Updated 6:24 p.m.
(AP) — A winter storm slamming the western U.S. was dumping rain in Northern California on Tuesday and raising the threat of floods while heavy mountain snowfall created a risk of avalanches and whiteout conditions on roads in the Sierra Nevada.
The National Weather Service issued flood warnings and flash flood watches for the San Francisco Bay Area and many parts of the Sacramento area into Thursday evening.
While some areas could see 6 inches of rain or more — and as much as 12 inches on mountains — the intensity will not be fierce enough to cause devastating mudslides in areas denuded by a string of devastating wildfires, such as Shasta and Lake counties, the weather service said.
Some small creeks and streams had flooded and the weather service warned that two rivers north of the San Francisco Bay Area were likely to overflow their banks by Wednesday morning. The weather service said that Cache Creek in Yolo County was forecast to reach flood stage Wednesday, possibly impacting parts of Woodland.
The storm has also prompted California authorities to order mandatory evacuations for two dozen small communities.
The order covers a 35-mile stretch of communities in Sonoma County along the Russian River, which was expected to overflow Tuesday night when it reaches 32 feet.
The town of Guerneville, population 4,500, was the largest ordered to evacuate.
The river was expected to crest Wednesday night at 46 feet in the community 80 miles west of Sacramento.
"We're definitely in high concern mode," said Sonoma County sheriff's Sgt. Spencer Crum. "We're bringing our boats out here and we're letting the public know to take this one serious."
Earlier Tuesday at the River Inn Grill in Guerneville, workers were preparing by putting perishables on high shelves in storage rooms.
But manager Andre Vazquez said the one-story building could be largely submerged that if the river reaches 46 feet.
"If it gets to 46 feet, it's done. There is no way to prepare for that," Vazquez said.
The town often floods during heavy rain and people seemed nonchalant Tuesday about the threat, said Joseph Chung, whose parents own the Koala's Fine Food restaurant.
"A couple of weeks ago people were using kayaks to get to their mailbox," Chung said. "If it gets really bad, we'll get out."
For now, Chung said, the restaurant planned to stay open until its normal 10 p.m. closing time.
In the Sierra Nevada along the California-Nevada line, forecasters warned of possible whiteout conditions from blowing snow in high mountain passes. The mountains could get up to 6 feet of snow at higher elevations and winds gusting to 140 mph over ridgetops.
Here’s more video from 80, this from Donner Summit about 20 minutes ago. 80 remains closed in both directions with no ETO. pic.twitter.com/IEyikWMLZf— Caltrans District 3 (@CaltransDist3) February 27, 2019
Several mountain highways, including Interstate 80 at Donner Summit, were repeatedly closed for short periods Tuesday because of whiteout conditions.
The storm already has barreled through other parts of the West, toppling trucks and trees, triggering power outages and closing roads and schools from Oregon to Montana.
It is the latest in a string that has dumped record levels of snow and rain this winter in the western U.S.