'Thundersnow' storm in US Midwest blamed for two deaths

A major winter storm in the US Midwest that is already blamed for two deaths has blanketed several states in up to 17in (43cm) of snow.

More than half of Interstate 70 in Kansas and Kansas City International Airport were closed as snow fell up to two inches per hour in some areas.

Parts of Colorado, Kansas and Oklahoma saw at least a foot of snow, in some places accompanied by lightning.

"Instead of pouring rain, it's pouring snow," one weather official said.

National Weather Service meteorologist Scott Truett said the heavy "thundersnow" resulted from an unstable air mass, much like a thunderstorm.

In one 30-minute period, Topeka, Kansas saw three inches of snow.

"It came on fast,'' Jen Carlock told the Associated Press news agency as she shovelled snow from her car.

"We're going to test out traction control on the way home.''

The huge system moved to the north and east on Thursday evening, leaving behind 17in in Hays, Kansas, 13in in Wichita and 10in in northern Oklahoma and parts of Nebraska.

Kansas City airport officials said they were preparing to reopen on Friday morning. More than 320 flights at Lambert Airport in St Louis were also cancelled.

Schools and legislatures in multiple states were closed on Thursday, and Missouri Governor Jay Nixon announced a state of emergency. The University of Missouri cancelled classes for one of the only times in its 174-year history.

Kansas Governor Sam Brownback warned residents to stay off the roads.

The storm has reached as far as Arkansas, where some areas were hit by a combination of hail, sleet and freezing rain.

Bad road conditions from the storm contributed to two fatal vehicle accidents on Wednesday.

An Oklahoma teenager died when his pickup truck skidded into oncoming traffic and a 19-year-old woman was killed in Nebraska when a sport utility vehicle lost control, crossed the road median, and struck her car.

Alex Sosnowski, a meteorologist with forecaster Accuweather, said a spin-off storm could dump heavy snow on the north-eastern New England states. By its end, the storm could affect a total of 24 states, he said.

Many of the Midwest states hit have suffered from an extended drought, and some residents were thankful for the precipitation.

Vance Ehmkes, a wheat farmer in western Kansas, told the Associated Press that the 10-12 inches already fallen was "what we have been praying for".