A slow-moving winter storm was intensifying over California on Friday, forecasters said, a day after walloping large swaths of the West with snow and a wintry mix that disrupted travel along a number of major roads.
Multiple rounds of heavy snow combined with strong winds will create blizzard conditions over high terrain and mountain passes, including in the Sierra Nevada and the Transverse Range in Southern California, the National Weather Service said early Friday.
While the winter weather began in some areas on Thursday, the greatest chances for rain, heavy snow and strong winds in the southern part of the state was on Friday. Several inches of rain may fall along the coasts and valleys, and the heaviest snow, up to seven feet, may fall in elevations 4,500 feet above sea level. Areas between 2,500 and 4,500 feet are expected to receive up to a foot of snow. Wind gusts of 60 to 75 miles per hour are expected throughout the day.
Early Friday, more than 116,000 customers in California, mostly in the northern part of the state, were without power, according to PowerOutage.us.
Millions of people in the West, mainly in California and Nevada, were under winter weather alerts, and the Weather Service issued a rare blizzard warning for the mountains of Los Angeles, Ventura, Santa Barbara and San Bernardino Counties until Saturday afternoon. Officials in Ventura County issued evacuation warnings for some inland communities, including around Ojai, through Saturday morning because of “anticipated flooding and debris flows.”
“This blizzard warning is something that our community is not used to hearing about,” said Jackie Ruiz, the public information officer for the Santa Barbara County Office of Emergency Management. She said the county’s message was simple: “If you don’t have to go out, stay home.”
As some Californians marveled at the unlikely white landscape, many were trying to put a name to what they were seeing: Was it rain, snow, sleet, hail or graupel? The National Weather Service offered a vocabulary lesson for wintry mix beginners. Hail, or frozen precipitation of ice from thunderstorms, is hard and solid; graupel, or snowflakes that collect supercooled water droplets, is soft and wet.
The storm snarled major transportation arteries, causing road closures, high wind warnings and advisories for drivers to use chains on their tires.
A stretch of Interstate 80 was closed because of zero visibility between Colfax, about 60 miles northeast of Sacramento, and the Nevada state line, a total distance of about 95 miles, according to the state Department of Transportation.
Parts of Interstate 5, a major north-south route that runs from the border with Mexico to Canada, were shut down in areas in Siskiyou and Shasta Counties in the northern part of the state. The Grapevine, a 40-mile stretch of I-5 from northern Los Angeles County to Kern County, was shut down on Friday morning, and the authorities said there was no estimated time for when it might reopen.
In Santa Cruz County, the authorities advised against travel because snow and ice were making it “extremely difficult” along multiple roads and at higher elevations in the Santa Cruz Mountains.
On Thursday, the storm paralyzed parts of Oregon, trapping motorists for hours while others abandoned their vehicles on the side of the road. Travel disruptions persisted early Friday, with the Oregon Department of Transportation announcing closures along at least three highways. On Wednesday, the storm produced 10.8 inches of snow in Portland, giving the city its second-snowiest day on record, forecasters there tweeted. Many colleges, universities and school districts remained closed on Friday.
Farther east, snowfall also caused dangerous road conditions in Wyoming, leading to road closures along the southern portion of the state.
The West Coast can be one of the hardest places in the country to predict weather because of the lack of observations over the Pacific Ocean, and the intensity of the storm caught many people — including forecasters — by surprise.
Mark Pestrella, the director of the Department of Public Works for Los Angeles County, said officials were urging residents in the northern parts of the county to shelter in place beginning on Friday because of expected widespread road closures over the weekend and to “be ready for basically a snow day” that, while being rare and exciting, could still pose a danger.
“It’s not a weekend for the beach,” he said. “What we’re really recommending is everybody hang tight and let us get the snowfall, and then after that, we can get out.”
“Everything is adding up for a major snow event,” said Andrew Rorke, a senior forecaster for the Weather Service office in Los Angeles.
A person standing in downtown Los Angeles can see a 10,600-foot peak that will typically have snow on it, Mr. Rorke said. By Saturday, that snow will extend much farther down the mountain, showing more snow than a typical winter storm.
Though the Hollywood sign was not likely to be lost in a snow-covered hillside, snow or graupel was seen falling Thursday morning near the sign, the Weather Service Office in Los Angeles confirmed.
In the Sierra Nevada, the snowpack was already above average for this time of the year, and more snow is in the forecast. Even though snow is nothing new for this region, forecasters in Reno, Nev., were calling it a major storm that will disrupt travel.
“While we cannot definitively say there will be road closures, nor do we have any control over this, past events have certainly brought similar impacts,” the forecasters said.
There is also a high risk for avalanches across the Sierra Nevada on Friday, according to the Avalanche Forecast Center.
This will not be the last winter storm to hit the area; forecasters from all Weather Service offices in California are predicting another storm at the beginning of next week.
