A powerful storm dumped snow and rain as it moved across California, shutting down a major interstate highway and prompting flood watches in areas scarred by wildfires.

California Highway Patrol officers escorted vehicles out of Tejon Pass on Wednesday as traffic was halted in both directions along Interstate 5 north of Los Angeles, a dispatcher said.

"There are abandoned cars everywhere," said Wendy Gardner, a manager at Madd Bailey's Pub in Pine Mountain Club, where as much as 10 inches (25 centimeters) of snow fell. "We got hit around 2:30 in the morning, and it hasn't stopped."

Nearly a foot (30 centimeters) of snow was reported at the ranch community of Lockwood Valley in Los Padres National Forest, northwest of Los Angeles, the National Weather Service said.

Along the coast, a record 4.14 inches (10.5 centimeters) of rain was recorded at the Santa Barbara airport, topping the date's old mark of 2.45 inches (6.2 centimeters) set in 1943.

Flash flood watches were issued for areas of Santa Barbara, Ventura and Los Angeles counties. A flood warning was posted for the Malibu areas burned by recent wildfires.

The unstable atmosphere brought the threat of thunderstorms, which in the past have led to dangerous debris flows in and below burn areas, the Weather Service said.