A Winter Storm Watch has been issued for the Chicago area for Saturday.

Counties include Boone, Cook, DeKalb, DuPage, Grundy, La Salle, Lake, Lee, Kane, Kendall, McHenry, Ogle, Will and Winnebago

Widespread blowing snow could significantly reduce visibility, especially along the Lake Michigan shoreline.

The storm is to follow a 40+-deg Friday–so it won’t appear Friday that wintry weather is imminent–but all evidence suggest to the contrary–that a decidedly wintry turn is likely this weekend and that it would be wise to monitor travel plans carefully.

Interactive Radar: Track showers and storms here

The onset of its precip doesn’t occur until Sat afternoon and is likely to fall through Saturday night amid high winds and into Sunday morning.

It could present significant travel impacts in and around Chicago and could generate the season’s most significant snowfall in the Chicago metro area to date.

THU AM: I expect my NWS colleagues to issue a WINTER STORM WATCH later today or tomorrow AM. The exact track will be better defined in the next 24 hrs, but right now a rather high probability (70%+) of 4″+ bisects the Chicago area. #ilwx #snow @WGNNews pic.twitter.com/6H18vB0Oo9

— Bill Snyder (@billyweather) December 30, 2021

Latest Watches and Warnings

The storm’s precipitation appears likely to be “lake-enhanced”. That means lake moisture may well contribute to the system’s snowfall in or close to Chicago. The change in air temps from the lake surface to a mile above the lake are forecast to drop 25-30-deg.

That rate of temp decline is quite high and that’s quite important. Faster than usual drops in temp through that first mile of the atmosphere encourage moisture off the lake surface to sweep into the storm’s already generous supply of moisture. That can affect any final snow accumulations which occur. The suggestion from current model runs is that the weekend system’s heaviest snow totals could occur in the counties of northeast Illinois and, perhaps, far northwest Indiana closest to the lake

Full forecast details and more at the WGN Weather Center blog

Modeling has consistently suggested peak winds building in gusts to 35 mph and more Saturday afternoon, Sat night and into Sunday–strongest in open and lakeside areas good grip on the storm’s specifics before looking at accumulation numbers.

A chunk of frigid arctic air is likely to be drawn southward into the Chicago area in the storm’s wake. This means Sunday highs may hold to the upper teens and nighttime readings Sunday night area likely to fall over a fresh snow pack to single digits and that wind chills are likely to drop sub-zero.

This is important. It’s early. The storm is still two days away. No forecast at that time range is yet carved in stone.

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