036 ACUS02 KWNS 011819 SWODY2 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 $$
