The snowstorm that staggered the western Plains rolled over the Midwest yesterday, dumping up to a foot of snow, forcing airlines to cancel flights because of poor visibility, and sending cars sliding off icy highways.

Thousands of people in Missouri and Oklahoma still had no electricity after a Christmas ice storm ripped down power lines, and hundreds of residents of West Memphis, Ark., and Millington, Tenn., could not return to homes that were flooded Christmas morning.

On the western Plains, as much as 34 inches of snow fell without warning in the Colorado foothills. More than 100 miles of Interstate 25 remained closed by snowdrifts in Wyoming.

Locally, road crews throughout the region were preparing for an overnight snowfall. Only an inch was expected by 7 a.m., although forecasters said heavy snow showers could continue throughout the day. {Story on Page C1.}

Fifteen inches of snow fell in sections of Minnesota, up to 14 inches in parts of Wisconsin, a foot in parts of Iowa, and smaller amounts in Illinois, Michigan and Indiana. Snow with sleet and freezing rain spread across Ohio and into the Delaware-Maryland area yesterday.

As the storm moved eastward, about two inches of snow was reported on the ground in parts of Ohio by early evening, and up to six inches more was possible, forecasters said.

The National Weather Service posted winter storm warnings for heavy snow last night over Cape Cod and parts of Pennsylvania, New Jersey, Maryland, Delaware, Virginia, West Virginia, Ohio and Michigan, while snow advisories were posted in much of the rest of the Northeast Corridor and parts of the Great Lakes region.

The snowstorm's arrival in northern Illinois was punctuated by lightning and thunder yesterday. By mid-afternoon, six to 13 inches of snow had accumulated, and tree branches sagging under the weight of the wet snow caused temporary blackouts for hundreds of customers, Commonwealth Edison Co. officials said.

United Airlines and American Airlines canceled many flights into and out of Chicago's O'Hare International Airport until afternoon, when the snow tapered off to flurries.

At times, visibility was only one-eighth of a mile, said Marjorie Kriz of the Federal Aviation Administration.

On Sunday, when the storm closed Denver's Stapleton International Airport for 7 1/2 hours, it was the airport's first complete shutdown since 1983.

Delays affected more than half of the 200,000 travelers Sunday and yesterday, airport spokesman Norm Avery said.

United, one of Stapleton's two major carriers, canceled nearly one-fourth of its 1,800 flights Sunday, and Continental, the other, canceled 250 of its 1,600 flights.

All four runways were open this afternoon, but Avery said the passenger backlog will not be cleared up before Wednesday.

As is common in the Rockies, the storm focused its power along the east front of the mountains, with the largest snow accumulations found south and east of Denver. Along the continental divide and the western slopes, the storm was disappointing: Ski resorts such as Aspen and Vail reported only five inches of new snow at the most.

But the major mountain ski areas had received nearly two feet of new snow in the week before Christmas, and all reported excellent conditions.

In northwestern Illinois, about 150 people spent Sunday night at Stockton High School because freezing rain that fell ahead of the snow covered highways with ice.

"On one stretch of roadway about six miles long, we had about 30 or 40 cars abandoned after they became stranded and couldn't get anywhere on the ice. The salt trucks had to go up and down the hills backwards because that was the only way they could get any traction. Then more rain fell on top of the salt and froze," JoDaviess County Sheriff Steve Allendorf said.

A 17-car pileup closed U.S. 23 for about two hours in Michigan's Livingston County, northwest of Detroit, with no injuries reported, state police said.

In the Chicago area, "We've got a lot of abandoned cars and a lot of cars sliding into other cars and into ditches and poles," state Trooper Joe Giron said yesterday.

The Minnesota Transportation Department had to pull its snowplows off parts of Interstate 90 in the southwestern part of the state Sunday evening because they could not keep up with the snow, said State Patrol dispatcher Les Muck in Marshall.

Plowing resumed early yesterday. The Fairmont area had up to 15 inches of snow, the weather service said.

Motel owner Ernie Wingen in Blue Earth, Minn., said he had no time to sleep during the night while he presided over his "40-40 Club" -- 40 rooms booked, 40 parties turned away.

"We have people sleeping all over the floors, in the lobby, down the hallways," he said.

At Limon, Colo., east of Denver, about 2,000 people took shelter Sunday night in the town hall, three churches, a school cafeteria and a gymnasium while I-70 was closed by heavy snow, Police Chief Jim Trahern said.

Yesterday's rush hour in Denver was relatively problem-free, mainly because so many people were unable to dig out their vehicles. Some businesses and Denver courts decided not to open at all.

Utility crews worked to repair power lines broken by the Christmas ice storm.

All four television stations at Springfield, Mo., were off the air over the weekend; one remained without power yesterday.

About 25,000 people across the Ozarks still were without power. Ernest DeCamp, spokesman for Springfield's City Utilities, said it would be Friday at the latest before full power is restored.

In northeastern Oklahoma, Public Service Co. of Oklahoma spokesman Kevin Harrison said the company estimated that about 10,000 customers remained without power at midday yesterday, down from the weekend peak of 25,000 to 30,000.

In central Oklahoma, a spokesman for Oklahoma Gas & Electric Co. said power was restored to all but "a few thousand" customers.

In the Mississippi Valley, rain that began Christmas Day ended after more than 14 inches fell at Millington, Tenn., where about 3,200 people were evacuated.

"The end is in sight," said Ed Werner of the weather service in Memphis.

Across the Mississippi River, about 450 people in West Memphis, Ark., had yet to return home, officials said.

Before the flood, that city was hit by a tornado Dec. 14 that killed six people and caused $35 million damage.