The Los Angeles County Department of Public Works reported that Lake Hughes Road, between Pine Canyon and Dry Gulch roads in Lake Hughes, was closed due to mud and debris on the roadway. The agency asked the public to avoid the area and use alternate routes.
In Pomona, the Police Department reported flooding at the underpass at First Street, with several streets in the area either closed or affected by flooding, including South Reservoir Street, South Towne Avenue, East End Street, Garey Avenue and White Avenue.
"Received significant rainfall over our mountains last night and we are starting to see a response in our local main stem rivers. Not enough to reach monitor or flood stage, but finally seeing some flow," the National Weather Service's Los Angeles office tweeted at 8:33 a.m.
Shortly after 9 a.m., Doppler radar indicated heavy rain due to thunderstorms in south Orange County, and minor flooding expected to begin in Irvine, Mission Viejo, Rancho Santa Margarita, San Clemente, Laguna Beach, Dana Point and Laguna Niguel.
The Angeles National Forest said slick conditions due to rain or snow could prompt road closures in the forest. Tire or snow chain requirements could be in effect.
Forecasters said heavy downpours and small hail were possible in some areas through Sunday evening.
The Los Angeles County mountains were predicted to see rainfall rates of 1/2- to 3/4-inch per hour. Those rates prompted the NWS to issue a flash flood watch for the mountains, Antelope Valley and San Gabriel Valley through Sunday afternoon. The watch particularly applies to the Fish Fire and Lake Fire burn areas.
Storm soaks Inland Empire amid powerful winds
Residents near those burn scars should prepare for potential flooding impacts, officials said.
The weather was causing some power outages as well. The Los Angeles Department of Water and Power tweeted at that crews were working to restore power to affected customers in Hollywood, Highland Park and Playa del Rey, as quickly as possible, while working in challenging conditions.
By Sunday morning, 4.73 inches of rain had fallen at Stunt Ranch in the Santa Monica Mountains. The snow level remained high through Sunday morning, but could drop later in the day to as low as 3,000 feet, meaning "snow could accumulate on portions of I-5 near the Grapevine. This could cause major travel disruptions at the end of the weekend," according to the Weather Service.
Wind advisories were in place until noon in the greater Los Angeles area and the valleys, and until 6 p.m. in Orange County.
The storm is expected to pass through the region by Sunday night. Some lingering showers will be possible Monday morning, primarily in mountain areas, forecasters said.
City News Service contributed to this report.