Weather Alerts

Timing: When Might Snow Begin in Chicago Area?

A winter storm watch has been issued for parts of northern Illinois Tuesday afternoon and evening and continuing through Wednesday afternoon

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When will snow start falling and how long will it last in the Chicago area?

Here's a look at timing of the upcoming winter storm and what you can expect:

Winter Storm Watch

A winter storm watch has been issued for parts of northern Illinois Tuesday afternoon and evening and continuing through Wednesday afternoon.

According to the National Weather Service, the watch will include DuPage, Cook, LaSalle, Kendall, Grundy, Will, Lake, Kankakee and Kane counties in Illinois. It also includes Lake and Porter counties in Indiana. The watch was cancelled for both McHenry and DeKalb counties Monday evening.

For Kankakee, as well as Lake and Porter counties in Indiana, the winter storm watch is in effect from Tuesday evening through Wednesday afternoon. Elsewhere, it begins Tuesday afternoon.

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The watch warns of snow totals in excess of 6 inches. According to NBC 5 meteorologist Andy Avalos, totals are expected to range between 4 and 8 inches, though some locations will see higher amounts and others could see lower totals.

When Will It Start?

Tuesday will likely begin with a light mix of snow and rain transitioning to all snow by the afternoon and evening. A few inches of accumulation is possible by Tuesday evening as steady, moderate snow continues overnight.

Wednesday will likely begin with light to moderate snow that will continue into the evening hours, leaving behind several inches of accumulation for many locations.

How Much Snow Will There Be?

Several factors are expected to come into play that will dictate just how much snow the area will see, and where the snow will fall. Beginning Tuesday night, forecast models show the potential for lake enhancement of the snow, meaning that winds off of Lake Michigan could help add moisture to the storm system, causing even more snow to fall.

In addition, it is unclear where the line will eventually settle between rain and snow. Forecast models currently indicate that the line will settle just northwest of Chicago, keeping the heaviest snows in the northwest suburbs. Meanwhile the southern suburbs would see mostly rain during the storm, with the rain only turning to snow on Wednesday.

That line between snow and rain could drift north or south, potentially moving the area where the heaviest snow will fall.

Travel is expected to be impacted, as snowfall could exceed one inch per hour in some locations.

Strong winds are also possible with the weather system, with blowing and drifting snow possible during the morning and evening commutes.

Stay tuned to NBC 5 and download the NBC Chicago app for all the latest updates on the approaching storm system.

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