There are already watches out, covering the entirety of Iowa, some of it in a “Particularly Dangerous Situation” designated tornado watch that butts into parts of Minnesota and Illinois. There are already strong storms appearing on the map, having initiated in eastern Nebraska, with the Omaha Metro seeing more tornado warnings earlier today. The storms will rage through Des Moines though the rush hour, and depart Cedar Rapids and the Twin Cities through about 7 or 8 PM. Cedar Rapids projects to get stronger storms, but Minneapolis and St. Paul will get a whole bunch of rain.

A concern I have is that the storms, already forming a bit of a wavy pattern in western Iowa, will transform into a derecho that continues through the night. If that’s the case, then an overnight squall in Chicago or Milwaukee would be possible. The SPC captured the concern with their enhanced risk extending through Lake Michigan. Be aware of the weather in the Upper Mississippi Valley tonight!