The timing of an incoming winter storm that is poised to dump wet and heavy snow on much of the Chicago area has shifted forward, likely impacting the evening commute.
A winter weather advisory initially slated to begin at 6 p.m. in northern Cook County has been moved up to take effect at 3 p.m. The advisory also applies to Lake and DuPage counties, where the heaviest rates of snowfall are expected between 5 p.m. and 11 p.m., according to NWS Chicago.
In this area, two-to-four inches of snow are expected to fall near the I-88 corridor, with totals of four-to-seven inches of snow possible closer to the Wisconsin border.
The advisory is slated to remain in effect until 7 a.m. Friday.
Additionally, a winter weather advisory took effect for DeKalb County early Thursday afternoon, where the advisory will remain in place until 7 a.m. Friday.
This advisory, which also is in effect for Winnebago, Boone, Lee and Ogle counties, warns of snowfall totals that could approach four-to-seven inches, with the heaviest snowfall likely falling before 9 p.m.
In this advisory, snowfall totals of two-to-four inches are expected near the I-88 corridor, with totals of four-to-seven inches anticipated further north of I-88.
Local
According to the National Weather Service, a winter weather advisory for 3 p.m. Thursday has also been issued for McHenry and Kane Counties, lasting until 7 a.m. Friday.
For these counties, the heaviest snowfall is predicted to fall between 4 p.m. and 10 p.m., with rates likely peaking near one inch an hour by the late afternoon and early evening hours.
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An advisory issued for central Cook County will take effect at 6 p.m. Thursday evening, and will remain in effect until 7 a.m. Friday.
This advisory, which will take effect for the city of Chicago and nearby inner-ring suburbs, warns of snow accumulations between one and four inches, with snowfall rates expected to be the heaviest between 7 p.m. and 12 a.m.
In all areas under a winter weather advisory, the NWS warns that shoveling may be hazardous due to the heavy and wet nature of the snow.
Here's a breakdown from the NBC 5 Storm Team of when and where the system is expected to roll in, and how much snow the Chicago area could see.
Storm Timeline
Forecast models show the wintery system is expected to move into the area beginning around 2 p.m. in DeKalb and McHenry Counties, with precipitation likely in the form of snow.
By 5 p.m., the NBC 5 Storm Team says, the rain is expected to transition to snow to the north. In far southern counties like Kankakee, precipitation is likely to stay in the form in rain, the NBC 5 Storm Team says.
Later in the evening, around 8 p.m. a mix of rain and snow is possible across much of the Chicago area, with wet, accumulating snow closer to the Illinois-Wisconsin border.
According to the National Weather Service, the worst conditions for Northwest Illinois are expected between through the evening commute, between 6 p.m. and midnight, while the worst conditions for Northeast Illinois are likely to occur later, between 8 p.m. and 2 a.m.
"Snow rates are likely to peak near one inch per hour early this evening," an alert from the NWS says. "The expected heavy, wet nature of the snow will make shoveling hazardous."
Additionally, untreated roads could make travel difficult, particularly during the times when the heaviest snow is expected to fall, the NWS says.
According to the NBC 5 Storm Team, just before midnight, most areas with rain are expected to transition to snow, with scattered snow showers continuing overnight, setting up a potentially slick and slippery commute Friday morning.
How Much Snow Could Fall?
"Above-average freezing temperatures will initially result in some melting, but higher snowfall rates (up to one inch per hour) will result in accumulations on roadways this evening," the NWS says.
According to forecast models, snow totals between three and six inches is likely in Lake and McHenry, as well as Northern DeKalb and Kane Counties, with potentially higher totals near the Illinois-Wisconsin border.
In DuPage and central and northern Cook Counties, where a rain-to-snow transition is expected, snowfall accumulations ranging from two-to-four inches is expected.
To the south, in Kankakee county and in parts of Northwest Indiana, less than an inch of snow is expected, as precipitation is likely to stay in the form of rain. However, Lake and Porter counties in Indiana could see between one and three inches, the NBC 5 Storm Team says.
Areas with snow will likely stick around through early Friday morning, with some scattered snow showers still possible at that time.
