Winter weather with ice, snow, freezing rain and sleet was expected to ramp up by 6 p.m., Roman said, with winter conditions overspreading the entire Chicago area from around 8 p.m. through midnight. Roman noted 6 p.m. through midnight Wednesday was "peak timing" for freezing rain, sleet and icy roads.

A developing winter storm could bring a potentially crippling ice threat from the Midwest to the Northeast, and the West Coast remains on alert for flooding as a series of atmospheric river storms swamps the region.