https://www.spc.noaa.gov/products/outlook/day1otlk.html

" ...SUMMARY...
Numerous severe thunderstorms are likely this afternoon into tonight
across parts of the Upper Midwest southward across the lower
Missouri Valley into central Great Plains. Initially this may be
accompanied by a risk for large to giant hail and a few strong
tornadoes, before severe wind gusts 60 to 90 mph become the
most prominent hazard by this evening."

"Recent model guidance continues to show the development
of discrete supercells later this afternoon ahead of the front over
parts of central/northern WI near the low, and farther south in the
vicinity of eastern IA into adjacent portions of WI/northwest IL.
All hazards will be possible with this potential activity, including
the possibility for an intense tornado. Large to giant hail will be
possible with supercells. Other storms likely to evolve quickly
into a band of severe thunderstorms will develop farther west and
push east coincident with the front. Damaging wind gusts will tend
to become more prevalent during the evening with linear storm modes.
Some tornado risk may continue into the evening as maturing bands of
storms yield a threat for bowing segments and embedded mesovortices,
before this activity gradually diminishes late as it moves east into
IN/Lower MI late."

Biggest tornado risk is SW Wisconsin and NE Iowa with bits of NW Illinois in supercells ahead of a line of storms.

However, a very strong risk of damaging straight-line winds for almost all of northern and central IL. Chicago + burbs, STL + burbs, and the Paign are all right on the edge of the highest wind threat (60-80mph possible).

Should have the possible supercells popping in eastern Iowa near Waterloo & Cedar Rapids by early afternoon and heading ENE into SW Wisconsin. Everything will eventually coalesce into a line by early evening and march across northern IL and northern MO. Chicago area sometime 7-10pm. Paign, 8-midnight. STL, 9-1a.