CHICAGO A monster winter storm stretching from New Mexico to Maine laid down a sheet of ice on the Plains and lower Midwest on Tuesday, turning to snow as it moved north, and experts said the worst was yet to come.
The storm, expected to hit as much as a third of the U.S. population, blanketed a wide swath with ice and sleet, creating dangerous travel conditions.
In Dallas, area roads were covered with "a good sheet of ice," according to Texas Transportation Department spokesman Mark Pettit.
The Dallas-Fort Worth international airport closed for 2 1/2 hours on Tuesday just as thousands of football fans began arriving in the city for the Super Bowl game on Sunday.
The top U.S. airlines United Continental, Delta Air Lines, American Airlines and Southwest said they had canceled more than 4,000 flights ahead of the storm.
More than 1,200 of those flights were in and out of Chicago area airports, which are major hubs for the airlines.
In Washington, the federal government said that workers could take unscheduled leave or telecommute on Tuesday because of the treacherous travel conditions.
The weather was so bad in Omaha, Nebraska that the local chapter of the American Meteorological Society canceled its monthly meeting at the IceHouse Sports Bar and Grill.
Omaha police are asking drivers to avoid the interstate highway systems, as icy conditions have caused numerous accidents.
Schools have closed all along path of the storm. Chicago public schools, famous for staying open no matter the weather, were open Tuesday but considering whether to close on Wednesday.
"I have to come out tomorrow anyway, even if the school closes, to tell kids to go home," said Robyn Vogell, 51, who helps both public and parochial school children cross the street on the city's Northwest Side. Vogell said she had already stocked up on groceries to ride out the storm.
While the big storm has not yet hit Chicago, residents have already set out lawn chairs and plastic buckets to mark their parking spots so they can park when they get home from work. Chicago has 274 snow plows ready to go, along with 120 garbage trucks equipped with plows.
At the CME Group's downtown trading floor in Chicago, many traders who buy and sell agricultural commodities, financial contracts and options were planning to stay downtown overnight, storing suitcases in the coat room. But trading was not expected to be affected.
Bob Margherio, owner of Mac Do It Best Hardware in the St. Louis suburb of Webster Groves, Mo., said on Tuesday that he was completely out of ice melt product, snow blowers, generators, flashlights and nearly out of batteries.
"I ordered 18 tons of ice melt two days ago, but the supplier told me this morning that I was out of luck," said Margherio.
Snow, sleet and freezing rain made for a messy, slippery commute in New York City, where forecasters said the wintry mix would last into Wednesday as the storm moved in from the Midwest.
"It's far from a picturesque scene. It's an icy, wet mess," said meteorologist John Davitt of local NY1 television.
The city's subways and buses were running but with delays and crowding due to weather-related equipment problems, authorities said.
Traffic was slowed on highways in and around New York City, and speed restrictions were imposed on the George Washington Bridge and the Tappan Zee Bridge, both of which span the Hudson River, due to the weather conditions, authorities said.
Wall Street financial markets were operating normally on Tuesday morning but officials were making plans for Wednesday.
In New England, light to moderate snow was already falling during the morning commute in Boston.
Illinois, Missouri and Oklahoma were among states that declared a state of emergency even before the storm hit. White-out conditions were reported on Interstate 44 between Oklahoma and Missouri, closing part of it.
"Everyone should stay inside today and not drive," Missouri Gov. Jay Nixon said on local television.
By the time the storm front reaches the upper Midwest later on Tuesday, 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 two feet of snow expected.
The snow is expected to be accompanied by high winds of more than 40 miles per hour and plunging temperatures.
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.
In Oklahoma, 45 mile-per-hour winds and temperatures at 9 degrees or lower were proving dangerous for the state's 5.1 million head of cattle, said Jack Carson, spokesman for the Oklahoma Department of Agricultural Food and Forestry. "Hypothermia and dehydration are the two things we worry about," Carson said.
After the snow lets up Wednesday, affected areas will be plunged into a deep freeze for the end of the week, with single digit temperatures in the daytime and "really dangerous wind chills," said National Weather Service spokesman Pat Slattery.
Power outages were fewer than expected, according to utilities, with about 25,000 households in Texas without electricity but few problems in Kansas, Oklahoma or Missouri.
(Additional reporting by Corrie MacLaggan, Carey Gillam, Doris Frankel, Bob Burgdorfer, David Hendee, Ann Saphir, Bruce Olson, Wendell Marsh, Lauren Keiper, Ben Fenwick and Ellen Wulfhorst; Editing by Greg McCune)