Tuesday’s Supercell That Slammed Northern Illinois And Indiana Had The Perfect Conditions For Sustained Intensity

Why Severe Weather Was Worst In Illinois, Indiana

March 10 brought significant weather from the Southern Plains to the Midwest. Most notable was the supercell that brought consistent warnings as it moved across northern Illinois and Indiana.

The Conditions Were Perfect

The reason we saw multiple long-duration storms across this region is because a stationary boundary was draped over the area.

A stationary front is a boundary between warm and cold air that isn’t moving much, if at all. This allowed for warm, moist air surging north from the Gulf to slam into the cool air moving south over the Great Lakes.

With warm air being less dense, it rises and cools, leading to cloud - and eventually - storm formation.

There was also a powerful jet stream moving through the upper atmosphere. Jet streams provide the ingredients in the upper atmosphere, but you still need what was occurring at the surface to get those powerful, tornado-producing storms.

Fascinating Little Tidbit

There is something else that I wanted to bring your attention to. Check out the graphic below:

You can see where that stationary boundary was located. All the tornadoes were south of it. This is because on the colder side, the cold air served as an inhibitor of tornado development.

You still have hail on that northern, cooler side of the boundary. But there was no chance for tornadoes there. You can literally see the streaks of tornado reports and hail reports from the movement of strong storms.

Now begins the recovery process for the communities impacted, which will take time.

Rob Shackelford is a meteorologist and climate scientist at weather.com. He received his undergraduate and master’s degrees from the University of Georgia studying meteorology and experimenting with alternative hurricane forecasting tools.