A Winter Weather Advisory calling for generally 2 to 3-inches of new snow will be in effect for most of the Chicago area from early Monday morning until Monday afternoon (purple-shaded counties on the headlined map). A new band of accumulating snow will approach from the northwest later tonight, spreading over northeast Illinois into northwest Indiana by Monday morning, impacting the early morning commute.
The system will arrive first in westernmost sections of the Chicago area shortly after midnight and reach northwest Indiana a little before sunrise Monday. Significant accumulations will most likely occur Monday forenoon. So if you will be driving early into mid-morning Monday, prepare for a potential slow-go under slippery conditions.
The Advisory will go into effect at 3AM CDT west of Chicago and about 5AM CDT in NW Indiana. Snow should effectively end in Illinois by noon, but will probably continue in NW Indiana the remainder of the afternoon and be a little heavier due to the initiation of lake-effect snow showers. The NW winds will likely continue to drive lake-effect snow showers in NW Indiana Monday night into Tuesday.
Winds shift to the northwest Monday afternoon ushering in a renewed influx of Arctic-source high pressure. The cold air mass will ride the gusting NW winds into our area later Monday, settling over the Midwest and Great Lakes Tuesday and Wednesday, holding daytime highs in the lower teens and the clearing skies along with fresh snow cover allowing overnight temps to below zero – the coldest temps, well below zero look to occur Wednesday morning. Sub-zero wind chills will likely occur from Monday night into Wednesday morning.