A storm system is moving across the Upper Midwest this evening with warm air aloft overrunning sub-freezing air at the surface, and resulting in a freezing rain event for the Chicago Metro Area. Precipitation is already spreading into the region this evening, as can be seen on the recent precipitation-type radar image, with red colors indicating freezing rain. You’ll even notice there have been some recent lightning strikes southwest of the area toward Peoria!
Freezing rain will continue through the overnight period before tapering off between roughly 6am-8am Wednesday morning. Ice accumulations will make for a hazardous Wednesday morning commute, especially on bridges and elevated surfaces. Some parts of the metro area could see ice accumulations of 1/4″ or higher. The next image from the HRRR model shows projected ice accumulations overnight (image source: College of DuPage).
In addition to difficult road conditions, downed trees and power lines will also be a hazard, as these type of storms usually result in widespread power outages.
After the freezing rain comes to an end Wednesday morning, temperatures will slowly rise from near freezing into the mid/upper 30s for the remainder of the day, which should allow for improvement on the roadways despite skies remaining cloudy.
The next round of precipitation will then arrive Wednesday night and Thursday, but fortunately this will be all rain (of the liquid variety), with temperatures warming up significantly into the 40s during the day Thursday.