CHICAGO — A winter storm moving across the Great Lakes dropped up to a foot of snow in some areas Friday, creating treacherous driving conditions, closing schools, and forcing the cancellation of hundreds of flights.
The National Weather Service issued winter-weather warnings and advisories across the upper Midwest. The snow that began falling late Thursday afternoon continued through Friday as the storm moves east.
A section of Interstate 94 in southwestern Michigan was blocked after dozens of vehicles crashed amid heavy snowfall Friday. State Police said about 50 vehicles were involved in the pileup in the highway’s eastbound lanes just east of Kalamazoo.
Several cars and trailer trucks slid into each other or into the ditch along the highway. No serious injuries were reported.
In Chicago, Mayor Rahm Emanuel said the city was prepared for three more rounds of snow through the weekend after crews dealt with 6 to 7 inches overnight Thursday.
‘‘The good news is we’re tried and tested here,’’ he said. ‘‘We’re up to it.’’
About 750 flights were canceled at Chicago’s O’Hare International Airport and about 300 flights were canceled at Midway, the Chicago Department of Aviation said Friday. More than 200 flights were canceled at Detroit Metropolitan Airport.
American, United, Delta, and Southwest airlines warned travelers to expect more flight cancellations to and from Minnesota, Michigan, Wisconsin, Illinois, Indiana, and Ohio.
Meteorologist Heather Orow in Grand Rapids, Mich., said Friday morning the storm is ‘‘generally going to be an issue for travel.’’ People should stay off the roads if possible, but if they drive they should expect delays and hazardous conditions.
Several crashes were reported on the roads early Friday in the Chicago and Detroit areas.
Chicago Department of Streets and Sanitation Commissioner John Tully said 300 salt-spreading plows hit the streets late Thursday and would continue their work through the weekend.
Hank Stawasz was out shoveling his driveway, clearing a path for the retiree to exit his home in the Detroit suburb of Livonia.
‘‘It’s part of living in Michigan,’’ a smiling Stawasz said from underneath his Detroit Red Wings winter hat. ‘‘I saw the plows come by, so I figured I’d get a jump on it so I wouldn’t have to shovel it when it’s 4 feet high.’’