OMAHA, Neb. (AP) -- Inclement weather plagued areas of the U.S. in the first half of the weekend, with dangerous conditions including heavy snow in upstate New York, a major ice storm in Midwest states, severe weather warnings around Lake Tahoe and unsual tornado activity in Central California.

The ice storm beginning Friday evening created treacherous driving conditions across Iowa and eastern Nebraska Friday and into Saturday and prompted temporary closures of Interstate 80 after numerous cars and trucks slid off the road. In upstate New York, more than 84 centimeters was reported near Orchard Park, which is often a landing point for lake-effect snow.

On Saturday, a tornado touched down near a shopping mall in Scotts Valley, California, about 110 kilometers south of San Francisco, around 1:40 p.m. The tornado overturned cars and toppled trees and utility poles, the National Weather Service said. The Scotts Valley Police Department said several people were injured and taken to hospitals.

Some trees toppled onto cars and streets and damaged roofs in San Francisco. The damage was being assessed to determine if the city was indeed hit by a tornado, which had not occurred since 2005, according to the weather service.

Roger Gass, a meteorologist in the weather service's office in Monterey, California, said the warning of a possible tornado in San Francisco was a first for the city, noting an advanced alert did not go out before the last tornado struck nearly 20 years ago.

"I would guess there wasn't a clear signature on radar for a warning in 2005," said Gass, who was not there at the time.

The fast-moving storm prompted warnings for residents to take shelter, but few people have basements in the area.

"The biggest thing that we tell people in the city is to put as many walls between you and the outside as possible," Meteorologist Dalton Behringer said.

More than 30 centimeters of snow fell at some Lake Tahoe ski resorts, and a 181-kph gust of wind was recorded at the Mammoth Mountain resort south of Yosemite National Park, according to the weather service's office in Reno, Nevada. Up to 91 centimeters of snow was forecast for Sierra Nevada mountaintops.

The Tahoe Live music festival at Palisades Tahoe ski resort in California was expected to go ahead as planned Saturday and Sunday in spite of a winter storm warning for the area. Lil Wayne was scheduled to perform Saturday night, with Diplo as the headliner on Sunday, the festival's website said.

A winter storm warning was set to expire at 10 p.m. Saturday, but an avalanche warning remained in effect into the following night for elevations above about 2,400 meters around Tahoe.

Interstate 80 was closed along a 130-kilometer stretch from Applegate, California, to the Nevada line just west of Reno on Saturday. The California Highway Patrol reopened the road in the afternoon for passenger vehicles with chains or four-wheel drive and snow tires.

The severe weather in the Midwest resulted in at least one death. The Washington County Sheriff's office in Nebraska said a 57-year-old woman died after she lost control of her pickup on Highway 30 near Arlington and hit an oncoming truck. The other driver sustained minor injuries.

Businesses announced plans to open late Saturday as temperatures rose high enough in the afternoon to melt the ice in most places.

"Luckily some warmer air is moving in behind this to make it temporary," said Dave Cousins, a meteorologist with the National Weather Service's office in Davenport, Iowa.

Tens of thousands of people in western Washington state lost electricity Saturday as the system delivered rain and gusty winds, local news outlets reported.