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.

Potentially catastrophic rain is heading toward Los Angeles -- a region already scarred by recent extreme weather and climate events, making it more vulnerable.

Forecasters said heavy rain was expected to drench much of Southern California through the holidays, and officials warned the storm could be deadly.

An even more potent atmospheric river-fueled storm is on a collision course with California after a first storm triggered deadly flooding and evacuations over the weekend in Northern California.