A powerful storm system stretching from Canada to Mexico is threatening millions of Americans. More than 40 million people across 18 states are preparing for storms that could last into the middle of next week.

A powerful storm system stretching from Canada to Mexico is threatening millions of Americans. More than 40 million people across 18 states are preparing for storms that could last into the middle of next week, CBS News' Omar Villafranca reports.

There was an outbreak of severe storms overnight. Dozens of twisters were reported overnight in Oklahoma, Nebraska and Kansas, where eight tornadoes were reported within two hours.

Storm chasers in the state captured the beginnings of a tornado tossing a semi-truck onto its side. The team continued to follow the twister as it tore through the state's southwest. A mobile home in bloom suffered a direct hit. No injuries were reported.

Much of the damage included downed powerlines, which are believed to have sparked a grassfire.

Nebraska police said more than 1,000 were without power on Saturday morning.

More tornadoes are expected to touch down throughout the weekend. The National Weather Service also reports damaging winds, large hail and heavy rain from Texas to the Great Lakes.