Los Angeles and Ventura counties were placed under an updated flood advisory by the National Weather Service on Wednesday at 2:45 a.m. The advisory is in effect until 4 p.m.

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

Floods turned deadly in Northern California as the latest atmospheric river slammed the region over the weekend, dropping nearly a foot of rain in some places. Meanwhile, more heavy rain and flooding are forecast to persist and expand into Southern California through the Christmas holiday week.

Flash flooding and mudslide risks continue in Northern California and will rise in Southern California through Christmas Day as heavy snow blocks Sierra Nevada roads.

A powerful atmospheric river storm will bring life-threatening flooding, 80 mph winds, and up to 12 inches of rain to Southern California through Christmas week, according to the National Weather Service.

Evacuation orders have been issues for 10 areas around Los Angeles as the area braces for a bomb cycle that may bring flash floods