Evacuation orders and warnings have been issued for burn scar areas across Southern California as heavy rainfall threatens dangerous debris flows.Just before 5 p.m., the Los Angeles Fire Department reported a "large debris flow" that sent about 8 inches of mud across Mulholland Drive blocking the roadway.

An updated flash flood warning was issued by the NWS San Francisco CA on Thursday at 5:18 a.m. in effect until 9:15 a.m. The warning is for San Mateo, Santa Clara and Santa Cruz counties.

The National Weather Service warned that rain and flooding would intensify throughout the evening until around 10 p.m., bringing the risk of major flooding, debris flows and damaging winds.

An atmospheric river is expected to bring torrential rain to California this week, threatening parts of the state with flash floods and mudslides.

Areas charred by last month's wildfires in Southern California now face a new threat from a powerful, but fast-moving Pacific storm. Here's what you need to know about this threat.