(Changes dateline, byline, adds Buffalo color)
By Ian Simpson
WASHINGTON, Dec 26 (Reuters) - A powerful winter storm that has claimed at least five lives pounded the U.S. Midwest and Northeast and snarled post-Christmas travel on Wednesday after rare tornadoes pummeled the Gulf Coast.
Heavy snow and high winds prompted National Weather Service blizzard and winter storm warnings for the Ohio River Valley and into the Northeast. Fifteen inches (37.5 cm) of snow were recorded at New Baltimore, Michigan, as the storm headed north and east.
About 1,500 U.S. flights were canceled on Wednesday, according to FlightAware.com, a site that tracks flights. Some 170 flights also have been called off for Thursday, and several airlines waived ticket change fees for affected customers.
All four runways at Philadelphia International Airport were open on Wednesday, but some travelers still faced some canceled flights.
Mary Mazzoni, 25, an environmental writer from Scottsdale, Arizona, had to book an alternate flight on a different airline after her original flight to Phoenix was canceled. She is scheduled to ar rive in Phoenix late on Wednesday.
"It's a little annoying. But I'm trying to keep a good attitude about it," said Mazzoni, who was returning to Arizona after visiting relatives for the Christmas holidays.
The National Weather Service warned that 12 to 18 inches (30 to 45 cm) of snow were expected in northern New England, with snow falling through Friday morning. The storm was accompanied by freezing rain and sleet, making driving treacherous, it said.
Across central New York, about 25 minor accidents were reported in a two-hour span Wednesday along major highways, said New York State Police Sergeant Nick Merritt.
"Right now we have additional patrols out on the roads in case we need them," he said.
If predictions of up to 16 inches (40 cm) of snow come true, Buffalo will still be well below average for snowfall, said Bill Hibbert, a meteorologist for the National Weather Service. Buffalo's snowfall is 23 inches (57.5 cm) below normal for the season.
Severe thunderstorms and widespread rain were expected from southeast Virginia to Florida, the agency said. The eastern counties in North Carolina and South Carolina were under tornado watches or warnings for much of the day.
The winter storm had swept out of the southern Great Plains and through the South on Tuesday. The system spawned at least 34 tornadoes.
A Texas man died after an accident involving a toppled tree in the road. Icy roads contributed to the deaths of four people in auto crashes in Oklahoma and Arkansas, according to police.
Twisters struck in Alabama, Mississippi, Texas and Louisiana, flattening houses and causing injuries, according to the weather service. The storm also dumped record snowfalls in north Texas and Arkansas.
Nearly 200,000 homes and businesses had no electricity in Arkansas and Alabama on Wednesday. (Reporting by Colleen Jenkins and Ian Simpson; Additional reporting by Corrie MacLaggan, Eileen O'Grady, Steve Olafson, Dave Warner and Neale Gulley; Editing by Paul Thomasch and Sandra Maler)