lake effect snow

Timeline: When Lake-Effect Snow is Expected to Hit Cook County, NW Indiana

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Lake-effect snow is expected to hit portions of the Chicago area late Thursday night and into Friday morning, with some locations potentially seeing six or more inches of snow before all is said and done.

According to forecast models, areas near Lake Michigan in central and southern Cook County, as well as portions of northwestern Lake County in Indiana, are expected to be hit with the snow beginning around 11 p.m. Thursday night, and that system could potentially linger through noon on Friday.

While most areas in the impacted region could see 2-to-4 inches of snow, some localized snowfall totals in excess of six inches are possible, according to forecast models, along with intense snowfall between 1-to-2 inches an hour Friday morning.

Here is what we know about the timeline of the weather system.

Thursday Evening:

Temperatures are expected to decline throughout the evening Thursday as a mass of cooler air sweeps through the area.

That air mass could potentially cause widely scattered snow showers across northern Illinois, but the real threat is expected to come in behind that air mass, as a “fetch” will draw in warm, moist air from over Lake Michigan and deliver it to the Chicago area by late Thursday evening.

Thursday Night/Friday Morning:

When that “fetch” takes place, lake-effect snow bands are expected to develop late Thursday night and into Friday morning, according to the National Weather Service.

In response to that snowfall, the National Weather Service has issued a winter storm watch for central and southern Cook County, along with northern Lake County, beginning on Thursday night and running through noon Friday.

Snow-covered roads are a likely hazard, with Interstates 80, 90 and 94 in northwest Indiana potentially impacted by the nasty weather.

The snow is expected to intensify overnight, with NWS calling for the worst conditions to develop between 2 a.m. and 10 a.m., snarling the morning commute and dumping more than an inch of snow per hour in some locations.

Visibility will likely be reduced to less than half a mile in some locations, according to forecast models.

Late Friday Morning:

The snow will likely start to taper off in the late morning across the area, but not before leaving behind accumulations between 2-to-6 inches in some locations.

Portions of Cook County that are near Lake Michigan, including parts of Chicago, will likely see the heaviest snow, along with portions of extreme northwest Lake County in Indiana.

Areas further to the west could see some snow, but it likely will not be as intense as areas closer to the lake. The National Weather Service says there is a chance of some snow falling in far eastern Will County, with a lower chance of snow being experienced in far eastern DuPage County, central Will County and even into northern Kankakee County.

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