Hot, humid air surging into the Upper Midwest will help ignite potentially damaging thunderstorms into tonight.
This afternoon started with plenty of blazing sunshine across the Upper Midwest. However, clouds and severe thunderstorms will become more numerous into the evening.
A low pressure system shifting eastward across the northern Plains will be the trigger for the thunderstorms, while the hot, muggy air will act as the fuel.
The severe weather will first develop across northern Minnesota, then shift eastward to other places in the vicinity of Lake Superior tonight.
Another area of violent thunderstorms will erupt along the system's cold front from northern Wisconsin to Iowa tonight. This zone stretches across Waterloo, Iowa.
Damaging wind gusts over 60 mph and large hail will be concerns with the strongest thunderstorms.
Winds will be capable of knocking down trees and power lines, potentially causing damage to homes and vehicles and cutting power to some areas. The largest hail, up to the size of golf balls, could dent cars and break windows.
A few of the strongest thunderstorms could spawn tornadoes.
The stage is set for isolated tornadoes due to the fact that there will be weaker southerly winds at the surface and strong west-southwest winds high in the atmosphere.
On Wednesday, the severe weather threat zone will target more of the Great Lakes and St. Lawrence Valley.
Severe thunderstorms could also initially ignite westward to the North Dakota border.
Severe Weather Threat Also across the South
Hot, muggy weather and daytime heating will allow additional severe thunderstorms to erupt across the Gulf Coast into this evening.
The spine of the Appalachians will also remain at risk for severe weather into this evening as a cluster of intense thunderstorms drops southward.
These thunderstorms, which originated from southern Ontario earlier today, have already left a trail of wind damage from eastern Ohio to West Virginia.