Rain, thunderstorms spreading over the Chicago – heavy rainfall possible

Rain will spread into westernmost portions of the Chicago are this Friday evening and overspread the entire area tonight. A few thunderstorms will be embedded in this widespread band of rain.  Rain could change over to wet snow before ending from the west Saturday morning.

Heaviest rains on the order of an inch to near 2-inches in some spots will occur along and south of Interstate-80 – amounts diminishing the farther you go north to around a quarter-inch likely in counties adjacent to the Illinois-Wisconsin state line.

Rivers have been slowly falling with minor flooding on segments of the Pecatonica and Rock Rivers and the Fox River running close to bankfull. Tonight’s anticipated rainfall will likely cause the Illinois, Kankakee and Iroquois Rivers along and south of Interstate-80 to rise – ultimately some minor flooding could occur if rains on the high-end of the forecast (1.5 to 2-inches) materialize. Rivers farther north could experience some minor rises.

Shown below, the Excessive Rainfall Outlook indicates a good portion of our area , especially along and south of Interstate-80 is in a Slight to Marginal Risk of excessive rainfall (yellow and green-shaded respectively) that could lead to localized flooding.

Excessive rainfall for the period ending 7AM CDT Saturday…

Day 1 Excessive Rainfall Forecast

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