Long before powerful storms began to roll through the Midwest Saturday afternoon, forecasters had warned of "life-threatening" tornadoes, thunderstorms and hail.
Here are some details on why these warnings _ which came on Friday _ were so unusual.
JUST HOW RARE? This marks the second time in U.S. history that the Storm Prediction Center has issued a high-risk warning more than 24 hours in advance.
WHAT HAPPENED LAST TIME: The first high-risk warning more than a day early came in April 2006, when nearly 100 tornadoes tore across the southeastern U.S. In all, a dozen people died and more than 1,000 homes were damaged in Tennessee.
WHY EARLIER WARNINGS: In the past, people often have had only minutes of warning when a siren went off. But improvements in storm modeling and technology let forecasters predict storms earlier and with greater confidence, the National Weather Service says. The Storm Prediction Center is part of the service.
NEW WARNING LANGUAGE: The weather service is now testing words such as "mass devastation," "unsurvivable" and "catastrophic" aimed at getting more people to take heed. The warnings are being experimented with in Kansas and Missouri. The "life-threatening" warning for this round of storms, 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.
ON THE GROUND: Tornadoes were spotted across the Midwest and Plains. Storms were reported in Kansas, Iowa, Nebraska and Oklahoma. Emergency officials in Iowa said that either high winds or a tornado damaged a hospital in Creston, southwest of Des Moines, but officials said no one was injured. In Nebraska, baseball-sized hail shattered windows and ripped siding from houses. In Oklahoma, more than 5,000 people gathered for a rattlesnake hunt in Woods County scattered when a tornado touched down there, an official said. And in Thurman, Iowa, officials tell AP this small western community of about 250 people has been severely damaged by a possible tornado, saying about 75 percent of the town was destroyed.
Storm Prediction Center: http://www.spc.noaa.gov/