By early afternoon the latest storm system had dumped more than 5 inches of rain in Refugio Pass in the Santa Ynez Mountains just to the northwest of El Capitan Canyon.
A sheriff's helicopter returning to an airport after the canyon incident spotted a car swamped by water and a woman screaming for help from higher ground nearby was hoisted to safety, Zaniboni said.
Throughout the day, forecasters issued a flurry of flash flood warnings and lower level advisories as the storm moved from north to south down the length of California with high rates of rainfall.
"Storm #2 packing some punch," the Los Angeles-area National Weather Service office wrote.
In Northern California, a section of state highway flooded in Sonoma County and water rose to the wheel hubs of cars along low-lying streets in and around Santa Cruz. Runoff and rockslides in the Santa Monica Mountains west of Los Angeles forced the California Highway Patrol to close all canyon roads in the Malibu area.
Forecasters warned of potential debris flows from wildfire burn scars in Southern California.
Storm warnings were also posted up and down the Sierra Nevada after the second storm dropped nearly 2 feet of snow at higher elevations. The mountains of Southern California have also been accumulating snow on peaks that were barren in years of drought.
Along the coast, big surf was rolling ashore and forecasters said waves could build to 30 feet on the Central Coast.
The third storm was forecast to be the strongest of the trio. The National Weather Service says winds could gust up to 140 mph over the Sierra ridgetops Saturday night and Sunday.
Storms since the fall have caused drought to retreat from nearly half the state.
As of Thursday night, downtown Los Angeles had received 9.82 inches of rain since the start of the water year on Oct. 1, nearly 4 inches above normal to date and well above the 3.76 inches that had fallen in the same period a year earlier.
This post has been updated.
AP writer Scott Sonner in Reno, Nevada, contributed to this story.
