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.

The National Weather Service says an outbreak of severe storms could spawn tornadoes, heavy snow and high winds.

More than 100 million people in the U.S. will be in the path of an intense March storm starting Friday as the sprawling multi-day system threatens fires, blizzards, tornadoes, and flooding as it tracks eastward across the Great Plains.