Thunderstorms bring threat of heavy rainfall

High temperatures on Friday ran below normal across most of the metro area due to clouds and an east-northeast wind flow. Despite the cool air, thunderstorm development was on the increase across northern Illinois. Wind profiles from local Doppler radar sites showed modest south to southwest flow just 3 thousand feet above the ground. This provided the warm, moist air necessary for storm development. Similar conditions are expected through Saturday night, maintaining the likelihood of additional waves of thunderstorms. Though there is a marginal risk stronger storms may produce brief damaging wind gusts, the primary concern will be heavy rainfall. Portions of the area may receive two or more inches of rain Saturday and Saturday night.