A powerful storm system stretching from Canada to Mexico is threatening millions of Americans. More than 40 million people across 18 states are bracing 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. The National Oceanic and Atmospheric Administration confirmed two tornadoes touched down in Texas and one touched down in Kansas Saturday.

Storm chasers in Kansas 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 power lines, 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.

"Severe thunderstorms and some flash flooding can be expected across portions of the Plains, Mississippi Valley and Ohio Valley this weekend," the weather service said.