[1/5] High water levels caused by stormwater flood Discovery Park, located in the convergence of the Sacramento River and the American River, in Sacramento, California, U.S. January 4, 2023.
The latest "atmospheric river" - an airborne current of dense moisture flowing from the ocean - was expected to drench much of California ahead of a Pacific storm front bringing additional showers to low-lying areas and more snow to the Sierra Nevada Mountains through Thursday.
Authorities warned that heavy downpours would likely unleash flash flooding and mudslides, especially in areas where the ground remains saturated from rains that soaked northern California days earlier.
Governor Gavin Newsom declared a state of emergency on Wednesday to support the state's winter weather hazards response, and activated California's flood operations center.
A separate storm system hovering on Wednesday over parts of the Midwest was forecast to drift off the East Coast by Friday.