Forecasters say Saturday storms 'life threatening'

As states across the middle of the country prepared for the worst, storms were already kicking off in Norman, Okla., where a twister whizzed by the nation's tornado forecasting headquarters but caused little damage.

It was only the second time in U.S. history that the Storm Prediction Center issued a high-risk warning more than 24 hours in advance, said Russ Schneider, director of the center, which is part of the National Weather Service. The first time was in April 2006, when nearly 100 tornadoes tore across the southeastern U.S., killing a dozen people and damaging more than 1,000 homes in Tennessee.

This weekend's outbreak could be a "high-end, life threatening event," the center said.

The strongly worded message came after the National Weather Service announced last month that it would start using terms like "mass devastation," ''unsurvivable" and "catastrophic" in warnings in an effort to get more people to take heed. It said it would test the new warnings in Kansas and Missouri before deciding whether to expand them to other parts of the country.

Friday's warning, despite the dire language, was not part of that effort but just the most accurate way to describe what was expected, a weather service spokeswoman said.

It's possible to issue earlier warnings because improvements in storm modeling and technology are letting forecasters predict storms earlier and with greater confidence, said Chris Vaccaro, a spokesman for the National Weather Service. In the past, people often have had only minutes of warning when a siren went off.

"We're quite sure tomorrow will be a very busy and dangerous day in terms of large tornadoes in parts of the central and southern plains," Vaccaro said. "The ingredients are coming together."

The worst weather is expected to develop late Saturday afternoon between Oklahoma City and Salina, Kan., but other areas also could see severe storms with baseball-sized hail and winds of up to 70 mph, forecasters said. The warning issued Friday covers parts of Illinois, Iowa, Kansas, Missouri, Nebraska, Oklahoma and Texas.

The weather service confirmed a tornado touched down about 4 p.m. Friday near the University of Oklahoma campus in Norman, where it is based. Non-essential personnel at the storm center and students were ordered to take shelter, officials said.

Video from television helicopters showed several buildings damaged in the city of about 100,000 about 20 miles south of Oklahoma City, but Oklahoma Department of Emergency Management spokeswoman Keli Cain said there were no reports of serious injuries.