Rain from a powerful winter storm that swept across Southern California has begun to taper off, but another storm system was on the horizon for Christmas Day with showers and possible thunderstorms. Forecasters said Southern California could see its wettest Christmas in years and warned of flash flooding and mudslides.

The National Weather Service (NWS) issued "life-threatening" flash flood warnings for parts of Southern California. Follow Newsweek live.

An intense winter storm created flash flooding in Southern California, closing roadways and forcing residents to evacuate in parts of the Los Angeles region.

Strong winds and rain brought misery to California on Wednesday, with downed trees, flooding and intermittent power outages reported across the state. Multiple counties, especially in Southern California, are under flash flood warnings after an atmospheric river dropped inches of rain in the region.

Residents of Los Angeles spent the day before Christmas under rain showers and winds of around 40 mph, while the New England area braces for heavy snow later in the week.

An emphasis has been placed on burn scar areas that are more susceptible to flooding, mudslides and debris flows.

A strong atmospheric river is moving across Southern California, bring heavy rain and threatening mudslides in recent burn scar areas.

A sweeping flood watch stretching more than 800 miles along California’s coast and interior plains is in effect this week atmospheric rivers move through.