By Mark Guarino
CHICAGO (Reuters) - Central Colorado is the only part of the United States that can expect to have a white Christmas on Thursday, despite storms that have brought rain and fog to many parts of the country, the National Weather Service said on Wednesday.
The forecast comes amid one of the busiest travel times of the year. The AAA travelers' association estimates that 98.6 million people, up 4 percent from last year, will travel more than 50 miles during the period from Tuesday to Jan. 4.
The NWS said a storm system moving east from the Pacific would bring snow showers from Washington state to the western High Plains on Thursday.
The greatest accumulations, from 4 to 7 inches, are expected in the higher elevations of the central and northern Rocky Mountains.
A winter storm watch is in effect from Thursday afternoon through Friday morning in Colorado's Teller and northern El Paso counties with 5 to 10 inches of snow expected.
The Colorado Department of Transportation said emergency crews would work 12-hour shifts in the Denver metropolitan area on Thursday. It warned that drivers on Interstate 70 should expect significant delays.
The Christmas forecast came as severe thunderstorms menaced the U.S. Southeast and emergency workers in Mississippi surveyed damage from tornadoes that killed at least four people and injured 20.
The NWS canceled a winter weather advisory in Chicago as higher temperatures turned Wednesday’s forecast snowfall to rain.
The flight tracking website FlightAware reported 1,857 U.S. flight delays on Wednesday. Cancellations totaled 284, most of them at O'Hare International Airport in Chicago.
The Chicago Department of Aviation forecast that more than 4.2 million travelers were expected to pass through the city's O'Hare and Midway airports from Dec. 23 to Jan. 6.
Heavy fog delayed some flights at San Francisco International Airport, Detroit Metropolitan Wayne County, Philadelphia International and New York's John F. Kennedy International airports.
American Airlines said on Tuesday it would let travelers change reservations without penalty on Wednesday and Thursday. The deal is available at O'Hare, St. Louis, Milwaukee, Detroit, and other Midwestern airports.
(Reporting by Mark Guarino; Editing by Eric Beech)