LOS ANGELES -- Deputies went door-to-door ordering residents to evacuate from coastal Southern California neighborhoods ahead of a powerful winter storm sweeping in Friday after bringing heavy snow and whiteout conditions to northern mountains and steady rain elsewhere.
As many as 30,000 people were under evacuation orders in foothills of Santa Barbara County, which were stripped bare by recent wildfires.
Sheriff Bill Brown said forecasters weren't certain how intense the storm would be, but modeling indicates "there is risk to life and property and risk of disruption to critical services," he warned.
"I'm not going anywhere," said Harriet Mosson from her home in Montecito, the wealthy enclave devastated by deadly mud and debris flows during downpours Jan. 9.
The 76-year-old said the three-story condo where she lives was not damaged then because it's on the oceanside of U.S. 101, which helped divert the mudslides that roared down the mountains.
"Can it happen again? Yeah, I guess it can. Will it, now? I'd doubt it," she said. "And if something terrible happens, I'll be able to get out of here."
Ride-hailing companies Uber and Lyft were offering free rides for residents to local shelters. Authorities didn't know how many people were heeding the orders to get out. People cannot be forced to leave their homes under a mandatory evacuation order, but authorities said they should not be expected to be rescued while the storm event is occurring.
To the north, a blizzard warning was in effect for parts of the Sierra Nevada, where winds could gust up to 125 mph on ridges and 60 mph in some valleys, the National Weather Service said.
The cold front was expected to bring snow to foothill areas as low as 3,500 feet, and officials warned people to stay off mountain roads.
The California Department of Transportation said a 90-mile stretch of Interstate 80 was closed between Colfax, California, and the Nevada state line due to whiteout conditions.
Chains or snow tires were needed on stretches of Interstate 80, U.S. 50 and U.S. 395. Dozens of collisions were reported on San Francisco Bay Area highways.
As much as 6 feet of new snow was possible in the upper elevations of the Sierra around Tahoe, where more than a foot fell Thursday, says CBS News weather producer David Parkinhson. Authorities also warned of high avalanche danger for the backcountry.
The snow will help the Sierra snowpack, which is vital to the state's water supply and is only about a quarter of its normal depth for this time of winter.
Stephanie Myers, a spokeswoman for Heavenly Mountain Resort and Kirkwood Mountain Resort in Lake Tahoe, estimated snow was falling at about 2 inches an hour.
"We're thrilled about this storm," Myers said. "Once the storm moves out of the area, we'll have a beautiful bluebird powder day."
Predictions of widespread showers raised concern about flash flooding in Southern California. The rain totals won't be like the last big storm, but will be enough to potentially cause more slides, says Parkinson. "We're looking at an inch or a little more in just a few hours" Friday morning, he adds.
Santa Barbara County ordered the immediate evacuations for residents of areas burned by three major wildfires over the past 18 months.
The order encompasses Montecito, where a Jan. 9 storm triggered flash floods that destroyed or damaged hundreds of homes. Twenty-one people were killed and two remain missing. Other areas impacted by the order are Goleta, Santa Barbara, Montecito, Summerland and Carpinteria.
The county is following a rigorous new system of alerts that emphasizes evacuations well in advance of storms rather than suggesting residents can use their discretion.
Brown said evacuations in wildfire burn areas will be part of "the new normal" following the devastation in Montecito.