CHICAGO (CBS) — The Chicago area is preparing for what’s likely to be the heaviest snowfall of the season starting Thursday night, as some areas could see more than 10 inches by Friday night.

The National Weather Service has issued a winter storm warning, in effect from 6 p.m. Thursday until 9 p.m. Friday for most of northern Illinois and northwest Indiana.

Forecasters said snow likely would begin falling between 3 p.m. and 7 pm. In the Rockford area, between 5 p.m. and 9 p.m. near Aurora and Chicago, and between 7 p.m. and 11 p.m. in far southern suburbs and northwest Indiana.

Snow was expected to begin tapering off Friday afternoon or Evening.

The heaviest accumulations were expected between Interstate 80 and the Wisconsin state line, where totals could reach 6 to 10 inches. Some areas could see up to a foot.

Snow totals were expected to be much lower south of Interstate 80.

With so much snow on the way, local and state road crews were planning for a very busy start to the weekend, in an effort to keep roads clear.

The Illinois Department of Transportation maintains a fleet of 1,700 trucks used to plow and salt nearly 16,000 miles of Interstates and other state roads across Illinois when it snows.

Last year, IDOT used more than 300,000 tons of salt.

Meantime, the Chicago Department of Streets and Sanitation also was expected to deploy its full fleet of more than 300 plows Thursday night. When it snows, the city starts by plowing and salting the city’s main streets and Lake Shore Drive until the snow stops, then starts clearing side streets.

Given that this storm is expected to last a full day, some side streets might not get plowed until Friday night.

Meantime, airlines have already started helping passengers prepare for the snow, offering alternatives to passengers worried about getting stuck in the storm.

United and American airlines — the two largest carriers at O’Hare — were waiving change fees, to accommodate travelers who are planning to travel Thursday and Friday.

American is allowing passengers using O’Hare to change their trip to Saturday or Sunday, and pay only the difference in ticket price if they don’t change their seat class or their origin or destination city.

United is allowing O’Hare travelers to switch to another flight departing by Tuesday, as long as they keep the same seat class and origin or destination city.

Airlines at O’Hare have cancelled 55 total flights on Thursday, as of 10 a.m., and 96 flights on Friday.

For flyers using Midway International Airport, Southwest Airlines never charges change fees when passengers need to change a flight. An airline spokeswoman said Southwest has proactively canceled 350 flights at Midway on Thursday and Friday due to the storm. Travelers should visit the Southwest website for details on changing flights, or call 1-800-435-9792 to speak to customer service about re-booking their flights.

Saturday could bring another chance of snow, and there’s a slight chance of snow Sunday morning, before skies clear Sunday afternoon.

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