Flash Flood Watch no longer in effect – showers and thunderstorms weaken this Sunday morning

Update 5:50AM CDT…

The Flash Flood Watch for portions of the Chicago area along and north of Interstate-80 is no longer in effect. A few showers/thunderstorms may occur mainly south of Interstate-80 today and then possibly spread back over our area again later Sunday night.

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The Flash Flood Watch (green-shaded counties on the highlighted map above) will remain in effect overnight into Sunday morning for Chicago area counties along and north of Interstate-80, as a Mesoscale Convective System/Complex initiating over the southeast corner of Iowa will spread strong thunderstorms with heavy downpours east-northeast into western Illinois and the Chicago area tonight  and early Sunday morning. Storms will continue to form out to our west and track east – likely “training” repeatedly over the same locations, resulting in 1 to 2-inches of rain or more and subsequently localized flooding.

A west-east-oriented stationary frontal boundary remains positions through southern Iowa into central Illinois has become increasingly unstable as warm moist low-level southwest flow lifts over the front, triggering clusters of thunderstorms that will develop over/steer into our area overnight. Hail could fall from some of the stronger storms, but the main impact looks to be the potential torrential flood-producing rains.

The National Storm Prediction Center has issued a Thunderstorm Probability map for overnight, which has the 70%-plus chance of thunderstorms within 12 miles of a given location centered over northern Illinois into northwest Indiana…see map below.

Thunderstorm Outlook until 7AM Sunday…