A storm is expected to dump snow on the state this weekend after heavy winds damaged power lines and trucks.

Travelers should prepare for dangerous driving conditions with “significant reductions in visibility at times” and weather-related damage to trees and power lines through the weekend, according to the National Weather Service (NWS), which issued a winter storm warning Friday morning. Drivers are urged to bring emergency supplies, including flashlights, blankets and food, and they could encounter slushy, snowy, icy road conditions.

Lows Saturday in the Salt Lake and Tooele valleys are expected to reach the mid-40s on Saturday. Heavy snow is expected to begin about 5 p.m. Saturday, with snow accumulations of 4 to 8 inches, the NWS said. Temperatures Saturday night are forecast to drop into the mid-20s, with a 100 percent chance of snow.

The NWS expected heavy snow to fall in the Wasatch Mountains and western Uinta Mountains, with accumulations of 12 to 20 inches. In Cache Valley, the northern Wasatch Front and Great Salt Lake Desert and mountains, the NWS predicted 6 to 12 inches, with up to 15 inches on the benches.

Areas in the Wasatch Mountain valleys, including Park City and Weber, are forecast to get 5 to 10 inches of snow.

A hazardous weather outlook warned that the strong winds and snow would continue moving across the state over the next few days, and a special weather statement from the NWS warned anyone in eastern Utah to expect warm and windy weather until Sunday, when the cold front drops temperatures 15 to 20 degrees and dumps heavy snow onto valley floors.

In the St. George area, rain will likely begin Saturday night as more clouds move in, and temperatures will drop from 60 degrees into the mid-30s.

The Utah Avalanche Center warned of considerable avalanche danger over the weekend.

On Friday, strong winds blew down power poles, toppled semis on the interstate and caused liquor stores to close early.

More than 4,700 Rocky Mountain Power customers along the Wasatch Front were without power Friday morning because of downed power lines, the company’s outage map showed.

Rocky Mountain Power spokeswoman Tiffany Erickson said extra crews — about 100 linemen — would be on standby during the upcoming snowstorm to help repair any lines damaged by the extreme weather.

Rocky Mountain Power urged customers to be prepared for severe weather by clearing off snow and ice from vehicles before driving; securing tarps, patio furniture and other objects that could become airborne in strong wind; driving slowly and at a safe distance; being aware of ice on bridges, ramps and overpasses; and never leaving space heaters unattended. Erickson also suggested having blankets, coats and other emergency supplies ready in case of outages.

Southbound winds blew from 30 to 40 mph, with gusts in excess of 60 mph, in the Salt Lake and Tooele valleys on Friday.

North Tooele Fire District reported about 9 a.m. Friday that three semis had blown over on Interstate 80 within the hour prior, and it cautioned drivers of tall vehicles to avoid the area. The Utah Department of Transportation closed I-80 to semis that have empty trailers from Wendover to Lake Point in Tooele County about 9:20 a.m.

The Utah Department of Alcoholic Beverage Control had announced that liquor stores in Logan, Harrisville, Layton and the Pacific Avenue location in Ogden would close early Friday due to the potential of severe weather.

All four stores, however, stayed open until their regularly scheduled closing time of 10 p.m.

FlightAware.com reported 163 delays and 15 cancellations into and out of the Salt Lake City airport on Friday, though the cause for the delays was not apparent.

For more detailed weather information, visit The Salt Lake Tribune’s weather page at www.sltrib.com/weather.