It looks like Lake and McHenry Counties could see snowfall totals of 6 to 10 inches by Wednesday morning.
A winter storm warning is now in effect for both counties until 6 a.m. Wednesday, according to the National Weather Service in Chicago.
"Snow will significantly slow travel and make it dangerous at times through the early evening commute, so persons planning travel should anticipate extremely elevated travel times," according to the National Weather Service, noting that "temporary white-out conditions with near-zero visibility" are possible.
Snowfall amounts in excess of 4 or 5 inches have already been reported across northern Illinois.