A powerful storm dropping drenching rain on flood-prone Southern California is raising concern among forecasters that it could produce a dangerous, widespread outbreak of tornadoes, damaging winds and fires along with a blizzard as it crosses the entire United States in the coming days.

Evacuation warnings and orders have been issued for Los Angeles communities near the Eaton, Palisades and Sunset fire burn zones ahead of the rain.

A colossal storm is threatening to bring severe weather to much of California this week and could impact travel over the Grapevine. Here's what to know.