Atmospheric river headed to Bay Area, may bring light rain to Los Angeles by the weekend

More rain is on its way to California this week, continuing the state’s late-season run of storms, the National Weather Service said.

Starting Thursday, forecasters said, an atmospheric river swollen with subtropical moisture will arrive in the Bay Area, where it could dump up to 6 inches of rain in the coastal mountains before it flows south toward Los Angeles.

It’s due to arrive in Southern California by Friday night and could produce up to a third of an inch of rain through Saturday in San Luis Obispo and Santa Barbara counties, said meteorologist Tom Fisher.

“None of it will be showery or heavy,” Fisher said.

Only about a tenth of an inch of rain is expected in Los Angeles through Saturday, and temperatures will hover in the 60s during the drizzle before climbing into the 70s on Sunday, Fisher said.

The late-season storm continues California’s remarkable turnaround from what was shaping up to be a year on par with the worst years of the recent drought. Absent significant storms in November and January, California’s rain season was dramatically below average — particularly in the Southland.

But then in March, Fisher said, a large “blocking” pattern in the atmosphere that had steered storms away from the California coastline shifted and opened the floodgates.

Almost the entire region between San Luis Obispo and Los Angeles counties saw rainfall above and beyond seasonal averages for March, the weather service said.

Paso Robles received 272% its monthly average, while Ojai received 254% and Palmdale 155%, the agency said. Last month provided more than half of the season’s rainfall for much of the Southland.

The series of storms also helped replenish the Sierra Nevada snowpack, a precious resource for California in the spring and summer. The statewide snowpack was at 23% of average going into March and leapt to 52% of its annual average by April 1, the state Department of Water Resources said.

“These snowpack results — while better than they were a few weeks ago — still underscore the need for widespread careful and wise use of our water supplies,” DWR director Karla Nemeth said in a statement Monday. “The only thing predictable about California’s climate is that it’s unpredictable. We need to make our water system more resilient so we’re prepared for the extreme fluctuations in our water system, especially in the face of climate change.”

This week’s storm is relatively warm and isn’t expected to contribute significantly to the snowpack, officials said.

joseph.serna@latimes.com

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