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Storms are making a dent in California’s drought; 7 feet of snow expected in some areas

Hundreds of people were evacuated from their homes as rivers overflowed their banks.

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The third and latest storm to hit the state within a week is expected to inundate rivers in Northern California and flood parts of Napa Valley wine country, while also blanketing the frigid Sierra Nevada in heavy snowfall, according to state officials.

The storm, which is expected to last through Thursday, could dump up to 7 feet of snow across the Sierra, greatly bolstering the state’s snow-water supply. Mountain snowpack on Tuesday measured 135% of the seasonal average, according to the California Department of Water Resources.

On Monday, it was at 126% of its average for this time of year.

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A few big storms alone won’t end California’s six-year drought. However, the appearance this year of a “Pineapple Express” — a type of atmospheric river originating in the tropics — is making a welcome dent in California’s water deficit.

Officials released water from the Folsom Lake reservoir and several others as a flood-control measure Monday.

For the first time in 11 years, the floodgates of the Sacramento River also were opened, releasing a wall of water downstream into the Yolo Bypass, one of several drainage areas designed to catch floodwater. The National Weather Service warned farmers in that region to move farming equipment and livestock out of the way.

The impending storm is expected to usher in several feet of snow in higher elevations and inches of rain in the foothills and valleys. By the end of the week, the total for the year could already be up to 20 feet. That means a generous addition to the Sierra Nevada snowpack, a precious water supply that California cities and farms rely on when it melts in the spring and summer.

Whiteout conditions caused by blowing snow on U.S. 395 near Convict Lake, Calif., Monday afternoon. (Brian van der Brug / Los Angeles Times)

“We haven’t seen an event of this magnitude in at least a decade,” state climatologist Mike Anderson said.

The storms over the weekend were relatively warm, meaning snow fell only at high elevations. Some of that snow melted fairly quickly, creating raging rivers — and flooding — across the region.

But the latest storm will be colder, allowing more of the snow to stick. That’s good news for the state’s water-collection system, which relies on snow remaining in the Sierra Nevada into the spring.

The colder storms bring with them the threat of blizzard and whiteout conditions, as well as avalanches. The NWS issued a blizzard warning Tuesday, and heavy snow closed Interstate 80 and U.S. 395.

Forecasters warned of wind gusts topping 150 mph, drifting snow and zero visibility at high elevations.

There also were fears of more flooding, with new warnings issued for the Napa and Russian rivers.

“It’s not over yet,” said Alex Hoon, a meteorologist in the National Weather Service’s Reno station.

Many Northern California communities are still reeling from rainfall that left tens of thousands of households without power, cut off main transportation arteries, stranded motorists and felled trees, including a giant sequoia that served as a tunnel in Calaveras County.

Residents along the Napa River in St. Helena have been warned the river could flood by Tuesday afternoon, washing out crops and eroding land.

In the Sacramento Valley, rain and melting snow continue to fill the Sacramento river, and forecasters warn that the waterway will flood a county park by Tuesday afternoon. Water levels are expected to begin receding by early Wednesday.

The risk and timing of flooding along state rivers is a matter of topography.

A relatively narrow waterway like the Russian River, which snakes between steep mountains and hillsides that shed rainfall quickly, poses a greater risk of immediate flooding, according to Anderson, the state climatologist. Forecasters anticipate that the Russian River likely will flood again Wednesday, affecting hundreds of residents in Guerneville.

The Sacramento River, however — which is bigger and draws water from forests up to 100 miles away — rises more slowly in times of heavy rain.

“It takes three days for water from Shasta to get down to Sacramento,” Anderson said. “So even after we get past the storm, we want to manage the flood space because it’s going to take a few days for it to get through the system.”

Workers have been monitoring the state’s rivers around the clock since the weekend and will continue to do so until possibly Friday, said Doug Carlson, a spokesman for the state Department of Water Resources.

“We’re not going to take our foot off the pedal here,” he said.

The Union Pacific Railroad at Norden was washed out by rain Sunday night, cutting off Amtrak passenger and freight trains into and out of California. A Union Pacific spokesman said the railroad expected to have the line reopened by Monday evening.

Interstate 80 reopened Monday morning heading east, but westbound drivers attempting to enter California were stopped at the border. Those who could show they had business in Truckee were allowed through, but for the rest, the remnants of a giant mudslide from Sunday evening kept the road closed.

Heavy-machinery operators had made progress overnight, said California Highway Patrol Officer Peter Mann, but water cascading off the Donner Summit slope was the next problem.

“We have a river on the interstate,” Mann said.

Other key highways including Interstate 280, U.S. 395 and U.S. 101 were closed for periods because of hazardous conditions, such as mudslides.

Residents in the ski town of Mammoth Lakes spent the weekend rushing to fill sandbags to protect their homes amid gusty winds, thunder and lightning. Still, the slush that filled their streets seeped into their homes and garages.

Sonoma County officials issued voluntary evacuation orders to hundreds of households near swollen rivers. Picnic tables on campgrounds were submerged after the Truckee River overflowed.

Ten homes in the Carmel Valley were flooded late Sunday after a river swelled from the heavy rain, authorities said.

In Nevada, Gov. Brian Sandoval declared a state of emergency.

Yosemite National Park closed the popular Yosemite Valley because of flooding worries over the weekend, but reopened it Tuesday.

The Merced River in Yosemite Valley reached flood stage at Pohono Bridge on Sunday. The river peaked at 12.7 feet at 4 a.m. The park is assessing the impacts and will address any repair needs in the coming days and weeks. Although there was no major flooding in Yosemite Valley, its roads and sewer systems were affected.

Authorities were trying to determine whether the deaths of three people in the Bay Area — one killed by a falling tree, the other two by car accidents — were related to the storm.

In Southern California, more wet weather is on the way. A pair of storms predicted to move through the region throughout the week will bring moderate rains Tuesday and Wednesday, according to the National Weather Service, while a much colder storm Thursday and Friday could drop snow levels as low as 4,000 feet.

Rain will spread over Ventura and Los Angeles counties, the weather service said, followed by light showers through Wednesday night. That storm could bring 1/4 to 3/4 inches of rain. Snow levels could drop to 3,500 feet or lower Thursday afternoon, resulting in winter driving conditions in mountain areas. Snow and slick roadways may jam the commute in mountain passes, including Interstate 5 through the Grapevine. Rain and snow showers will continue in Ventura and Los Angeles counties through Friday afternoon.

Forecasters said this week’s earlier storm dropped .77 inches of rain in downtown Los Angeles, bringing the rain total to 7.21 inches since Oct. 1. The 30-year average during this time of year is 4.95 inches, said Jayme Laber, a hydrologist for the National Weather Service in Oxnard.

“We’re above average for this time of year in downtown L.A.,” Laber said. “That’s a good thing, considering we’ve had 5 years of drought.”

paige.stjohn@latimes.com

louis.sahagun@latimes.com

joseph.serna@latimes.com

corina.knoll@latimes.com

St. John reported from Truckee, Sahagun from Mammoth Lakes, and Knoll and Serna from Los Angeles. Times staff writers Matt Hamilton, Sarah Parvini and Veronica Rocha contributed to this report.

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UPDATES:

1:20 p.m.: This article was updated with Napa Valley flooding forecasts and predictions of intense wind gusts.

11:50 a.m.: This article was updated with river flooding forecasts.

8:44 a.m.: This article was updated with a revised forecast.

7:30 a.m.: This article was updated to add a blizzard warning.

This article was originally published at 5 a.m.


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