took a long December vacation, but a significant pattern change opened the Arctic freezer door as 2014 came to a close.

Wednesday morning put an exclamation point on the cold snap, as the tiny unincorporated village of Daniel, Wyoming, plummeted to 48 degrees below zero. That wasn't the wind chill -- that was the actual temperature. It's the coldest temperature recorded anywhere in the contiguous United States in all of 2014.

The cold is already suspected to be the cause of a man's death in Omaha, Nebraska, where temperatures fell below zero Monday night.

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Let's take a look at what we've seen and 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, , opened the Arctic gates into the U.S. for the rest of 2014 into the first few days of the new year.

Here are a few "cold highlights" that illustrate the first half of the final week of 2014:

Highs in the teens or colder: Parts of the interior Northwest, northern and central Rockies, High Plains, mid-Missouri Valley, Upper MidwestRecord cold highs and lows:High Plains on Tuesday includingDenver,Pueblo, Colorado, andCheyenne, WyomingSubfreezing highs: As far south as West Texas, southern Oklahoma, the Ozarks, Ohio Valley, and New Jersey (Wednesday)Subzero lows:Northern Plains, central High Plains, Upper Midwest, northern and central Rockies and Great Basin (Wednesday)

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 38 degrees below zero at Rugby, North Dakota early Monday. Ironically, one of the hottest locations in the U.S. in the summer months, Thermal, California, tied a daily record low of 25 degrees Monday.

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Temperatures reached the double digits below zero Tuesday morning in at least 12 states from Idaho to Wisconsin (13 if one counts Mount Washington in New Hampshire). The coldest spots were near the Wyoming-Montana border, with 36 below zero reported at Lamar Ranger Station in Yellowstone National Park and 34 below zero at West Yellowstone Gate in Montana.

Subzero cold stretched as far south as the Sangre de Cristo mountains of northern New Mexico, including Taos (low of minus 6) Tuesday morning. Wind chills from 35 to 40 degrees below zero were observed in Casper, Laramie, and Jackson, Wyoming.

Overnight Tuesday into early Wednesday morning, Denver plummeted to minus 19 degrees, which smashed a 116 year old record low that was set on December 30, 1898. Incidentally, Denver only "warmed" to 1 degree on Tuesday afternoon, which was also a new record low maximum temperature that obliterated the previous record set in 1915.

Alliance, Nebraska also set a new record low for December 30 when the thermometer dropped to 28 degrees below zero.

Laramie, Wyoming, hit 34 below zero; at one point the city's wind chill was 55 below zero thanks to a 13-mph wind.

Early Wednesday morning approximately 80 percent of the U.S. land area and 68 percent of the U.S. population was at or below freezing.

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As the frigid air invaded, biting north winds made it feel even worse. The most dangerous wind chills were found in southeast Wyoming, the Nebraska Panhandle, and northeast Colorado. These areas saw wind chills between 40 and 55 below zero at times through Wednesday morning.

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Western States Not Spared This Time

Because arctic air is so cold, and therefore so dense, it tends to move in a shallow layer close to the ground. Often that layer of frigid air is too shallow to overcome the high elevations of the Rocky Mountains, so the air instead plunges south and stays east of the Rockies.

In this case, however, unusually strong high pressure came south with the cold air -- and at the same time, was spinning up low pressure over the lower Colorado River Valley.

The pressure difference forced cold winds to circulate from the high pressure toward the low pressure, helping shove arctic air through the mountain passes.

This has resulted in some locally very strong winds in the West. Winds gusted up to 78 mph Tuesday in Farmington, Utah, and several tractor-trailers were knocked over on Interstate 15.

Winds have gusted over 50 mph Tuesday in parts of the San Francisco Bay Area, knocking down trees and causing power outages. A 119-mph gust was clocked atop Mount Lincoln (elevation 8,300 feet) between Sacramento, California, and Reno, Nevada.

This setup also brought chilly temperatures deep into the Southwest. Even normally mild places like experienced a .

Why the Change?

The reason behind this pattern change should sound familiar if you remember .

This week, a bulge of high pressure aloft has diverted 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.

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 were much warmer than average in the Rockies and Great Basin.

, 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, .

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 4,960 daily warm records (record daily highs or record warm daily lows) from December 1 to December 28, compared to just 312 daily cold records. That's a ratio of almost 16 record highs for every record low.

For Some, 2014 Was a Record Cold Year

Meteorologists record countless ambient air temperature readings every hour, and these temperature readings are used to detemerine the daily highs and lows for each city. From that data, the average daily temperature is calculated, which can then be used to determine the average annual temperature.

Using that convention, the National Weather Service in Little Rock notes that . Chicago experienced the 14th coldest year on record, and it was the c. And , a feat that broke the previous record set in 1875.

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The Weather Channel meteorologist Michael Palmer explains that "overall, for the second straight year, there were more record cold temperature records set than record warm temperatures across the country. The final figures settled in at 49,000 cold records versus 39,00 warm records."

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