Thunderstorms formed in South Central North Dakota just north of the South Dakota border around 3 am on Monday, August 10, 2020. The storm line moved southeast across South Dakota, producing hail to 3″ in diameter and wind gusts as high as 73 mph.
The storms continued southeast into far northeast Nebraska, then turned due east (the path shaped like a hockey stick) and moved across Central Iowa (where the strongest winds occurred), Northern Illinois, far southern Wisconsin, then across Lake Michigan into SW Michigan and Indiana. The remnant line weakened as it moved across Michigan. After midnight, the storms had moved through much of W. Ohio and Kentucky. In the image above, note the bowing echo from 10 am to 5 pm (CDT), when the strongest winds occurred. In general, the strongest winds were along and just north of I-80 in IA and IL. From the Cedar Rapids Gazette (which has excellent coverage of the storm clean-up: