California Braces for Floods and Snow as Big Storm Nears Coast

The first of two large moisture streams are coming ashore in Northern California and will spread rain further south through Thursday.

Northern California will likely receive 3 to 5 inches (7.6 to 12.7 cm) of rain, while central areas are due to get 2 to 4 inches and further south will see 1 to 3 inches, said Marc Chenard, a senior branch forecaster at the US Weather Prediction Center. Snow will be heaviest Thursday across higher elevations of the Sierra Nevada. As much as 3 feet (1 meter) may fall at the highest peaks, the weather service said.

“It is going to slide down the coast as we go through today into tomorrow,” Chenard said. “It is enough for some flooding impacts, especially along the coast and central valley today into tomorrow.”

The streams of moisture, known as atmospheric rivers, are swirling off the Pacific Ocean and can bring beneficial rain and snow or devastating floods depending on their strength and speed. The first system is forecast to move quickly, reducing some of its destructive power, but the outlook for the second one that will arrive Sunday is less sure.

The California Department of Water Resources will begin releasing water through the Oroville Spillway on Wednesday, according to a social media post. Heavy rain and flooding damaged the spillway in 2017.

California’s reservoir system has a dual purpose, one is to help with flood control and the other is to capture water for drinking and agriculture during winter months. This can mean the state has to release water from its lakes as large storms arrive to make sure they can handle the output of incoming storms.

Flood warnings and watches are up across parts of California, along with high wind watches and winter storm warnings for the Sierra Nevada range.

(Updates with snow forecast in second paragraph.)

Top photo: Ocean Beach after a rain storm in San Francisco, California, US, on Thursday, Jan. 5, 2023. A powerful storm with hurricane-force gusts has begun to wind down after ripping across California, leaving behind power outages, flood threats and road closures just hours before another drenching is set to wash over the state. Photographer: Shelby Knowles/Bloomberg.