A heavy winter storm hit northwestern Utah valleys and the northern mountains early Tuesday, causing dozens of accidents as vehicles slid off snowpacked, icy freeways.

The problem of vehicles sliding off roadways appeared to be most acute on freeways on the east and southeast sections of the Salt Lake Valley.The Utah Highway Patrol handled about 30 accidents alone between about 7 and 9 a.m. Most were on I-80 near Parleys Canyon, northbound and southbound lanes of I-215 on the east side of the Salt Lake Valley and the collector system southbound to 2100 South. Conditions on I-15 were reportedly not too bad. Two minor injury accidents had been reported by 9:30 a.m., a patrol dispatcher said.

Numerous small accidents were reported by Davis County law enforcement agencies Tuesday morning, but they were limited to fender benders and vehicles sliding off slick roads.

The storm dumped a mixture of rain and snow on the roads during the morning commute time, slowing traffic but not causing any major problems, dispatchers reported early Tuesday.

Farther south, a Utah Highway Patrol dispatcher said, "There have been so many accidents we are going nuts. (Fortunately) most of the accidents have just involved property damage. (Troopers) have handled or had reports of dozens and dozens of accidents throughout the Salt Lake Valley. That is a gross understatement of the problem," Utah Highway Patrol dispatchers said at 10 a.m.

Eastbound and westbound lanes of I-80 through Parleys Canyon were open at 10 a.m., but the highway was snowpacked and extremely slick.

Roads and freeways on the east and west sides of the valley were in bad condition, but those on the east seemed to be worse for travel because of wind near the canyons, a dispatcher said.

In posting a winter storm warning for the northwestern Utah valleys and northern mountains, National Weather Service meteorologists Ed Carle and William J. Alder said snowfall was expected to increase over all of northern Utah by Tuesday afternoon, continuing into the evening. Snowfall will be heavy at times. Wasatch Front valleys can expect an additional 4 to 6 inches with up to 2 feet more snow in the mountains by Wednesday morning.

The storm system is expected to move into the southern part of the state Tuesday night and Wednesday with areas of snow.

The Weather Service urged motorists to avoid travel through Utah Tuesday evening.

"The evening commute in the metropolitan area will be real slow and hazardous. Slow down. Drive defensively and allow plenty of space between you and vehicle you are following," the meteorologists advised.

In addition to hazardous conditions on the highways, extreme avalanche danger exists in the Wasatch Mountains from Spanish Fork Canyon to the Ogden area.

The highway in Little Cottonwood Canyon was closed early Tuesday and Utah Department of Transportation crews were still working at 11:15 a.m. to remove snow from the highway, where several slides crossed the road, said Tom Kimbrough, forecaster at the Utah Avalanche Forecast Center.

Eight inches of snow fell between 5 a.m. and 10 a.m. in the canyon, Kimbrough said.

Slides roared down some Little Cottonwood Canyon slopes Monday. No slides hit the road that day, but they came close.

Alder said the "mountains, especially Big and Little Cottonwood canyons, have been getting clobbered with high density wet snow. That's the kind of snow you have to worry about, especially when you get a lot. It's like cement. The snow at Alta lifts had 3.15 inches of water from Saturday night until 4 a.m. Tuesday. That's a lot of water, but we need it," Alder said.

Kimbrough said the avalanche warning was in effect for all slopes steeper than 30 degrees and above 6,000 feet. Spontaneous avalanches are likely, Kimbrough said.

He said backcountry travel is not recommended. The advisory does not apply to developed highways or ski areas where control work is normally done. For more details call your local number to receive recorded avalanche information. In the Salt Lake area, call 364-1581; in Park City, 649-2250; in Logan, 752-4146; in Ogden, 621-2362; and in Provo, 374-9770.