American, United, Delta and Southwest airlines warned travelers to expect more flight cancellations to and from Minnesota, Michigan, Wisconsin, Illinois, Indiana and Ohio.

The Associated Press

CHICAGO — A winter storm moving across the Great Lakes that’s forecast to drop about a foot of snow in some areas created treacherous driving conditions Friday, closed schools and forced 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 was expected to continue through Friday as the storm moves east.

In Chicago, Mayor Rahm Emanuel said the city was gearing up for three more rounds of snow through the weekend after crews dealt with 6 to 7 inches overnight.

“The good news is we’re tried and tested here,” he said. “We’re up to it.”

As of Friday morning, the National Weather Service received reports of between 9 and 11 inches of snow over a 24-hour period in Fort Dodge, Iowa. Eight inches were reported in parts of northern Illinois and in New Carlisle in northern Indiana.

Snow across southern and central Michigan ranged from 7 inches on the western side of the state to more than 2 inches in the Detroit area.

Hank Stawasz was out shoveling his driveway by hand, 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.”

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 reported Friday morning. More than 200 flights were canceled at Detroit Metropolitan Airport in Romulus, Michigan, by early Friday.

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, Michigan, 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.

Slide-offs and crashes were reported on the roads early Friday in the Chicago and Detroit areas. A multi-vehicle crash that closed a stretch of eastbound Interstate 94 near Ann Arbor, but no severe injuries were reported.

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.

The expectation of up to 12 inches around Chicago prompted officials to close the city’s public schools to about 390,000 students Friday. Classes were also canceled in the city’s suburbs. CPS officials said Friday morning they expected classes to resume Monday.

Schools in Detroit shut for the day along with Wayne State University in Detroit and other schools across Michigan.

Students in the Milwaukee Public School District — Wisconsin’s largest school district — have Friday off. Schools across Nebraska and Iowa closed or delayed the start of classes.