Thursday’s not off to a pleasant start.
Precipitation has arrived on schedule and is occurring in the mixed form predicted— with rain and occasional mixed snow in the city and no travel issues here–all rain is falling farther south–and mainly snow is occurring north and west.
Snow is not yet an issue in Chicago and likely won’t be until tonight.
The scenario unfolding is a complex one with mixed precip across the area much of the day. But colder air is to become entrained in the system late today and tonight switching precip to all snow over time, which looks to be lake enhanced in lakeside counties. Having said that, a wintry mix of precip, with its form switching back and forth from rain to a mix of snow and rain, is to dominate Thursday.
How much snow will we get?
The expectation continues to be that 1 to 5 inches of snow is to fall in a corridor roughly from the I-80 corridor northward.
Two to four inches is likely over much of Chicago proper tonight with an isolated 5 inches total conceivable in a heavier lake snow bursts.
Four to 7 inches is to fall in counties along the Wisconsin line by the time precip winds down late tonight.
A layer of near to above freezing air is in place from roughly 5,000 to 9,000 ft aloft. That had been expected and is why we’re getting a mix of precip–and continue with a mix of precip through the day in the city.
But mainly snow is to fall and begin accumulating to the north and northwest in counties adjacent to the Wisconsin line.
The atmosphere cools tonight here in the city to the point that the northeast winds which build in strength today into tonight, are to sweep moisture off Lake Michigan–likely enhancing snowfall at times in lakeside counties of northeast Illinois and ultimately into northwest Indiana.
More on Snow Projection Models
Among these graphics is a series of hour by hour predictions of the precipitation which is to fall–and the form it is to take (pink shaded areas indicate where the precip is to be mixed–while green areas indicate rain and blue shaded areas indicate where snow is expected) across the area so you can follow the varied precip forms expected and see the change to all snow projected tonight.
Full forecast details at the WGN Weather Center
The models I’ve chosen here are the European Centre’s operation model for the WIDER MIDWEST PICTURE–and the National Weather Service’s 3km high resolution HRRR model. (By the way–the “HRRR” acronym stands for “High Resolution Rapid Refresh” model. It’s run and continually updated on National Weather Service supercomputers on an hourly basis.)