December thaw is bad news for winter lovers, good news for everyone else

Bad News for Winter Lovers

By Nick Wiltgen, The Weather Channel

After several rounds of arctic chill this fall, most of the country will enjoy a long spell of warmer-than-average weather over the next week or two -- just as meteorological winter has begun.

(MORE: November 2014 Shattered Cold, Snow Records)

A jet stream pattern that has encouraged cold air masses from near the Arctic Circle to rush southward into the U.S. will change over the next several days, allowing much milder air from the Pacific Ocean and Gulf of Mexico to become the dominant influences on temperatures nationwide.

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Computer forecast models are in strong agreement that this will allow unseasonably warm weather to take over a large part of the Lower 48 later this week and on into next week.

(MORE: National 10-Day Forecast Maps)

This means temperatures will stay well above freezing, day and night, across much of the Deep South this week and probably next week as well.

Meanwhile, subzero lows and single-digit highs in the north-central states should give way to high temperatures at or above freezing at times, allowing some of the snowpack to melt. In areas where snow cover melts completely, temperatures could surge even higher, as snow cover has a refrigerating effect. Snowpack prevents sunlight from warming the ground underneath and reflects more sunlight directly back to outer space, making it more difficult to get the air near the ground to warm up.

Based on current forecasts, the warming trend will be more obvious at night than during the day; by this weekend, high temperatures will be at or slightly above average for most of the country, but low temperatures will be 10 to 20 degrees above average across a huge swath of the West, the Plains, and the Southeast.

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Crazy wintery snow from fall 2014
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December thaw is bad news for winter lovers, good news for everyone else
A tree in Middleton, Idaho. So many of our trees look like this! Today, more dense fog and freezing temps. High of 27. Yellow air quality. Photo: @KTVBChar We're on the air now! Join us on @ktvb7
As icy cold Canadian air settled over the eastern two-thirds of the U.S. bringing snow and bitter cold, NOAA's GOES-East satellite captured this infrared view of what looks like a frozen blanket over the region. NOAA's GOES-East satellite provides visible and infrared images over the eastern U.S. and the Atlantic Ocean from its fixed orbit in space. In an infrared image taken on Nov. 18 at 12:30 UTC (7:30 a.m. EST), the cold air over the eastern and central U.S. appears to look like a blanket of white, but it's not all snow. Infrared data shows temperature, so although the eastern two-thirds of the U.S. appears to appear is if snow covers the ground, the blanket is in fact cold clouds. However, snow does lie under that blanket in the Upper Midwest, Ohio Valley, and Canada, where it will continue in those areas through Thursday, Nov. 20. To create the image, NASA/NOAA's GOES Project takes the cloud data from NOAA's GOES-East satellite and overlays it on a true-color image of land and ocean created by data from the Moderate Resolution Imaging Spectroradiometer, or MODIS, instrument that flies aboard NASA's Aqua and Terra satellites. Together, those data created the entire picture of the storm and show its movement. After the storm system passes, the snow on the ground becomes visible. GOES satellites provide the kind of continuous monitoring necessary for intensive data analysis. Geostationary describes an orbit in which a satellite is always in the same position with respect to the rotating Earth. This allows GOES to hover continuously over one position on Earth's surface, appearing stationary. As a result, GOES provide a constant vigil for the atmospheric "triggers" for severe weather conditions such as tornadoes, flash floods, hail storms and hurricanes. Image credit: NASA/NOAA GOES Project, Dennis Chesters
The scene from Transit Road, a NYSEG truck among those stuck in the #LakeEffect http://t.co/BCCGWcYChp
View of the wall of snow clouds coming into Buffalo http://t.co/rWuNL4OGEq
There is a wall of snow coming off the lake into #Buffalo. Hold your loved ones. #Snow #Weather @WKBW http://t.co/Z28bkOUb9D
Hey @JimCantore my wife is 5'7" I'd say we're at 4 feet in Lancaster, NY and still coming! http://t.co/7iUDaRpfTg
The scene from Transit Road, a NYSEG truck among those stuck in the #LakeEffect http://t.co/BCCGWcYChp
This snow doesn't scare me... 😎
NOAA's automated snow mapping system shows the snow cover across North America on November 18, 2014. 
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Perspective: Cold Spells Dominate 2014

While 2014 has certainly had its warm days, they have tended to be the exception rather than the rule in much of the central and eastern U.S.

In fact, temperatures have been below average for the year to date across most of the country east of the Rockies. Temperatures have been farthest below average in a swath encompassing the entire Mississippi River Valley and much of the Great Lakes. In these areas, temperatures were 2 to 4 degrees below the historical average for the first 11 months of the year, according to data from the High Plains Regional Climate Center.

It's been the eighth-coldest year to date on record in Illinois, based on NOAA climate analysis for January through October. Missouri, Iowa, Indiana and Arkansas are also having one of their 12 coldest years of the past 120. (State-by-state data through November will be released in mid-December.)

For cities such as Chicago and Minneapolis, even a December with just average temperatures would result in 2014 being the coolest calendar year since 1996.

The pattern is well represented in the number of record highs and lows so far this year. Through Nov. 30, NOAA's National Climatic Data Center says there have been 33,013 record high temperatures in the Lower 48 this year -- but also 47,402 record lows. For just the month of November, there were more than four times as many record lows (8,977) as record highs (2,022).

One part of the country, however, has been consistently warm. California, Nevada and Arizona are experiencing their warmest year to date on record.

And the warm weather isn't going away there, either -- even though sometimes big pattern changes take weather away from one region and move it somewhere else, the Southwest will hold on to its warmth this time even as the rest of the country shakes off the frosty conditions.

The shift to a warmer regime just puts the central and eastern U.S. where most of the rest of the planet has been all year; 2014 is on track to be the warmest year on record worldwide.

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December thaw is bad news for winter lovers, good news for everyone else
Toronto, Canada. 22nd Dec, 2013. Trees fell across Toronto damaging power lines and cars. Freezing rain clung to every surface across the Greater Toronto Area, felling trees and power lines. © Victor Biro/Alamy Live News
Toronto, Canada. 22nd Dec, 2013. Large trees fell across Toronto under the weight of the ice that coated them. Multiple Freezing rain clung to every surface across the Greater Toronto Area, felling trees and power lines. © Victor Biro/Alamy Live News
Toronto, Canada. 22nd Dec, 2013. Large trees fell across Toronto under the weight of the ice that coated them. Multiple Freezing rain clung to every surface across the Greater Toronto Area, felling trees and power lines. © Victor Biro/Alamy Live News
Toronto, Canada-February 5, 2013: The city has declare an extreme cold alert..Heavy snow fall causes drivers many problems. Comm
Toronto, Canada-February 5, 2013: The city has declare an extreme cold alert..Heavy snow fall causes drivers many problems. Comm
Saskatoon, Saskatchewan, Canada. 21 December 2013. On the first official day of winter, an Arctic high pressure system causes extremely cold temperatures of below -25C in Saskatoon and other parts of Western Canada. © Felix Choo/Alamy Live News
Unseasonably cold weather freezes Toronto Harbor solid, creating a reflective skyline seen in sheets of ice atop Lake Ontario
Chicago, USA. 21st January 2014. Lake Michigan waves toss chunks of ice into the air at snowy North Avenue Beach after the latest lake effect snowstorm. The polar vortex has returned with frigid temperatures. © Todd Bannor/Alamy Live News
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