ILLINOIS — A weak squall line is expected to develop along a cold front across Missouri and Iowa on Tuesday before moving into western Illinois during the evening. The storms will have limited instability to work with, but one or two could produce damaging wind gusts, small hail, or a brief tornado. The window for a strong thunderstorm in the marginal risk area runs from 3 p.m. to 8 p.m., and no expansion of the risk area is expected.
Marginal Risk Covers Western and Southwestern Illinois
A Level 1 out of 5 marginal risk for severe storms covers western and southwestern Illinois on Tuesday. The risk area includes Quincy, East St. Louis, and Carbondale, with its eastern edge reaching near Springfield and Galesburg.
The marginal risk also extends west across much of Missouri and into parts of eastern Iowa, where the squall line is expected to first develop. Areas farther south into southern Missouri and Arkansas are also included in the low-end risk zone.
General Thunderstorms Possible for Chicago, Peoria, and Champaign
The rest of Illinois falls under a general thunderstorm area, meaning storms are possible but not expected to turn severe. This includes Rockford, Moline, Peoria, Bloomington, Champaign, Effingham, and Mount Vernon.
The Chicago area, along with DeKalb, Aurora, and Kankakee, also sits within the general thunderstorm zone. Residents in these areas may hear thunder and see brief downpours, but the threat for damaging storms remains low.
Storms Weaken as They Move East Tuesday Night
The squall line is expected to reach western Illinois Tuesday evening, but storms should begin weakening as they move east and run out of instability. The best chance for any strong storm stays between 3 p.m. and 8 p.m. in the marginal risk area…