AMNA NAWAZ: Welcome to the "NewsHour."

We are starting tonight with two major stories.

First, a tornado has plowed into Little Rock, Arkansas, and nearby towns with reports of heavy damage and many people injured.

Amateur video captured the huge funnel cloud on the horizon.

And driving, straight-line winds whipped trees and sent sheets of rain into the city.

The storm flipped cars, tore away rooftops and knocked out power to thousands.

Emergency crews rushed out to search for victims and perform rescue operations.

It was all part of a massive storm front that affected at least 15 states from the Great Lakes to the Deep South.

Joining us now by phone is Bill Bunting.

He's operations chief for the NOAA Storm Prediction Center in Norman, Oklahoma.

Bill Bunting, welcome and thank you for joining us.

What can you tell us about the strength and the scale of the storm that just hit Little Rock?

BILL BUNTING, Operations Chief, Storm Prediction Center, National Oceanic and Atmospheric Administration: Well, at the moment, the information that we have, as you noted, suggests there was a very strong tornado touchdown across portions of the Little Rock metro.

And we have received reports of a number of injuries, damage to neighborhoods, overturned vehicles, widespread power outages.

Those details will become clearer as the evening progresses.

And it's, unfortunately, all part of a very large weather system that extends from Eastern Iowa down into Eastern Texas and that will continue racing east overnight over a large part of the Ohio Valley.

AMNA NAWAZ: We know some 28 million people are under tornado watches this afternoon.

Where is it headed next?

What should they be bracing for?

BILL BUNTING: Well, the storms right now are moving towards the Mississippi River Valley area.

We have also got a separate area of storms approaching Chicago.

And, at the moment, a tornado emergency is in effect northwest of Memphis.

So the storms remain quite dangerous, reports of very large hail, baseball-sized, destructive straight-line winds, perhaps in excess of hurricane-force, and the continued threat of tornadoes, moving east overnight, as far east of Columbus, Ohio, through Nashville, even into Northwest Alabama, so a large area affected, and, unfortunately, a really active start, early start, to our severe weather season.

AMNA NAWAZ: And, Bill, briefly if you can, for the places that have already been hit, is the worst behind them?

BILL BUNTING: In the areas hardest hit, likely yes.

There are a few storms to the west, and that could hamper rescue and recovery operations.

But the most significant threat for tornadoes, certainly in Little Rock, has shifted south and east.

But folks will have to be watching out for lightning, perhaps even some hail over the next few hours.

AMNA NAWAZ: That is Bill Bunting joining us on the phone tonight, the operations chief for the NOAA Storm Prediction Center in Norman, Oklahoma.

Bill, thank you for joining us.

BILL BUNTING: Thank you.