A winter storm threatens to bring blizzards and ice to parts of the U.S., hampering holiday travel

A powerful winter storm was sweeping east from the Plains on Sunday, driven by what meteorologists describe as an intense cyclone, setting off a chain reaction of snow, ice, rain and severe weather expected to affect much of the country.

Snow and strengthening winds spread across the Upper Midwest on Sunday, where the National Weather Service warned of whiteout conditions and possible blizzard conditions that could make travel impossible in some areas. Snowfall totals were expected to exceed a foot across parts of the upper Great Lakes, with up to 2 feet (61 centimeters) possible along the south shore of Lake Superior.

In the South, meteorologists warn of severe thunderstorms expected to signal the arrival of a sharp cold front — sometimes referred to as a ''Blue Norther'' — bringing a sudden temperature drop and strong north winds that will end days of record warmth across the region.

The snowy holiday season in the Upper Midwest and Northeast comes as springlike warmth continues in much of the nation's midsection and South, where record high temperatures had Santa sweating in recent days.

The high temperature in Atlanta is forecast to be around 72 degrees Fahrenheit (22 degrees Celsius) on Sunday, continuing a warming trend after climbing to 78 F (about 26 C) to shatter the city's record high temperature for Christmas Eve, the National Weather Service said. Numerous other record high temperatures were seen across the South and Midwest on the days after Christmas.

But that record heat is quickly coming to an end, forecasters say.

A cold front is expected to bring rain to much of the South late Sunday night into Monday, bringing much colder weather on Tuesday. The abrupt change will drop the low temperature in Atlanta to 25 F (minus 3.9 C) by early Tuesday morning. The colder temperatures in the South are expected to continue through New Year's Day.

The storm is expected to intensify as it moves east, drawing energy from a sharp clash between frigid air plunging south from Canada and unusually warm air that has lingered across the southern United States, according to the National Weather Service.

It follows thousands of flight delays and cancellations across the Northeast and Great Lakes regions earlier this weekend due to snow, as thousands took to the roads and airports during the busy travel period between Christmas and New Year's.

On the other side of the country, California was experiencing a fairly dry weekend after powerful storms battered the state with heavy rains, flash flooding and mudslides. At least four people were killed including a man who was found dead Friday in a partially submerged car near Lancaster, the Los Angeles County Sheriff's Department reported.

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