Bands of dangerous ice in the Northeast and the Midwest. The risk of a rare December tornado across parts of the South. And for the East Coast, temperatures that are more "Mele Kalikimaka" than "White Christmas."
It's a strange forecast for the last travel weekend before the holiday — and, for people caught in the worst of it, "a lot of misery," said Michael Palmer, a lead meteorologist at The Weather Channel.
Chicago and Detroit were already reporting icy conditions. Light snow across the central Great Plains and the western Great Lakes was expected to intensify over the weekend, coating Kansas City, Mo., and Milwaukee with up to 10 inches.
New England braced for ice Saturday and Sunday, which could lead to power lines and trees and knock out electricity.
The Penobscot County, Maine, Emergency Management Agency was in conference calls with the National Weather Service to see how serious the storm could be.
"Ice is ice," Michelle Tanguay, the agency's director, told NBC station WCSH of Portland. "Weight on power lines ... can still cause power outages. So even with the half of an inch to an inch of ice [in the forecast], you could still look at potential power failures."
And in the South, the tornado threat Saturday coincides with the first day of winter. The danger zone includes eastern Texas, northern Louisiana, Arkansas and western Mississippi.
The tornadoes could be as powerful as a 4 on what's known as the enhanced Fujita scale, meaning they could pack winds stronger than 166 mph, Palmer said.
The area of highest risk includes Memphis, Tenn., a hub for FedEx, just as final deliveries are going out for Christmas.
The storms are the result of a collision between arctic air pushing down from Canada and a welter of unusually warm air pushing up along the East Coast. The Weather Channel says 60 cities from Florida to New York could hit record highs Sunday.
The forecast high for Sunday was 66 in New York, 71 in Philadelphia and 72 in Washington — more like early October, and definitely not Jack Frost nipping at your nose. Philadelphia could beat its all-time high for any day in December, 73 degrees, set on two days in 1998.
Atlanta, Baltimore, New Orleans, Orlando, Fla., and Raleigh, N.C., could all beat daily records Saturday, and Orlando should be in the mid-80s on Sunday, The Weather Channel reported.
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The first wave of the winter storm dumped snow in Salt Lake City on Thursday, triggering more than 230 flight cancellations, according to the flight-tracking website FlightAware.
Because the system moved in from the western desert, the rain and snow that fell wasn't just heavy; it was gritty — what meteorologists call "dirty rain." That was causing major problems for crews trying to repair power lines.
"The rain last night when it started was very dirty," Dave Eskelsen, a spokesman for Rocky Mountain Power, told NBC station KSL of Salt Lake City. "That dust and wet rain has enough minerals in it that can actually conduct electricity over the insulators."
"You get some sparking, and wooden poles and cross arms can actually catch fire in this weather," he said.
But the real headache will come Saturday and Sunday, when many people try to get a jump on holiday travel. The icy spell due in New England on Sunday will stretch from Burlington, Vt., into Maine and Quebec, Palmer said.
The National Weather Service issued a variety of weather warnings for a large band from northern Texas to Maine. The Weather Channel called it a "holiday travel nightmare."
New York City, Washington and Boston are due to escape without snow or ice. All three could be in for rain and thunderstorms in the run-up to Christmas.
M. Alex Johnson of NBC News contributed to this report.