With a winter storm warning impacting the entire Chicago area set to go into effect Thursday morning, Metra has announced it will run a "modified" schedule and reduce service on its lines on Friday.
"With blizzard conditions forecast for the Chicago region and many regular commuters already beginning their Christmas holidays, Metra will reduce service on most lines across its system on Friday, Dec. 23," a statement from Metra read, adding that it will operate its normal weekday schedule on Thursday. Specific schedule information can be found here.
According to forecast models, travel conditions are expected to "rapidly deteriorate" by Thursday evening rush hour.
Blizzard conditions are possible Thursday afternoon and into Friday morning, according to the National Weather Service, with "brutal" travel conditions anticipated.
Still, according to NBC 5 Storm Team Meteorologist Paul Deanno, the "window of concern" will likely be between 8 p.m. Thursday and 12 p.m. Friday. During that period, the snow will likely become moderate to heavy at times, paired with wind gusts of up to 55 mph and visibility near zero at times. Not to mention wind chills of up to -35 degrees.
"Even when the snow stops, winds will still be strong," Deanno said. "So snow will be blowing around all over the place, making it look like it’s still snowing."
Winter Storm Warning
The entire Chicago area has been upgraded to a winter storm warning, with timing shifting by location.
The winter storm warning will begin at 9 a.m. Thursday in McHenry, DeKalb, Kane, LaSalle, Kendall and Grundy counties, according to the NWS. The warning will take effect in Lake, DuPage, Kankakee, Cook and Will counties in Illinois at noon and in Lake, Newton and Jasper counties in northwest Indiana starting at 3 p.m. CT.
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It will remain in effect across the area until 6 a.m. Saturday.
Porter County, Indiana will see a blizzard warning beginning at 3 p.m. CT Thursday and continuing until 6 a.m. Saturday. The National Weather Service noted that such a warning is not based on snowfall amounts, but instead on winds and visibility.
According to the warning, "falling and blowing snow will result in white out conditions with zero visibility at times, making travel extremely difficult, if not impossible."
Wind gusts of up to 55 mph could also lead to power outages and ice-covered roads are possible as temperatures "rapidly fall" late Thursday afternoon and into early Thursday evening. From Thursday night and into Friday, wind chills as low as 35 degrees below zero are likely.
How Much Snow is Expected?
While the current forecasted snow totals may not seem noteworthy, "it's not just the snow," Deanno said. It's the combination of snow, high winds and dangerously cold wind chills.
Still, some areas could see more than 8 inches of snow, while others see closer to 3 inches, though projections continue to shift in the lead-up to the event.
Deanno also noted that wind could play a role in how much snow is left behind in your area. While some locations may see several inches of snow, that may not be the total left behind due to the high wind gusts blowing the snow to other locations.
Dangerous Travel Conditions
The National Weather Service is warning travelers and motorists -- whether they're taking trip out of town or just down the road -- that travel conditions during the height of the storm could be potentially "life-threatening."
The storm comes amid one of the busiest travel times of the year. According to AAA, 113 million Americans -- 5.8 million in Illinois -- are expected to travel 50 miles or more between Dec. 23 and Jan. 2. Wednesday and Thursday alone, the Illinois Tollway estimating that 1.7 million vehicles are expected to use the tollway system.
And according to the Chicago Department of Aviation, approximately 2.9 million air travelers are expected to pass through O'Hare and Midway International Airports between Dec. 21 and Jan. 2.
What Are Blizzard Conditions?
According to NBC 5 Storm Team, a specific set of conditions must be met in order for a weather pattern to be considered a blizzard. They include snow or blowing snow, wind gusts of at least 35 miles-per-hour, and visibility of a quarter-mile or less.
All three of those conditions must be present for at least three hours for a storm to be labeled a blizzard, NBC 5 meteorologists report.
According to NWS, the snowiest Christmas on record for the Chicago area took place in 1950, when the city say just over five inches of snow.
