Arctic Cold Returns to Wrap Up 2014 in West, Midwest

By Jon Erdman

Published Dec 25,2014 10:10AM,EST

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Big Blast of Cold Air Next Week

The Weather Channel winter weather expert Tom Niziol says cold air will return next week to welcome in 2015. 

Arctic cold air of the magnitude we saw in November has, largely, taken a December vacation, so far.
Emphasis on the phrase "so far".
While a Midwest/East Christmas week storm had more rain than snow, a significant pattern change ahead will open the Arctic freezer door once again headed into the last week of 2014.
(MORE: Expert Analysis | Winter Storm Central)
Let's delve into a forecast outlook. If you're a weather geek, we'll then explore why this is happening and go into some perspective on how warm December has been.

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Highs vs. Average Next Tuesday

Blue (yellow) shaded areas indicate colder (warmer) than average high temperatures next Tuesday.

Forecast

The second Christmas week storm system, Winter Storm Eris, will bring snow to the Northwest, Rockies and Upper Midwest appears to open the Arctic gates into the U.S. for the rest of 2014 into the first few days of the new year.
Friday into this weekend, highs in the teens, even some single digits, will reappear over parts of the Northern Plains and Upper Midwest. Colder air will also plunge down the Plains. Highs may languish in the 40s (or colder) as far south as Oklahoma City and Dallas-Ft. Worth.
The Southwest will even feel the chill. Freeze warnings have been posted near Phoenix for Saturday morning as temperatures are expected to drop below or near freezing.
(FORECAST: 10-Day Forecast Maps)
An even colder blast is expected to nosedive into the Rockies, Great Basin, Plains and Upper Midwest Monday and Tuesday of next week. Some of our longer-range forecast guidance then suggests some of that cold air may eventually ooze its way into at least parts of the Deep South and Northeast in time for the New Year's holiday.
Here are a few potential "cold highlights" in the first half of next week:

• Highs in single-digits/teens: Northern Plains, Upper Midwest, northern/central Rockies
• Subfreezing highs: Parts of Ohio Valley, mid-Mississippi Valley, Southern Plains next Tue. into Wed.
• Subzero lows: Northern Plains, Upper Midwest, northern/central Rockies

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Pattern Change Ahead

Why the Change?

The reason behind this pattern change should sound familiar if you remember last winter.
Next week, a bulge of high pressure aloft will divert the polar jet stream north of the Arctic Circle in Alaska and Canada's Yukon and Northwest Territories, then southward deep into the western Lower 48 states.
This is a classic arctic outbreak pattern, tapping cold air from Alaska's interior and northwest Canada and sending it deep into the U.S. In the colder months, when it's relatively warm in Alaska, it is probably quite cold somewhere (if not most locations) in the Lower 48 states.

December 2014's Warmth

Temperature departures from average for the period of Dec. 1-20, 2014 over the Lower 48 states.   (NOAA/CPC)

A Warm December

This expected colder end to the month will be quite a change for many, especially those in the West.
As you can see in the map at left, the first roughly three weeks of December have been much warmer than average in the Rockies and Great Basin.
The first two weeks of the month were the second warmest on record in Salt Lake City, topped only by December 1889, over 6 years before Utah became the 45th state admitted to the Union.
Livingston, Montana set a new December record high (64 on Dec. 12). According to the National Weather Service in Billings, Montana, it was warmer on the morning of Dec. 12 in Livingston than Atlanta, Tucson, Las Vegas and Tampa.
The West Coast has been unusually mild as well. Seattle averaged 6.8 degrees warmer than average for the first three weeks of December and recorded its 19th consecutive warmer-than-average day Monday. If our forecast temperatures for Seattle through the end of the month prove correct, it will be the warmest December on record at Sea-Tac Airport.
Through December 21, the U.S. had tallied 3,840 daily warm records (record daily highs or record warm daily lows), compared to just 259 daily cold records.

MORE ON WEATHER.COM: 20 Coldest Large U.S. Cities

#20: Boston (Avg. Dec-Feb Temp: 31.8 degrees)

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Boston's all-time record low was -18 degrees set on Feb. 9, 1934. Once every 1-2 years the city shivers in subzero cold. Subfreezing temperatures occur 94 days a year, there. (Photo: Darren McCollester/Getty Images) 

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