One day after tornadoes tore through parts of Nebraska and Iowa, leveling dozens of homes, severe thunderstorms and high winds were expected across the central and southern Great Plains on Saturday.

Tornadoes and large hail were likely in northern Texas, Oklahoma and southeastern Kansas, forecasters said.

Tornado warnings were in effect for parts of western Oklahoma on Saturday morning and have since expired but the potential for tornadoes was expected to increase throughout the afternoon and early evening, the National Weather Service said.

As rich moisture surged northwestward, the outlook was “already very unstable,” said Ryan Jewell, a forecaster at the Weather Prediction Center of the Weather Service.

“It’s a fairly complicated scenario today because of the sheer number of storms,” he said. “They start interacting and there’s several different pockets of potential.”

In Norman, Okla., a city of about 130,000 people that is 20 miles south of Oklahoma City, the air was thick with moisture on Saturday morning as flag lines knocked against their poles.

That moisture was on a northwestward path, bringing with it the potential for an evolving system that could change in character as the day continues.

Excessive rainfall was likely in Kansas, Oklahoma, Texas and parts of Missouri, creating conditions for potentially damaging flash flooding.

By early Saturday afternoon, nearly 2 million people were under a tornado watch.

“We could really have quite a range of weather phenomena,” Mr. Jewell said. Hail over two inches in diameter and strong winds, some greater than 70 miles per hour, were expected.

The far-reaching storm system comes on the heels of tornadoes on Friday that struck several areas of Nebraska and Iowa, where at least nine people were injured as winds battered the region. Dozens of homes were razed, and an industrial building collapsed.

The Weather Service said that it had received more than 100 reports of tornadoes in at least five states in the Great Plains on Friday.