Radar image of the storms heading for the Chicago area at 6:05 pm ET.
A nasty line of storms has barreled across Iowa today, taking aim at Milwaukee and Madison, Wisconsin, as well as Chicago and Rockford, Illinois, during the next few hours.
The storm complex is technically known as a mesoscale convective system, basically a large group of organized thunderstorms. These storms are feeding off a warm, moist air mass, and strong winds in the low and mid-levels of the atmosphere are being pulled down to the surface, making them especially dangerous.
The National Weather Service issued a rare "Particularly Dangerous Situation" severe thunderstorm watch" for areas from Chicago to South Bend, Indiana, as the storms plow eastbound. Wind gusts to 80 miles per hour or greater are possible with these storms.