CHICAGO » Freezing rain. Snow. Thunderstorms. Even tornadoes. Much of the nation braced for foul weather on one of the busiest travel weekends of the year, as a wet winter storm created travel worries from Chicago and Detroit to Boston and New York.

Forecasters were predicting everything from freezing rain and snow in the north to torrential rain in the Ohio Valley and Appalachia and possibly even tornadoes in the South.

The worst of the storm was expected to hit Midwest population centers this evening, giving some travelers a window at the start of the holiday rush to get through airports and along highways with little disruption. But by late morning, the number of flight cancellations and delays were both creeping up into the low hundreds, most of them at major hub airports, according to aviation tracking website FlightAware.com.

It’s bad timing for the estimated 94.5 million Americans planning to travel by road or air during this holiday season, which runs from today through New Year’s Day, and those hitting the roads for some last-minute shopping.

"This is a particularly strong storm with very warm, near record-breaking temperatures in the East and very cold air in the Midwest, and that contrast is the sort of conditions that are favorable for not only winter weather but also tornadoes," said National Weather Service meteorologist Ed Danaher in College Park, Md.

The weekend storm was forecast to arch more than 2,000 miles from Texas to northern New England in several bands of weather that, depending on local the temperature, could produce up to 6-12 inches of snow in the northern edge, an icy mix in the middle and soaking rains and thunderstorms in the South.

It was already bringing significant ice accumulations to Oklahoma, southern Missouri and northern Arkansas, splitting trees and snapping power lines. That was expected to change over to snow by tonight.

In the Upper Midwest, forecasters expect 6-8 inches of snow north and west of Chicago and into Wisconsin.

Dennis Richmond, 72, was worried about a possible delay to his son’s flight today from Washington, D.C., to Madison, Wis., which could get up to 8 inches of snow. He said he didn’t tell his son to change his itinerary, though, because there were few alternatives, and that he still planned to drive the roughly 140 miles from La Crosse to pick him up.

"The thing is, trying to book another flight at this time of year is next to impossible," he said. "I just want to alert him to the fact he might be delayed."

Icy weather snarled traffic in Oklahoma on Friday. Police in Oklahoma City blamed at least one traffic death on the weather. Forecasters said up to a half-inch of ice could accumulate across the middle of the state, from the Texas border in the southwest to the Missouri border in the northeast.

In Wisconsin and Michigan, slippery roads from freezing rain forced some schools to cancel classes. A woman sleeping in a hotel in Holland in western Michigan was injured when a motorist lost control of his car on an icy street early Friday and slammed into the wall outside her room, MLive.com reported.

In New England, communities were planning for a bit of everything — snow, sleet and rain — but were most concerned about the threat of freezing rain.

The National Weather Service predicted that parts of Maine could get more than a half-inch coating of ice, which would make roads treacherous and cause widespread power outages.

"The best advice for everyone is just to really pay attention. With every few hours, we’re going to get better information," Maine Emergency Management Agency spokeswoman Lynnette Miller said Friday.

The weather service issued a flash flood watch from Arkansas northeastward through parts of Missouri, Illinois, Indiana and Ohio, with up to 4 inches of rain projected. With falling temperatures, some of that could be freezing rain tonight in the St. Louis area, weather service meteorologist Jon Carney said.

In Indiana, the National Weather Service posted flood warnings along southern and central Indiana streams and predicted the highest flood crests along the East Fork of the White River since April 2011.

While the Midwest and Plains were preparing for ice and snow, residents down South were concerned about tornadoes, which forecasters said were possible this weekend even though they are uncommon this time of year. The area most threatened stretched from central and northeastern Texas through Louisiana, Mississippi, Arkansas and southeast Missouri, where 80 mph wind gusts and flash flooding were possible.

Tom Kines, an AccuWeather meteorologist, said a northern cold front clashing with warm, humid air from the South is causing the unsettled weather.

"I think there’s a high likelihood there will be severe storms with hail and damaging wind" in parts of the South, Kines said. "Whether or not there’s tornadoes, that’s tough to say, but I will say the conditions are right."

Weekend temperatures could surpass 70 degrees in Nashville this weekend and approach that in New York City as well, Kines said. But by Sunday night, the storm will be hammering the Northeast, where residents could be treated to a rare winter thunderstorm.

If there is a silver lining, it’s that Christmas happens mid-week this year, AAA spokeswoman Heather Hunter said.

"When a holiday falls on a Wednesday it gives travelers more flexibility of either leaving the weekend before, or traveling right before the holiday and extending the trip through the following weekend," Hunter said.

Associated Press writers Shelley Adler in Washington, D.C.; Kelly P. Kissel in Little Rock, Ark.; David Sharp in Portland, Maine; and Dinesh Ramde in Milwaukee contributed to this report.