An avalanche in Little Cottonwood Canyon trapped two cars and a UTA bus and stymied traffic in three counties as a major winter storm rolled across the Wasatch Front Friday morning.

An avalanche also blocked traffic in Provo Canyon, and a number of other highways and canyons in northern Utah were also closed because of hazardous road conditions caused by heavy snowfall.The Utah Transit Authority bus was carrying 13 passengers out of Little Cottonwood Canyon when an avalanche crossed the road and caught the bus and two passenger cars.

UTA Marketing Director Ray Miller said a shaken bus operator radioed the UTA dispatch center at 8:40 a.m., saying he had been caught in the avalanche.

"He was stuck, but fortunately was just involved in the fringe, we did not get caught in the main part of the avalanche," Miller said.

There were no injuries.

Canyon patrol members were able to reach the occupants of the two cars and the bus and drive them to Snowbird, a Salt Lake County sheriff's dispatcher said.

Miller said it is likely more passengers would have been involved if the bus had been trapped while driving up the canyon instead of coming down. The bus was abandoned and will be retrieved after the avalanche is plowed clear of the road.

Skiers and other visitors to the canyon were trapped by the avalanche. Paula McKinney, a secretary at Alta Ski Resort, said the resort was closed until avalanche control measures could be taken, so visitors in the canyon would have to wait out the storm before they could ski.

By 10:30 a.m. eastbound I-80 had been closed and was reopened at 11:15 a.m. to four-wheel drive vehicles and cars with chains. Also closed during the morning hours were Little Cottonwood canyons, where there were multiple avalanches; Big Cottonwood Canyon; and Provo Canyon, where an avalanche occurred near Deer Creek Reservoir. Provo Canyon later reopened.

Utah Department of Transportation spokesman Kim Morris said I-84 was closed Friday morning between the Utah line and Burley, Idaho. U-143 was blocked to traffic near Panguitch.

Salt Lake area police dispatchers said they were surprised that the slick roads didn't cause more traffic accidents during the morning commute. That was partly due, they theorized, to the fact that many people took the day off Friday.

Most of Utah was blanketed with a new layer of snow. The St. George area, which rarely receives snow, received a light skiff for the second consecutive day, said William J. Alder, meteorologist in charge of the Salt Lake office of the National Weather Service.

"It's white, white everywhere. Santa's going to have good sleighing weather for the big day," Alder said.

The Highway Patrol was giving updates through the morning about requirements for chains on vehicles in Parleys Canyon.

Two avalanches roared down slopes in Weber County Thursday, and Bruce Tremper, director of the Utah Avalanche Forecast Center warned skiers and others to be alert, especially in the back country.

Trempor said there is an avalanche warning in effect for all of northern Utah.

"Things are pretty dangerous out there. We have had spontaneous avalanches reported on slopes facing almost every direction from 7,000 to 10,000 feet. We have had an avalanche warning still in effect for today in the northern Wasatch Mountains," Tremper said.

"If they don't have good snow stability and route-finding skills they should avoid the back country. Go skiing at a ski area where avalanche control" is practiced, Tremper said.

"It's OK to go into those areas if you have avalanche skills and as long as you know what you're doing," Tremper said.

Near blizzard conditions were reported in the Salt Lake Valley, particularly on the west side. Alder said wind gusts of 37 mph were clocked at the airport about 7:15 a.m. The wind died down a bit about 10 a.m.

New snowfall amounts generally ranged from 2 to 4 inches in valleys along the Wasatch Front to 5 to 7 inches on the benches. There was about a foot of new snow on U.S. 89 east of Kanab.

Six inches of snow fell in the community of Kanab, with 7 at the Highway Patrol checking station about 10 miles north of town.

Other snowfall amounts: Panguitch; 1 inch; Richfield, 2 inches; Olympus Cove, 5 to 6 inches; Provo, 2 to 3 inches; 5 to 7 inches in Hobble Creek Canyon, Utah County; Hooper, Weber County, 3; Cache Valley, a half inch to an inch of snow; Richfield, 2; Cedar City, an inch.

Alder said a winter storm warning was posted for all mountains through Friday night. "We should end up with 1 to 3 feet at some resorts from the storm that started Thursday night," Alder said.

Snow will begin falling again in the mountains late Saturday afternoon and in the valleys by sunset.

That storm will continue at least intermittently into Monday, Alder said.