Accumulating snow will begin to fall across the Chicago Wednesday afternoon, continuing Wednesday night and Thursday with 2 to 5-inches possible along and south of Interstate-80 (area expected to reach Winter Weather Advisory criteria) – greater amounts possible Thursday night/Friday in Lake and Porter Counties in NW Indiana due to strong north winds causing enhanced lake-effect snow as well as building 10 to 14-foot waves and lakeshore flooding.
Lesser snowfall totals are expected farther north and west in Illinois with only an inch or so possible along the Illinois/Wisconsin border – although lake-effect snows later Thursday/Thursday night could cause additional accumulations in Lake and Cook Counties, Illinois.
During the next 24 to 36 hours, a center of low pressure will move out of eastern Texas northeast through Tennessee and Kentucky up the Ohio River Valley, spreading snow over northern and central Illinois into Indiana, beginning Wednesday afternoon. Another low pressure and associated cold front accompanied by a band of snow will approach our area from the northwest, passing through Chicago Wednesday night.
The combination of the two systems will produce a blanket of snow across the Chicago area – greatest amount initially falling over the area along and south of Interstate-80. Thursday following the cold frontal passage strong northerly winds gusting over 30 mph will develop lake-effect snow showers and build 10 to 14-foot waves primarily impacting the Indiana Lake Michigan shoreline.
Bitter Arctic-source high pressure will spread over our area from the northwest Thursday into Friday with temperatures falling through the 20s later Thursday, dropping below zero with frigid sub-zero wind chills by Friday morning. Highs on Friday look to be in the teens.