Chicago, Illinois - A heavy, wet winter snowstorm made travel treacherous on Friday in the Midwest and Northeast and was blamed for at least 10 traffic deaths.

Nearly 7 1/2 inches of snow was reported at Chicago's O'Hare International Airport before the front moved out of the area Friday. About 500 flights were canceled at O'Hare, which canceled 600 flights Thursday and housed hundreds of stranded travelers who spent the night awaiting planes from other cities also affected by the storm.

At least 12 inches of snow was reported in Springfield by Friday morning, said National Weather Service meteorologist Gino Izzi. Ten inches fell in Bloomington and southern Illinois saw as much as 11 inches dumped near Palmyra in Macoupin County northeast of St. Louis.

"If you don't have to be out here, don't," Ty Wilson, a very wet Chicago bicycle messenger, said as he stopped along a slushy street between morning deliveries.

The storm brought snow, freezing rain and sleet to the Northeast, where arriving flights at Newark Liberty International Airport were seeing delays of up to three hours Friday afternoon. Arrivals were delayed by two and a half hours at La Guardia Airport, two hours at Philadelphia International Airport and an hour and a half at Kennedy Airport, according to the Federal Aviation Administration's Web site.

Along the nearly 500-mile-long New York State Thruway, troopers reported more than 200 accidents - compared with between 10 and 15 on a typical clear day.

At least four people died in traffic accidents Friday on ice-slicked Hudson Valley roads - three when their car slid into an oncoming sanding truck in East Fishkill, the fourth in a head-on collision in the town of Goshen. Six people died on Illinois roads in crashes Thursday and Friday.

Hundreds of schools in Michigan canceled classes and roads were snow covered and slick. The weather service said 1 to 5 inches had fallen in parts of southern and southeast Michigan by early Friday.

Another storm system made roads impassible in parts of the Pacific Northwest. In Washington state, a 70-mile stretch of Interstate 90 remained closed because of the avalanche danger at the Snoqualmie Pass in the Cascade Range.

The state's main east-west traffic route across the Cascades had been closed for all but six hours since Tuesday morning - the lengthiest closure for the pass since 1997.

Recent storms have dumped more than 5 feet of snow on the pass, and more was expected by Saturday morning.

Crews used dynamite to dislodge unstable snow near the highway. State Department of Transportation administrator Don Whitehouse gave no prediction on when the freeway might reopen.

Associated Press writers Jim Suhr in St. Louis, David Mercer in Champaign, Ill., and John K. Wiley in Spokane, Wash., contributed to this report.