"The cold front with the heaviest rain and snow will be through the area by about 10 a.m.," the National Weather Service said. "Most of the area received from 1 to 3 inches of rain in the last 24-hours and will be transitioning to two days of showers and possible thunderstorms."
Forecasters said minor urban flooding was possible in many parts of Los Angeles County.
The city of Los Angeles temporarily closed the Sepulveda Basin around midday. The closure runs on Burbank Boulevard between Balboa Boulevard and the 405 Freeway, and on Woodley Avenue from Victory to Burbank Boulevard.
Also closed for the duration of the storm was the on-ramp to southbound 5 Freeway from Lankershim Boulevard in Sun Valley, where Caltrans crews were installing three extra pumps to prevent the highway from flooding.
The Los Angeles County Public Works Department warned residents about the potential for debris and mudflow in parts of the north county.
Los Angeles County Supervisor Kathryn Barger advised residents to take appropriate precautions in light threatened mudflows.
Storm bringing rain, snow to SoCal amid flash flood warning for part of LA County
"Our County will experience another storm system this weekend that brings an increased threat of flash flooding, along with debris and mudflows," she said in a statement early Saturday. "I am asking residents who were recently impacted by wildfires -- such as the Agua and Fish Fires -- to remain extremely vigilant and aware of your surroundings. Burn areas and hillsides in particular are vulnerable to debris and mudflows.
"The best way to stay safe is to keep tracking weather conditions, sign up for your local emergency alert systems, and listen to your local news broadcasts. If you receive an evacuation message from local law enforcement officials, follow their directions and don't hesitate. Prioritizing safety is key this Easter holiday weekend."
Los Angeles Mayor Karen Bass said late Saturday morning that the storm had caused power outages in some neighborhoods, and Los Angeles Department of Water and Power crews "were working to restore power quickly and safely."
The storm will be accompanied by gusty winds and the possibility of thunderstorms Saturday night into Sunday, with the best chances on Sunday.
"These thunderstorms on Sunday could produce small hail, gusty winds, frequent lightning and possibly even a small tornado or waterspout," the Weather Service said.
Caltrans said the 5 Freeway was open through the Grapevine, but drivers should expect high winds, rain, possible snow and California Highway Patrol escorts.
City, county extend Los Angeles shelter programs for weekend storm
Forecasters said one to two feet of snow could fall at elevations above 6,000 feet, "with even higher amounts at the highest peaks."
"Snow levels should remain above the Grapevine but there is a 10 percent chance of a snow burst under a thunderstorm," according to the Weather Service. "Wind gusts from 60 to 65 mph will pummel the mountains as well but they will diminish Saturday afternoon."
A winter storm warning will be in effect through 11 p.m. Sunday for the San Gabriel Mountains and the 5 and 14 freeway corridors, with forecasters warning that "travel could be very difficult to impossible."
Cooler temperatures were also in the forecast for Easter weekend, with most areas not getting out of the 50s.
Temperatures were expected to warm slightly by Monday, as much as 10 degrees in some areas, "but maximum temperatures will still end up 4 to 8 degrees below normal."
City News Service contributed to this report.