Southland Catches Cold as Front Rumbles In : Weather: The strongest storm of the season may dump half an inch of rain on the Los Angeles Basin. It’s so cold it might even snow at the beach.

Arctic air advanced on Southern California in a powerful front Wednesday, raising prospects of much-needed rain in the lowlands, welcome snow in the mountains, and winter-like temperatures that could even bring a bit of the white stuff to the beach, a forecaster said.

As the chilly storm packing strong winds moved south, the National Weather Service warned motorists of blizzard conditions on Interstate 5 over the Tehachapis, where snow began falling Wednesday night, and issued winter storm warnings for the southern Sierra Nevada.

The storm had already shown its force to the north, dumping several inches of snow at sea level in Seattle and up to two feet at higher elevations at Lake Tahoe and other northern Sierra areas.

A blizzard warning was issued along the eastern slopes of the central Sierra.

Powerful winds raked the resort community of Mammoth Lakes north of Bishop, blowing snow and downing trees. Local forecaster Howard Schecter said Wednesday evening that six to 18 inches of snow had fallen in the village and up to two feet of snow had fallen at higher elevations on Mammoth Mountain.

Gale-force gusts whipped up a blinding sandstorm on Interstate 15 about 10 miles north of Barstow late Wednesday morning, triggering a chain-reaction collision involving a Greyhound bus, a big-rig truck and several automobiles, the California Highway Patrol said.

CHP Sgt. Gary Ross said two people on the bus suffered major injuries, eight or nine passengers suffered “moderate” injuries, including broken bones, and 20 to 25 others had cuts and sprains.

The accident happened when a semi-truck and trailer loaded with rolls of newsprint rear-ended a car that had slowed or stopped on the highway, Ross said. Then, the sergeant said, a Greyhound bus--a gambler’s special headed for Las Vegas--clipped the big-rig’s trailer and seven other vehicles smashed into the bus or truck or one another.

“It was a real bad sandstorm,” Ross said. “It was zero visibility.”

After the accident, a 57-mile section of the busy interstate, the main route between Los Angeles and Las Vegas, was closed for a time because of impaired visibility.

Strong winds boiled up dust and sand that hung over downtown Palm Springs “like a fog bank,” Police Lt. Dennis Heazlett said Wednesday night. Many trees were blown down and traffic signals were knocked out, he said.

“The storm is by far the strongest of the fall,” said Meteorologist Marty McKewon of WeatherData Inc., which provides forecasts for The Times.

McKewon expected the storm to dump up to an inch of rain on Southern California coastal mountain ranges and from a quarter of an inch to half an inch in the Los Angeles Basin before a break in the weather Friday and Saturday. He said more showers are possible Monday and Christmas Day.

Any amount of rain would be welcome in Southern California. Only 0.21 of an inch has been recorded at the Los Angeles Civic Center since the beginning of the rainy season, compared to 1.07 inches last year at the same time and a normal rainfall of 3.53 inches.

Along with the wet weather, McKewon predicted that it will be quite cool today in the Los Angeles Basin, with highs reaching only into the low 50s and dropping into the 40s Friday.

“It appears that Friday night will be the coolest night, with freezing temperatures possible in the Los Angeles Metropolitan area,” he said. “The snow level probably is going to lower to 1,500 feet in the San Gabriel and San Bernardino mountains.”

Because of the cold, McKewon predicted the possibility of snow showers in the metropolitan Los Angeles area.

“It could snow at Malibu,” he said.

On Wednesday morning, moist, unstable air in advance of the cold front brought showers, stiff winds, a dusting of snow in the mountains, and scattered power outages to the Southland as far south as San Diego.

Rainfall was minimal, with the largest amount, 0.08 of an inch, reported in Beaumont in Riverside County. El Toro and San Juan Capistrano in Orange County had 0.06. Lancaster in the high desert and Newport Beach in Orange County both registered 0.02.

Electrical outages were reported from Point Loma to Escondido, but power was restored to most areas immediately, San Diego Gas & Electric Co. reported.

The Los Angeles Department of Water and Power estimated that 2,500 customers were without power from 10 minutes to two hours Wednesday because of downed power lines.

In Ventura County, the cold and wind affected everyone from the homeless to farmers.

The National Guard Armory was scheduled to open its doors to the homeless for the seventh straight night Wednesday. Farmers, meanwhile, were using wind machines in an attempt to keep their citrus and avocado crops from freezing.

Shelters in the Los Angeles area were also open for the homeless.

Southern California Edison Co. reported several brief power outages caused by high winds in Ojai and Thousand Oaks.

In Orange County, the owners of the county’s $132-million nursery industry and $36-million strawberry crop braced for potentially devastating temperature drops forecast to dip below 30 degrees by Friday night.

“We have about 160 wind machines and two helicopters on standby for frost protection,” said Alan Reynolds, orchard manager for Treasure Farms, the county’s largest farming operation. “We could have some real problems by Friday if temperatures drop to the mid-20s.”