower MI...

   Rich boundary layer moisture will continue to stream into the mid-MO
   Valley and Great Lakes vicinity on strong southerly low level winds.
   Surface dewpoints are forecast to range from the mid/upper 60s to
   perhaps near 70 F along and ahead of a cold front from western upper
   MI into central MN and southeast SD midday Tuesday. Strong heating
   is forecast across the region, with high temperatures generally in
   the upper 80s to low 90s. A plume of steep midlevel lapse rates (7-8
   C/km) will overspread the region, supporting MLCAPE values from
   2000-4000 J/kg. Meanwhile, a band of 35-45 kt bulk effective shear
   will support organized convection. 

   Supercells may initially develop near a triple point over southeast
   SD east/northeast along the surface boundary across southern MN.
   Thermodynamic and shear parameters will support storms initially
   capable of very large hail (some potentially bigger than 2 inches in
   diameter), and damaging gusts. Where low level SRH is enhanced near
   the surface low and along the surface boundary, a couple of
   tornadoes could occur with any discrete convection. Convection is
   expected to grow upscale within a few hours of initiation as frontal
   forcing increases, and as thunderstorm outflows/cold pool production
   becomes more supportive of bowing segments across parts of northern
   IA, far southern MN and into WI/MI during the evening and overnight
   hours.

   ...WY into the central Plains...

   A dryline will extend southwestward from the surface low over
   southeast SD through central NE and into northwest KS. Isolated
   supercells are expected to develop during the afternoon in this very
   unstable but weaker shear environment. a deeply-mixed boundary layer
   and steep low level lapse rates will favor strong, locally damaging
   gusts and possibly some large hail. Further west, thunderstorms are
   expected to develop over higher terrain in WY. As these higher-based
   storms move eastward off of the higher terrain, a few intense cells
   could support locally strong gusts and hail through the evening
   hours. 

   ...Lower Great Lakes Vicinity...

   Morning showers and cloud cover are expected across parts of
   northeast OH into western NY/PA on the back side of an exiting
   shortwave impulse.  This cloud cover should clear the area by
   afternoon, as rich moisture advects northeastward across the region.
   Convection is expected to develop across Ontario along the eastern
   extension of the surface cold front and spread south/southeast into
   northeast OH and western PA/NY during the evening and overnight
   hours. Strong wind gusts and small hail are the main threats
   expected with this activity.

   ..Leitman.. 06/01/2020

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