Meteorologists warn of tornadoes, hail as storm system hits Great Plains

Apr. 13, 2011: NOAA's Storm Prediction Center warns of severe weather in portions of Kansas and Oklahoma on Saturday. According to forecasters, there is a 60 percent chance of tornadoes, high wind and hail within 25 miles of a point in an area from Salina, Kan., to Oklahoma City. (AP Photo/NOAA)

Apr. 13, 2012: A satellite image taken at 1:45 a.m. EDT shows the Western and Central US remain cloudy as a low pressure system moves into Canada and another trough moves over the West Coast. This kicks up more rain and high elevation snow showers across most of the West. In the Plains, scattered thunderstorms develop along an associated frontal boundary. These storms turn severe with strong winds, large hail, and a few tornadoes. (AP Photo / Weather Underground)

A dangerous weather formation may lead to tornado outbreaks, severe thunderstorm and even hailstones as big as softballs, the National Weather Service said Friday.

Forecasters at the Storm Prediction Center in Norman, Okla., say there's a high risk of severe weather from Oklahoma City north to Salina, Kan. The severe storms are expected to strike Saturday afternoon and evening.

“Folks in the broader Great Plains should monitor this situation closely,” warned Jack Hayes, director of NOAA’s National Weather Service.

'Folks in the broader Great Plains should monitor this situation closely.'
— Jack Hayes, co-director of NOAA’s National Weather Service

The weather began to turn this afternoon, with the National Weather Service confirming a tornado had touched down in Norman, Okla., shortly after 4 p.m. near the University of Oklahoma campus.

There there were no immediate reports of injuries or damage.

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Severe weather is expected to stretch from northern Texas to Missouri, meteorologists said. The threat increases significantly Saturday, with a high risk of severe thunderstorms across parts of Kansas and Oklahoma. Moderate- and slight-risk areas surround the high-risk area for Saturday and stretch from extreme southwestern Minnesota to central Texas.

A tornado outbreak will be likely across the central and southern Plains from late Saturday afternoon lasting through the evening and into the overnight period.

Hailstones the size of golf balls or ping-pong balls fell on a sparsely populated region of Potter County, Texas, on Wednesday, following a severe and slow moving thunderstorm that drifted over the Texas panhandle. A meteorologist with the Amarillo, Texas, Weather Forecast Office told FoxNews.com that baseball- or even softball-sized hail could hit the South this weekend.

“I do think we’ll see larger hail over the next couple days,” the meteorologist, Justyn Jackson, told FoxNews.com. “It’s possible that we could maybe see baseball-sized hail, maybe even softball-sized. That’s not out of the realm of possibility.”

“Each individual storm that develops tomorrow is going to be capable of producing very large tornadoes,” said Russ Schneider, director of the NOAA Storm Prediction Center. The uncertainty is how many of these quick moving storms will form, he noted.

“You have to have a family emergency plan -- have an idea where you’re going to go, what actions you’re going to take should one of these storms hit your area.”

“Go to the lowest floor, put as many walls between you and the outside as possible,” he advised.

The Associated Press contributed to this report.