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.
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.
“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.
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.”