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

Heavy precipitation is falling mostly in mountain areas. A flood watch in also in effect for the coast of central California, including the San Francisco Bay Area and Sacramento Valley.

Southern California is in desperate need of rain, but it could come far too fast this week, especially in areas recently burned by wildfires.

A stronger atmospheric river is set to hit Northern California on Monday and then hit Los Angeles County on Tuesday, aiding hopes of a more definitive end to a devastating fire weather season for Southern California.

The first storm from the tail end of an atmospheric river brought light to moderate rain throughout the Los Angeles area. A second storm is already making its way toward the region. The National Weather Service said the first storm system underperformed across most of the area.

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.