 And that's where they really exploded in the heat of the day, congealed into a big complex of thunderstorms, what we call an MCS, a mesoscale convective system. Fancy name for a huge blob of thunderstorms that can pick up steam and tap into the jet stream, literally, because those storms get so high, up 50,000, 60,000 feet, the jet stream can start to push them along rapidly. And they produce damaging winds from Iowa all the way into the Chicago area, 97 mile an hour wind reported in Iowa.