Big Hail, Isolated Tornadoes in the Midwest Tomorrow (Thu, Mar 26)

I'm not saying Illinois is going to break their 2-week old hail record again tomorrow, but I am saying we're likely to add yet another day in 2026 with significant 2"+ hailstones being recorded in Illinois and neighboring Indiana, perhaps into northwest Ohio or far southern lower Michigan.

We'll see quite a volatile warm sector across northern Illinois and Indiana on Thursday, March 26th with afternoon temperatures soaring into the mid 80s with dew points in the mid 60s. In the absence of a big upper level trough, temperatures aloft aren't terribly cold but this is still good for around 1750-2250 j/kg of ML CAPE and some really steep lapse rates in the lower and middle levels. Even with all of that, a stout cap will keep a lid on thunderstorm development until the late afternoon or early evening hours, and may limit storm coverage south of the cold front.

Numerous severe storms are likely on Thursday evening, but the more storms favor the cold side of the boundary, the more we'll lean into a hail-only risk. More storms in the warm sector, and we're ramping up the tornado risk!

I think a big key to these significant hail setups early this spring in the Midwest has been the expansive drought across the Southern Plains and southwest U.S.

We saw a similar geographic/atmospheric setup in early 2023 with hot, dry air being advected into the Midwest by areas of low pressure tracking out of the Plains. This hot dry air is drawn into the region just above the surface, serving as an impressive EML (elevated mixed layer), something more commonly observed across the Great Plains where big hail is a more frequent hazard. We get hail in the Midwest, don't get me wrong, but peruse most of our bigger severe weather outbreaks of the past and you'll probably find a bunch of 1.75" hail reports. To be seeing 3" to 4" hail frequently in Spring 2026 is very anomalous in Illinois (and Indiana).

We aren't necessarily getting rid of the massive ridge out west this week, but we're flattening it out a bit. A subtle disturbance running along the base of core of stronger jet stream flow along the US/Canada border is the catalyst to kicking off scattered storms along the stationary frontal boundary draped near Interstate 80 across northern Illinois and Indiana on Thursday afternoon.

A strong southwesterly low-level jet running along and south of the frontal boundary will elongate hodographs and support supercell development and perhaps even encourage tornado production from any supercell that can form near and remain south of the colder air north of the front. The front will begin to move south quickly during the late evening and early overnight so southeast storm motion and a right-turning supercell will be necessary to avoid being undercut.

I think the most likely scenario is scattered supercell storms forming on or just to the cold side of the boundary with big hail being the primary risk. Still, the warm sector across northern/central Illinois and Indiana will support supercells and tornadoes if a robust storm can erupt on the warm side and stay there for an hour or two. This seems most likely somewhere from around Pontiac/Kankakee IL to Fort Wayne IN.

I'll get more detailed on timing and the magnitude of hail + tornado risk on Thursday morning.