Boosting what has been a mediocre start so far to the winter season, a storm from the Pacific Northwest is expected to bring widespread rain to the Bay Area on Thursday and blanket the Sierra Nevada with up to 3 feet of new snow.
"This is a pretty good event. It's going to be beneficial across the board," said Brayden Murdock, a meteorologist with the National Weather Service in Monterey. "We are excited for this one."
The National Weather Service has issued a winter storm watch for the Sierra Nevada from Wednesday night through Thursday night, warning of poor visibility due to blowing snow and high winds at higher elevations. Snow levels should range from 3,500 to 5,000 feet.
The storm system would be the first significant rain or snow in Northern California in more than three weeks, and comes as the state is entering its fourth year of drought. A hoped-for storm fizzled last week, but this one is on track, forecasters say.
Cities around the Bay, including San Jose, San Francisco and Oakland, should receive about 1 inch of rain on Thursday as the storm moves in from the north, Murdock said. Coastal mountains in the North Bay, Santa Cruz area and Big Sur are expected to receive as much as 2 inches.
The rain could make the Thursday commute a challenge, with minor flooding in some areas if drainage systems become blocked with leaves and other debris.
If the rain lingers Thursday night into Friday morning as temperatures drop, there is an outside chance of light snow on higher Bay Area peaks, particularly Mount Hamilton in the Diablo Range, he added. Saturday has another, although lesser, chance of rain as well, forecasters said.
Most ski resorts in the Lake Tahoe area have opened in recent days, although with a large amount of machine-made snow. The storm Thursday will add a significant boost.
Conditions are expected to be so intense in some places that the U.S. Forest Service issued an avalanche warning Tuesday for back country areas Thursday in the Sierra Nevada between Yuba Pass (Highway 49) in the north and Ebbetts Pass (Highway 4) in the south, including the greater Lake Tahoe area.
California desperately needs a sustained pattern of rain and snow this winter. The last three years have been the driest three-year period statewide since records began in the 1800s.
On Tuesday, the Northern Sierra Index, a collection of eight weather stations in the watersheds that feed key reservoirs like Shasta and Oroville, was at just 53% of normal precipitation since Oct. 1. The last significant rain and snow in Northern California came on Nov. 8, when San Francisco received .89 inches and the Sierra Nevada received about 2 feet.
Currently, 85% of California is in a severe drought, with 40% in extreme drought, and 13% — mostly the San Joaquin Valley — in an exceptional drought, the worst of five categories, according to the U.S. Drought Monitor, a weekly federal report.
The drought has led to water restrictions in cities across California, and significant economic hardship for farmers.
A report last Tuesday from UC Merced found that the amount of irrigated farmland in California fell by 752,000 acres between 2019 and 2022, a drop of 9.9%. As a result, crop revenues to farmers decreased $1.7 billion, or 4.6%, this year. And food processing businesses saw a decline of $3.47 billion, or 7.8%.
Overall, the drought has cost an estimated 12,000 farm jobs in California, a 2.8% decline since 2019, with another 7,370 jobs lost in food processing, UC researchers concluded.
Farms across the Central Valley, like cities, have seen big drops in the amount of water they receive from state and federal projects as reservoir levels have fallen. Farmers have had to pump more groundwater, and have been restricted from taking as much water from streams and rivers as in past years.
The hardest-hit areas so far have been in the Sacramento Valley, particularly Sutter, Colusa and Glenn counties, where rice is a major crop.
"California is no stranger to drought," said Professor John Abatzoglou, a coauthor on the report. "But this current drought has hit really hard in some of the typically water-rich parts of the state that are essential for the broader state water supply."
On Tuesday, California's largest reservoir, Shasta Lake, near Redding, was 31% full. The second largest, Oroville, in Butte County, was 27% full. Similarly, Folsom Reservoir and San Luis Reservoir, east of Gilroy, were both 25% full.
Thursday's storm could bring most Northern California cities closer to their seasonal rain averages. But many more will be needed to break the drought and refill the reservoirs.
Jan Null, a meteorologist with Golden Gate Weather Services in Half Moon Bay, said that low rainfall totals in the early part of the winter season — October and November — historically haven't guaranteed an overall dry winter. Nor have wet Octobers and Novembers meant an overall wet winter.
Last year, October saw several huge storms, but then November was dry. December saw more storms, but January, February and March were record dry.
The most important months this year will be December, January and February, which typically account for more than 50% of Northern California's annual precipitation, he said.
"Those are the months that have to be big to make a difference in the drought," Null said. "Nobody has a crystal ball to know how those will turn out."
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