Dec 20 (Reuters) - A huge swath of the United States will face heavy snow, below-freezing temperatures, and dangerous wind chills this week, likely leading to flight delays and impassable roadways during one of the busiest travel periods of the year.
The National Weather Service forecasts potentially hazardous weather conditions into the middle of the week, extending from the Northwest and Great Plains regions of the country to the central and southern Appalachian area.
"With such a large and powerful storm system... it is imperative that travelers check the latest forecast before venturing out," the Service said in a short range forecast posted on its website on Tuesday.
A surge of Arctic air crossing the country behind a cold front is expected to create blizzard conditions in parts of the Plains and Great Lakes region, while a flash freeze could occur from the mid-South to the East Coast, according to the Service.
Residents of the affected areas fretted on social media about travel disruptions, the prospect of getting trapped in their houses, and the plight of their neighbors without homes.
"It is unconscionable that we have people living without shelter in Chicago winters at all, much less during a blizzard at Christmas," posted Twitter user @laurie_merrell on Tuesday morning.
Heavy snow is also likely across the northern Rocky Mountains and the Pacific Northwest, with the greatest snowfall expected in the higher terrain of the Cascade Mountains, northern Idaho, northwest Montana, and western Wyoming, the National Weather Service said.
U.S. winter storms have shifted northward and increased in frequency and intensity over the past 70 years, according to the U.S. Global Change Research Program.
Snowstorms are expected to dump higher volumes of snow as a result of climate change, according to the Environmental Defense Fund, because the planet evaporates more water into the atmosphere as it warms, leading to more overall precipitation.
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