Arctic cold returns to wrap up 2014: Dangerous wind chills ahead for west, midwest
By Jon Erdman
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 has opened the Arctic freezer door once again headed into the final few days of 2014.
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.
Early Taste of Chill Arrives
The second Christmas week storm system, Winter Storm Eris, brought snow to the Upper Midwest and appears to have opened the Arctic gates into the U.S. for the rest of 2014 into the first few days of the new year.
Temperatures over the long Christmas holiday weekend fell significantly, particularly over parts of the Rockies and Plains. Denver saw its first subfreezing high of the month on Friday (Dec. 26), when the mercury got no higher than 20. Bismarck reached a low of 2 below zero that same day, marking its first subzero low in over three weeks.
By Saturday, Oklahoma City's high only reached 38, a 25-degree drop from the previous day and its coldest since Dec. 1; afternoon temperatures stalled in the 40s in Dallas-Ft. Worth on Sunday.
Monday morning temperatures dipped into the teens below zero in parts of northern North Dakota, northern Minnesota and northwest Wisconsin. Wind chills dipped as low as 36 degrees below zero at Minot Air Force Base, North Dakota early Monday.
The cold will continue to spread this holiday week. Let's break down the forecast details.
Forecast: Even Colder Weather Ahead
This cold blast will set up camp over the Rockies, Great Basin, Plains and Upper Midwest through the first half of the week, before easing off a bit. Some of that cold air will eventually ooze its way into at least parts of the Deep South and Northeast in time for the New Year's holiday.
(FORECAST: 10-Day Forecast Maps)
As the frigid air invades, biting north winds will make it feel even worse. The National Weather Service has already posted wind chill advisories or warnings for parts of 11 states from Minnesota and Iowa to higher elevations of southwest Washington and northern Oregon.
(INTERACTIVE: NWS Wind Chill Alerts)
Wind chills to 20 below or colder could reach as far south as southeast Colorado, western Kansas, Iowa and western Wisconsin by early Tuesday. The combination of cold temperatures and winds may lead to frostbite on exposed skin in 30 minutes or less in these areas.
Highs in single-digits/teens: Much of the interior Northwest, northern and central Rockies, High Plains, mid-Missouri Valley, Upper Midwest
Subfreezing highs: As far south as West Texas, southern Oklahoma, the Ozarks, Ohio Valley, and New Jersey (Tuesday and/or Wednesday)
Subzero lows: Northern Plains, central High Plains, Upper Midwest, northern and central Rockies, mountains of the Northwest, and Great Basin
Record cold highs: Possible on the High Plains including Denver, Pueblo, Colorado, and Cheyenne, Wyoming
Why the Change?
The reason behind this pattern change should sound familiar if you remember last winter.
This 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.
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 were 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. The cooler weather ahead may be just enough for Seattle to avoid setting a new record for the warmest December on record, but it will be a close call.
The U.S. tallied 4,740 daily warm records (record daily highs or record warm daily lows) from December 1 to December 25, compared to just 272 daily cold records. That's a ratio of more than 17 record highs for every record low.
MORE ON WEATHER.COM: 20 Coldest Large U.S. Cities
Highs in single-digits/teens: Much of the interior Northwest, northern and central Rockies, High Plains, mid-Missouri Valley, Upper Midwest
Subfreezing highs: As far south as West Texas, southern Oklahoma, the Ozarks, Ohio Valley, and New Jersey (Tuesday and/or Wednesday)
Subzero lows: Northern Plains, central High Plains, Upper Midwest, northern and central Rockies, mountains of the Northwest, and Great Basin
Record cold highs: Possible on the High Plains including Denver, Pueblo, Colorado, and Cheyenne, Wyoming
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