A strong winter system is expected to arrive in Illinois overnight, bringing with it snow accumulation topping 6 inches or more in some parts, gusty winds of up to 50 miles per hour, and even blizzard-like conditions, the National Weather Service said.
The snowstorm is expected to move out of the Chicago area by midday Saturday, according to the NBC 5 Storm Team, tapering in the evening.
After that, the coldest air of the season -- or perhaps the last five years -- is expected to move in, NBC 5 Meteorologist Kevin Jeanes said, with days-long wind chills as low as -30.
"The coldest air of the season is expected to arrive towards Sunday and into next week, the NWS said. "The coldest wind chills during this time may fall below -30 °F at times, especially Sunday and Monday nights!"
Wind chills are expected to be between -20 and -30 Sunday through Wednesday, Jeanes said, along with wind gusts of between 20 and 30 miles per hour.
According to Jeanes, this could set the stage for those days to be the coldest Chicago has seen in five years.
Upcoming cold will be 'brutal'
Local
High temperatures Thursday are expected to be in the upper 20s to mid 30s, and remain in the mid 30s Friday, when the snow is expected to arrive.
By Saturday however, those temperatures, along with wind chill values, are expected to start their descent.
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Jeanes reported "feels-like" temperatures Saturday evening will be close to -6. By Sunday morning, it will feel even colder, at -18.
It gets even lower from there.
Wind chill values are expected to be -25 Sunday night, -29 Monday morning, and -35 Tuesday.
It's not until Thursday that wind chill values will get above zero, with "feels-like' temperatures closer to the 20s, Jeanes said.
Winter Storm Watch soon in effect
According to the National Weather Service, a winter storm watch will go into effect in DeKalb, LaSalle, Kendall and Grundy counties on Thursday night. McHenry, Lake, Kane, DuPage, Cook, Will, and Kankakee counties in Illinois, as well as Lake and Porter counties in Indiana, will go under the watch at 6 a.m. Friday morning.
All counties will be under the watch until 12 p.m. Saturday, according to NWS officials.
The main threats with the storm will be snow accumulations, which could exceed six inches in some locations.
The other threat will be the wind, with ferocious wind gusts in excess of 40-to-50 miles per hour causing blowing snow and “blizzard conditions” in some locations, according to NWS officials.
When will it snow?
NBC 5 Meteorologist Alicia Roman reported snow is likely to begin falling on Friday between 4 and 6 a.m., with wind gusts in the teens.
According to the NWS, a "burst" of heavy snow Friday morning near and north of I-80 is expected to occur, with snow falling at a rate of 1-3 inches per hour.
After 7 a.m., locations south of Interstate 88 will see the snow transition to rain as precipitation across the area will likely lighten before conditions worsen later in the day.
By late morning and early afternoon, more intense, areawide snowfall -- or rain in some parts -- is expected to occur, with winds ramping upwards of 40 miles per hour, the NBC 5 Storm Team said.
Whether this precipitation is snow or rain or a mix of both will depend largely on temperatures, but the transition from rain to snow is expected to take place sometime between 2 p.m. and 5 p.m. across the area.
Friday after 5 p.m., the "worst conditions" of the storm are expected to develop, the NWS added, with blizzard-like conditions expected to form Friday night.
"Strong, southwest winds may gust between 40 and 50 mph Friday night, causing significant blowing and drifting snow," the NWS warned, adding that strong winds along Lake Michigan could create "gale to storm-force winds and very hazardous waves," creating the potential for minor lake shore flooding.
The snow is expected to linger into Saturday, eventually tapering in the afternoon, Roman added.
Snow totals: How much will it snow?
As of Thursday morning, models showed the highest snow totals will likely be in the northern part of the Chicago area, with widespread estimates ranging between 6 and 9 inches, though some locations could see up to 10 inches.
Totals get lower in the southern parts of the region, but much of the totals will depend on how far north the warm air and rain mix during the day.
Overall, area-wide totals between 5 and 7 inches are expected north of Interstate 80 and between 2 and 5 inches south of I-80.
Roman's earliest look at snow totals, which are subject to change, can be found below:
The snow combined with the strong winds could result in dangerous driving conditions and reduced visibility for both the Friday morning and evening commutes, the NWS said.
"Gusty winds could bring down tree branches and power lines," the NWS warned, adding that rapidly falling temperatures Friday might could lead to a flash freeze on untreated surfaces.
The NBC 5 Storm Team is tracking this forecast as it develops. Stay tuned for updates as each system approaches.
