Atmospheric river brings flooding, landslides across California on New Year’s weekend

Rockslides and mudslides closed roads Friday across California as heavy rains kicked off a series of storms that will start the new year with rain and possible flooding across much of the state and several feet of snow in the Sierra Nevada.

The atmospheric river storm, a long and large plume of moisture that moved in from the Pacific Ocean, began sweeping the northern part of the state on Friday and was expected to bring more rain through Saturday, according to the National Weather Service in Sacramento.

A winter storm warning was in effect Sunday for the upper Sierra elevations from south of Yosemite National Park to north of Lake Tahoe, where up to 1.5 meters of mountaintop snow is possible, according to the National Weather Service. he said in Reno, Nevada.

A flood watch was in effect for much of Northern California until New Year’s Eve. Officials warned that rivers and streams could overflow and urged residents to pack sandbags.

Landslides had already closed routes in the San Francisco Bay Area, between Fremont and Sunol, as well as in Mendocino County near the unincorporated community of Piercy and the Mendocino National Forest, where crews cleared debris Friday night.

Humboldt County, where a magnitude 6.4 earthquake struck on Dec. 20, also saw roads flood, according to the National Weather Service’s Eureka office. A bridge that was temporarily closed last week due to earthquake damage may be closed again if the Heli River, which it crosses, rises too high, officials said.

Authorities in San Mateo County closed a section of Highway 92 in Half Moon Bay early Saturday morning as rainwater spread across the stretch amid continued heavy rain. They said there is no “estimated time to reopen.”

It was the first of several storms expected to hit California next week. The current system is expected to be warmer and wetter, while next week’s storms will be colder, reducing snowpack in the mountains, said Hannah Chandler-Cooley, a meteorologist at the National Weather Service in Sacramento.

The Sacramento area could receive a total of 4 to 5 inches (10 to 13 centimeters) of rain during the week, Chandler-Cooley said.

The California Highway Patrol reported some local roads in east Sacramento were underwater and impassable at times Friday. By evening, nearly 5 inches (12.7 centimeters) of rain had fallen in the past 24 hours in the Sierra foothills in Blue Canyon about 70 miles (112 kilometers) northeast of Sacramento, the weather service said.

Sacramento fire officials planned to broadcast evacuation notices from a helicopter and a boat along the American River – a spot where many displaced people live in encampments – to warn of flooding.

In a tweet, the California Highway Patrol highlighted a landslide in Alameda County that scattered timber across a road bend.

“A good reminder to slow down with all the rain we’ve had. You never know what’s around the next corner. Drive safe and give yourself extra time,” the service’s Dublin office tweeted on Friday.

A winter storm warning was in effect until 4 a.m. on Sunday for much of the Sierra, including the highest elevations around Lake Tahoe where more than a foot of snow was expected near shore at about 6,200 feet (1,889 meters) and up to 5 feet (1.5 meters) above 8,000 feet (2,438 meters) with winds blowing up to 100 mph (160 km/h) over peaks.

“Strong winds could damage trees and lead to power outages, and high waves in Lake Tahoe could capsize small boats,” the weather service in Reno said.

Avalanche warnings were issued for the backcountry around Lake Tahoe and Mammoth Lakes south of Yosemite.

On the eastern front of the Sierra, flash flood watches and warnings continue through the weekend north and south of Reno, Nevada, where minor to moderate flooding was expected along some rivers and streams through the weekend.

In Susanville, California, about 85 miles (137 kilometers) north of Reno, the Susan River was forecast to rise from about 5 feet (1.5 meters) on Friday to a foot (30 centimeters) above flood stage of 12 feet ( 3.6 meters) Saturday morning, causing moderate flooding that could affect some homes, roads and bridges, the National Weather Service said.

In Southern California, moderate to heavy rain was forecast for Saturday. The area will begin to dry out in the New Year, and the January 2nd Rose Parade in Pasadena should avoid the rain.

Heavy rain is forecast for Tuesday or Wednesday, the National Weather Service in Oxnard said.

The rain was welcome in drought-parched California, but much more rainfall is needed to make a significant difference. The past three years have been California’s driest on record.

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