A multiday siege of severe weather will first strike the Great Lakes and Midwest through the end of this week before shifting to the Great Plains over the weekend and into early next week.Tornadoes – some possibly strong – damaging hail and destructive straight-line winds are all potential threats.

Cities such as Chicago, Minneapolis and Milwaukee are at risk for a severe weather outbreak, forecasters said.

Tens of millions of people from the Upper Midwest to the Ohio Valley are on alert as a multiday severe weather threat begins Wednesday, with forecasters warning of storms capable of producing tornadoes,