CHICAGO (Reuters) - A colossal winter storm stretching from New Mexico to Maine hit the heartland of the United States with snow, high winds and freezing rain on Tuesday, and experts said the worst was still to come as the storm moved northeast and temperatures were set to plunge.
The storm, expected to affect as much as a third of the U.S. population, created blizzard conditions from the southern Plains to the upper Midwest, paralyzing grain and livestock movement and threatening near-record snowfall.
Ice and sleet created dangerous travel conditions and forced the cancellation of thousands of flights.
President Barack Obama was briefed on the storm and preparations for emergency relief. The National Weather Service has issued storm watches, warnings and advisories in more than 30 states, and blizzard warnings for eight: Illinois, Iowa, Indiana, Kansas, Michigan, Missouri, Oklahoma and Wisconsin.
Moderate to heavy snowfalls of 8 to 15 inches will blanket the central and northern Midwest, with some places getting 20 inches more. In Chicago, local forecasters expect to see accumulations of up to 2 feet.
In the Northeast, already facing a wintry mix of snow and sleet, the storm could dump 12-18 inches of snow on Boston through Wednesday.
After the snow lets up Wednesday, some affected areas will be in a deep freeze until the weekend, with daytime temperatures below freezing and "really dangerous wind chills," said National Weather Service spokesman Pat Slattery.
Wall Street financial markets were operating normally on Tuesday, but officials were making plans for Wednesday, when dangerous icing was possible.
In Washington, the federal government said workers could take unscheduled leave or telecommute on Tuesday because of the treacherous travel conditions.
"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."
The southern half of the United States will miss the snow but parts of it may get hit with freezing rain and ice.
Eleven states, from Oklahoma to Rhode Island, have taken the Federal Emergency Management Association up on an offer to deploy personnel as needed, and the agency has positioned items such as meals, blankets and generators for rapid delivery if needed.
WHEAT, CATTLE THREATENED
The storm is expected to wreak havoc on agricultural operations in the Plains states, threatening the dormant winter wheat crop, cattle herds and grain deliveries.
Key farm states of Oklahoma, Kansas and Missouri are being hammered by what forecasters said could be a record combination of frigid conditions and snowfall. Between 12 and 24 inches of snow are forecast in an arc from southeastern Kansas to southern Michigan and northern Ohio.
Grain elevators across the southern Plains were working with limited shifts and icing on Midwest rivers was expected to slow loading of grain barges headed to U.S. Gulf export markets.
Meat processor Cargill Inc said it will reduce production at two U.S. Midwest pork plants ahead of the storm.
Chicago soybean futures rose more than 1 percent early on Tuesday, hitting their highest level since July 2008 as the frigid winter storm boosted feed demand.
Freezing temperatures were proving dangerous for Oklahoma's 5.1 million head of cattle, its Department of Agricultural Food and Forestry said. "Hypothermia and dehydration are the two things we worry about," said spokesman Jack Carson.
Dallas-Fort Worth International Airport closed for 2 1/2 hours early on Tuesday due to ice, just as thousands of American football fans began arriving in Dallas for the Super Bowl game on Sunday. Ice made main roads in the city almost impassable.
Plows were pulled from the runways at Kansas City International Airport at one point due to blowing snow and low visibility, and near-whiteout conditions prompted the closure of Interstate 70 in central Missouri.
The top U.S. airlines United Continental, Delta Air Lines and American Airlines had canceled more than 5,400 flights by Tuesday afternoon.
FlightAware.com, a website that offers live flight tracking, estimated total cancellations at more than 6,450.
The National Weather Service said the ice and sleet could turn into one of the biggest blizzards in more than 40 years in Chicago, with as much as 2 feet of snow expected. The snow is expected to be accompanied by high winds of more than 40 miles per hour and plunging temperatures.
Chicago faces a blizzard warning through Wednesday afternoon. Many traders at the Chicago Mercantile Exchange were planning to stay downtown on Tuesday night. A CME Group official said the exchange was monitoring the weather forecasts but had not put any contingency plans in place.
In New York City, snow, sleet and freezing rain made for a messy, slippery commute. Subways and buses were running but with delays and crowding.
"It's far from a picturesque scene. It's an icy, wet mess," said meteorologist John Davitt of NY1 television.
Many in the financial industry took the latest severe weather in stride, though.
"We have a couple of people working from home who live long distances from the office. Other than that, our office is pretty staffed," said Michael Sheldon, chief market strategist at RDM Financial in Westport, Connecticut.
"Companies that really will be impacted are companies in rural areas where employees have to drive a significant distance," Sheldon said.
States of emergency have been declared in Wisconsin, Illinois, Missouri and Oklahoma.
In Tulsa, Oklahoma, conditions were so bad that the Tulsa World newspaper will not publish for the first time in its history, said publisher Robert E. Lorton III. Many subscribers couldn't find their Tuesday editions under the snow.
The storm is unlikely to hurt first-quarter U.S. economic growth, but is another problem for state and local governments already beset by budget problems, Moody's Analytics Chief Economist Mark Zandi told Reuters Insider.
Many cities and towns have already drained their snow removal budgets for the year after a series of storms in January. February has started with no respite at all.
(Additional reporting by Bob Burgdorfer, Christine Stebbins, Caroline Valetkevitch, Corrie MacLaggan, Ann Saphir, Carey Gillam, Wendell Marsh, Lauren Keiper, Ellen Wulfhorst and Ed Stoddard; writing by Anthony Boadle and Ros Krasny; editing by Mohammad Zargham and Eric Walsh)