A giant storm stretching some 2,000 miles across the United States is creating blizzard conditions from the southern Plains to the upper Midwest, paralyzing grain and livestock movement for at least a couple days, a forecaster said on Tuesday.

Moderate to heavy snows of 8 to 15 inches (200 to 380 mm) will blanket the central and northern Midwest, with some spots getting 20 inches more. In Chicago, local forecasters expect the city to see a near-record snowfall of up 2 feet.

The southern half the United States will miss the snow but get hit with freezing rain and ice.

"The largest area of the country we've seen so far this winter will be hit with moderate to heavy snow," said Mike Palmerino, a forecaster with Telvent DTN weather service. "Transportation will be treacherous for the next 48 hours."

Meat processor Cargill canceled second shifts at pork plants in Ottumwa, Iowa, and Beardstown, Illinois. Grain elevators across the southern Plains were working with limited shifts and icing on Midwest rivers was expected to slow loadings of grain barges headed to U.S. Gulf export markets.

The storm began in the western Plains wheat belt on Monday but precipitation was light -- a dusting to up to an inch of snow, Palmerino said.

But the system is gaining strength as it moves east. The eastern hard red winter wheat belt saw 2 to 4 inches of snow with similar amounts expected for Tuesday.

A blast of arctic cold is following the storm. Morning lows in the western Plains wheat belt dipped to 0 to minus 10 Fahrenheit (minus 17 to minus 23 Celsius). Wednesday and Thursday will be even colder when lows dip to minus 5 to minus 15 F.

The western Plains wheat crop is most vulnerable to the subzero temperatures, Palmerino said, as the snow cover is thin providing little to no protection from the frigid temperatures.

For the second straight week, Texas said its wheat crop deteriorated. The state late Monday rated 52 percent of its wheat poor to very poor versus 49 percent the week before.

The arctic air will move into the Midwest later in the week when lows dip to minus 5 to 5 F.

Palmerino's six to 10-day Plains outlook for Sunday to Thursday is for mostly below-normal temperatures and near to below-normal precipitation.

For the Midwest, Palmerino is calling for below to much-below normal temperatures and near to below precipitation.