California Faces Renewed Threat as Another Atmospheric River Storm Approaches

California faces another atmospheric river storm, threatening flooding, landslides, and power outages on Wednesday as millions of residents recover from previous destructive storms, one of which breached a levee last weekend.

Flood watches cover central and Northern California, where saturated grounds are primed for flooding and rapid runoff. The new storm is predicted to exacerbate existing damage, bringing up to four inches of rain and 40 mph winds to valleys, according to the National Weather Service Weather Prediction Center.

In Watsonville and Santa Cruz County, officials have issued mandatory evacuation orders for high-risk flood areas. San Mateo County, south of San Francisco, has declared a local state of emergency and activated its emergency operations center.

“Prepare now for flooding, downed trees, and power outages,” National Weather Service forecasters in the San Francisco Bay Area warned Tuesday evening, cautioning residents about the incoming major rain and wind.

In south Sacramento County, responders are racing to repair a 34-mile levee system along the Cosumnes River, protecting vineyards and cattle ranches, before the storm hits on Wednesday.

This storm is part of a series of atmospheric river storms, which climate scientists predict will persist throughout the month. Atmospheric rivers are long, narrow streams in the atmosphere transporting most water vapor outside the tropics, per the National Oceanic and Atmospheric Administration.

“These storms typically bring heavy or extreme rainfall and snowfall rates over relatively short periods of time,” explained Daniel McEvoy, a climatologist at the Western Regional Climate Center.

Atmospheric rivers contribute up to 50% of California’s annual precipitation and cause about 84% of flood damage in the Western states. While recent heavy rains have somewhat alleviated California’s drought, scientists caution that these storms won’t immediately fix severe groundwater and soil moisture deficits.

Daniel Swain, a climate scientist at UCLA, noted at least two additional atmospheric river storms are forecast in the next five days, potentially causing more severe flooding.

“This is not just a one-and-done. This is an ongoing sequence,” Swain emphasized. “The big flood risk comes with this succession of progressively stronger storms, which looks like the pattern we’re in.”

Governor Gavin Newsom’s office announced on Twitter that the state’s operations center is at its highest emergency level. The flood operations center is coordinating efforts like distributing sandbags and setting up shelters and is prepared to deploy staff to hospitals and ambulance strike teams.