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.

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.

Wind gusts were forecast to top 50 mph in some areas. In Pico Rivera, a tornado with wind speeds reaching 85 mph traveled about a mile through a residential area of the city.