A man places sandbags at the top of a street lined with K-rail and sandbags in Glendora, Calif., as the city and residents prepare for possible flooding Thursday, Feb. 27, 2014
The first wave of a powerful Pacific storm spread rain and snow early on Friday through much of California, where communities endangered by a wildfire just weeks ago now faced the threat of mud and debris flows.
The barren mountain slopes looming above neighborhoods in the foothills east of Los Angeles were still holding after the first bout of rain, said police Lt. Matt Williams. Mandatory evacuation orders were issued for about 1,000 homes in the area on Thursday.
"We are cautiously optimistic," Williams said.
Numerous traffic accidents occurred on slick or flooded roads across Southern California, and a 10-mile (8-kilometer) stretch of Pacific Coast Highway west of Malibu was closed as a precaution against possible rockslides from a fire-scarred section of the Santa Monica Mountains.
Rain was also falling in the central coast counties, in the San Francisco Bay region and in the Central Valley. Winter storm warnings were in effect in the Sierra Nevada for heavy snowfall.
Forecasts called for the storm to last through Saturday in California, bringing some relief amid a long-running drought, and to spread east into similarly parched neighboring states. Phoenix was expecting its first noticeable precipitation in two months.
Around San Francisco Bay, the storm led to an urban and small stream flood warning, as rain in excess of a half-inch an hour moved in, according to the National Weather Service. Wet roadways and crashes slowed the morning commute, and there were isolated power outages.
Some arriving flights at San Francisco International Airport were delayed by more than four hours, according to the Federal Aviation Administration.
The storm's full force was expected to be felt later Friday morning, with possible thunderstorms and rains up to an inch per hour, the National Weather Service said.