PITTSBURGH - Snow fell from the Plains across the Midwest yesterday, accumulating as much as a foot in places, as the second wintry storm in a week barreled through on its way to New England.

Tens of thousands of people still had no electricity since the first storm slammed Oklahoma, Kansas and Missouri earlier in the week. That storm was blamed for at least 38 deaths, most resulting from traffic accidents.

Winter storm warnings and watches extended yesterday from Missouri across parts of Illinois, Indiana, Michigan, Ohio, Pennsylvania, New York, Vermont, New Hampshire and Maine, the National Weather Service said. As much as 15 inches of snow was forecast in sections of southern Michigan, with 10 inches possible in Detroit.

Snow started falling early in the afternoon in Pittsburgh but was expected to change to rain and freezing rain.

"We'll have a little bit of everything before the night is over," said Bill Drzal, a National Weather Service meteorologist in Pittsburgh.

Pittsburgh could get an inch or two of snow, but areas to the north and east could get as much as 12 inches through tonight, according to the weather service.

In Chicago, more than 200 flights were canceled because of the weather at O'Hare International Airport, and other flights were delayed 30 minutes to an hour, said Gregg Cunningham, spokesman for the Chicago Department of Aviation. The problem was limited visibility in the falling snow, said Robin Urbanski, a United Airlines spokeswoman.

Concern about the approaching storm also led the University of Connecticut to cancel today's winter commencement ceremony. About 850 undergraduates had expected to receive diplomas, but school spokesman Richard Veilleux said officials were concerned about the safety of the students and their families and other guests on slippery roads.

Freezing rain was the culprit earlier in the week, coating streets, windshields, tree limbs and power lines with ice as thick as an inch in Kansas, Oklahoma and Missouri.

Oklahoma, hardest hit by the earlier storm, got only cold, light rain early yesterday, turning to snow during the morning. One to 3 inches of snow was forecast.

Neighboring Kansas, however, had as much as a foot of snow yesterday morning, and the Highway Patrol reported Interstate 70 in central Kansas was snowpacked.

More than 2,300 people were in Kansas shelters yesterday because of the power failures and the fresh snow, said Sharon Watson, spokeswoman for the state Adjutant General's Department.