Drivers were urged to postpone travel in parts of the Chicago area Friday morning as a band of lake effect snow brought snow rates of more than 2 inches per hour to some locations.
The National Weather Service reported central Cook County had seen as much as 5 inches of snow in roughly three hours leading up to the morning commute and urged drivers to "postpone travel" through the area.
Visibility had dropped to about a half-mile for Chicago and suburbs along the lakefront stuck in a heavy band of lake effect snow.
Downtown Chicago was seeing heavy impact from the snow.
"We'll be blunt...the morning commute along the north side of Chicago is going to be bad," the NWS tweeted early Friday.
Chicago's Department of Streets and Sanitation activated a "phase III snow program," sending hundreds of plows out to city streets, with a focus on main roadways first.
Across areas seeing the lake effect snow difficult driving conditions were reported and commuters were urged to "prepare for long commutes this morning as snow piles up."
Illinois' transportation department urged commuters to check roadway conditions before heading out and "as always, allow yourself extra travel time."
Drivers can check https://gettingaroundillinois.com for up-to-the-minute road conditions, the department said.
Just after 7 a.m., Illinois State Police in the Chicago district said they were "handling numerous crashed on the Dan Ryan Expressway due to icy road conditions."
"Please use caution while driving, slow down and move over for emergency vehicles!" the department tweeted.
Slow traffic due to snow was reported for several major roadways across the area Friday morning, including on Interstate 55 northbound between Veterans Parkway and the Veterans Memorial Tollway, on both inbound and outbound I-57 near the Dan Ryan Expressway, on the Kennedy Expressway in both directions between Montrose Avenue and the Byrne Interchange, on the Bishop Ford near the Dan Ryan and on the Edens Expressway between Winnetka Road and Montrose Avenue.
A winter storm warning took effect in Lake County, along with northern and central Cook County in Illinois, at 2 a.m., and will remain in effect through noon on Friday.
DuPage County and Southern Cook County in Illinois, as well as northern Lake County in Indiana, will remain under a winter weather advisory through 10 a.m. Friday.
In Lake County and in parts of Cook County in Illinois, between 4 and 8 inches of snow could fall in the most-impacted areas, but snowfall totals will vary widely across short distances due to the nature of lake-effect snow bands, according to the weather alert.
Those areas outside of the heaviest bands of snow will likely see less than four inches of snow Friday, according to forecasters.
Those areas that are most heavily impacted will see horrendous travel conditions, with visibility reduced to less than a quarter-mile and rapid accumulation rates on roadways that will make it extremely difficult for plows to keep up.
Areas of western Cook County could see less than an inch of accumulation.
In southern Cook County and in northwestern Lake County, 2-to-5 inches of snow are possible, especially in areas close to Lake Michigan. Areas further inland will likely see less than that, officials said.
Motorists are still advised to use caution, and are reminded that travel issues are still possible due to the hazardous conditions.
The snow is expected to move out of the area by late morning and into the early afternoon, according to forecasters.
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