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 powerful atmospheric river storm is pounding parts of California with torrential rain, strong winds and snow and leading to issues from San Francisco to Los Angeles, including areas recently impacted by deadly wildfires.

The storm, which forecasters said could produce tornadoes, is expected to strengthen Friday and move towards the central US.

A cross-country storm will explode in strength as it moves over the central United States Friday, delivering extreme weather to millions through the weekend, including the chance of multiple strong tornadoes.