LOS ANGELES (AP) - Southern Californians looked forward to a day of expected clear skies and open roads Thursday after a pre-winter storm dumped snow and rain on much of the state, shutting down major highways and leading to accidents involving horses, helicopters and countless cars.

Sunny skies and rising temperatures were expected in most of Southern California, but freezing temperatures were likely to persist and even worsen to the north.

An overflowing river on the U.S.-Mexico border Wednesday led to the evacuation of nearly two dozen people and rescues of about 50 horses.

In Nevada, a rare snowfall blanketed Las Vegas, canceling all flights in and out of the city, snarling traffic and dusting palm trees and marquees along the Las Vegas Strip with accumulations that were expected to reach 3 inches overnight.

Other locations were forecast to receive as much as 8 inches of snow in the second winter storm this week to drop snow on the desert city.

Snow piled up around the famous "Welcome to Fabulous Las Vegas" sign on the south end of the Strip, as visitors parked and posed for pictures wearing hooded jackets.

Snow also fell across much of Washington state on Wednesday, with Spokane, in the northeast part of the state, declaring a snow emergency and vowing that its snowplows would be working nonstop until the streets were clear.

Most areas of Spokane had picked up 8 inches of snow by evening, with another 5-10 inches expected by daybreak Thursday, said National Weather Service meteorologist Jeffrey Cote.

Frustrating thousands of commuters and travelers, snow shut Interstate 15 over 4,190-foot Cajon Pass east of Los Angeles and roads through the San Gabriel Mountains connecting metropolitan Los Angeles to the commuter suburbs of Palmdale and Lancaster in the high desert to the north.

Interstate 5, a major trucking and travel route connecting Southern California with the Central Valley and Northern California was shut down over 4,144-foot Tejon Pass.

Massive backups developed below all the passes, which authorities hope to have reopened sometime after sunrise Thursday.

The storm dumped as much as 4 feet of snow at Big Bear in the San Bernardino Mountains, said James Oh, a forecaster with the National Weather Service in San Diego.

Calen Weiss, 19, of Tarzana, his brother and two friends wanted to go snowboarding at Big Bear but instead got stuck on I-15 in Cajon Pass for an hour as visibility fell to about 40 yards.

"It looks like Whoville, all snowy, but with less joy and more extreme misery," he said by phone from the Summit Inn.

Heavy rain also fell in some parts of Southern California through the day.

Near the California-Mexico border, San Diego firefighters and lifeguards evacuated 21 people along the overflowing Tijuana River, said spokesman Maurice Luque. They included 12 to 15 people who were on high ground outside a home, surrounded by up to 4 feet of water.

Five people were taken out by helicopter, while others were escorted in Border Patrol all-terrain vehicles, Luque said. Three men were taken to a hospital for treatment of hypothermia.

About 50 horses also were evacuated, but three others drowned and one was euthanized after tripping on barbed wire, Luque said.

In the Santa Clarita area north of Los Angeles, a wind gust caused a helicopter to crash, killing an electrical worker on the ground and leaving the pilot with minor injuries, county fire Inspector Frank Garrido said.

Even Malibu got a dusting of snow, as the usually balmy city saw a half-inch in the afternoon.

"It's a combination of snow and rain, so none of the snow is sticking on the ground," said Craig Levy, director of a juvenile detention camp near Mulholland Highway. "It's kind of cool if you think about it. It's kind of unusual to see snow in Malibu."