Omaha: Severe storms pounded the central United States on Tuesday, producing baseball-sized hail and unconfirmed reports of tornado touchdowns, forcing voting to be suspended during primary elections in Iowa and halting flights at a Nebraska airport.
A dozen people suffered minor injuries after being struck by the outsized hailstones while fleeing for cover at a Walmart in Blair, Nebraska, north of Omaha, Fire Chief Kent Nicholson said.
"It sounded like someone was drilling our building with a hammer. It was deafening in our shop area," said Nicholson, who was at work during the storm.
Eppley Airfield spokesman Joe Rotterdam said flights were halted for four hours on Tuesday at the Omaha airport. Thirty-three flight were canceled Tuesday due to flash flooding, gusting wind and nickel to quarter-sized hail, he said.
Storm chasers reported at least eight unconfirmed tornado touch-downs in Nebraska, one in Iowa and another in Wyoming, the National Weather Service said.
Hail, ranging from golf ball to tennis ball size, also pelted parts of Wyoming, the northern half of Nebraska and the southwestern corners of South Dakota and Iowa, the National Weather Service said.
Voting in Iowa`s primary election was suspended late on Tuesday afternoon in Pottawattamie County and Montgomery County as poll workers, along with voters, sought shelter.
Winds reported at up to 90 mph (145 kph) tore roofs off two motels in Missouri Valley, Iowa.
A derecho - a long-lived, wide line of thunderstorms that produces damaging winds - threatened the region on Tuesday night and is expected to move east into Wednesday morning, said AccuWeather.com senior meteorologist Alex Sosnowski.
"These storms can knock down trees, cause power outages and travel mayhem for the Wednesday morning commute," he said.
National Storm Prediction Center forecaster Bill Bunting in Norman, Oklahoma, said the strongest storms on Tuesday could produce tornadoes, with the possibility of a tornado rated EF-2 or higher and winds peaking at 135 mph (217 kph) or more.
A tornado watch was in effect on Tuesday night for much of Nebraska, southwest Iowa and northwest Missouri, and central Iowa was under a flash flood warning, the weather service said.
On Wednesday, the storms were expected to move into eastern Missouri, central Illinois, Indiana, Kentucky, southern Ohio, parts of Tennessee and West Virginia, forecasters said.
AccuWeather.com said the storms could bring 2 to 4 inches (5-10 cm) of rain, with flash flooding possible in some areas.