Multiple thunderstorm clusters which merge into one large system often spanning 100+ miles during late evening and overnight is known as a mesoscale convective system. One such system crossed the open cornfields of Iowa and Illinois into the Chicago metro overnight causing power outages and flash flooding.

While amazing sights on infrared, their amazing underneath with frequent lightning, torrential rain, hail and quite often strong to damaging winds.

Dangerous situation for Chicago.

Squall line pushing through Chicago.

Via Jon Erdman

In comes the shelf cloud and it’s scraping the Willis Tower.

Credit: Nick Ulivieri‏ @ChiPhotoGuy

An amazing lightning display over Chicago last night.