Incoming heavy rain from an atmospheric river-fueled storm that slammed into the West Coast early Wednesday is threatening mudslides and debris flows in Southern California and has already prompted evacuations in the Los Angeles area.

The storm, which forecasters said could produce tornadoes, is expected to strengthen Friday and move towards the central US.

The same powerful storm that battered Southern California with heavy rain and brought blizzard conditions to the San Bernardino Mountains is putting millions on alert from coast to coast.