Heavy downpours produced by strong thunderstorms may occur across a good portion of the Chicago area later this Thursday afternoon/evening into the overnight hours. The National Weather Prediction Center has issued an Excessive Rainfall Outlook that has much of the Chicago area in the Moderate Risk (red-shaded area on the headlined map) for potential flood-producing rainfall in the next 12 to 18 hours.
Storms could “train” – continually redevelop and repeatedly pass over the same area – resulting in some locations receiving as much as 2 to 4-inch from the ensuing storms this evening/overnight. Some of these storms could track over the portion of our area along and north of Interstate-80 that already received from 1 to 2-inches rainfall late last night and early this morning.
A Flash Flood Watch has been issued for much of the Chicago area in effect from 6PM CDT this Thursday evening through Friday morning (dark-green-shaded counties on the map below). Segments of several area rivers are under Flood Warnings/Watches/Advisories for possible minor flooding or bankfull conditions within the next 24 to 48 hours (lighter-green segments on the map below – also map depicting various rivers in Chicago area below). These forecasts will undoubtedly have to be updated at a later time, depending upon where heavier rains fall.