A cold front that passed through our area today will sink south, becoming nearly stationary along the Ohio River Valley later tonight, Chicago positioned on the leading edge of a following huge cold high pressure centered over the northern and central plains extending east into the western Great Lakes and Midwest. Low pressure developing on the frontal boundary in the southern plains will then move up the Ohio River Valley, passing to our south and east Tuesday night.
With Chicago in the colder air, precipitation associated with the low pressure will be in the form of wet snow as it spreads over our area Tuesday, perhaps accumulating a little across the portion of our area mainly south of Interstate-80. Temperatures are expected to drop through the 30s into the mid and upper 20s later Tuesday night and Wednesday forenoon with the entire Chicago area encompassing northeast Illinois into northwest Indiana under a Freeze Warning. Note on the headlined map Freeze Warnings (dark blue-shaded areas) extend from the Texas Panhandle all the way northeast across Illinois into Indiana, Lower Michigan and western Ohio.
We will probably continue in the cold high pressure again Wednesday night/early Thursday, likely necessitating another Freeze Warning.