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Posted at 02:11 PM ET, 12/20/2011

Mild finish to December for much of U.S.

With all due respect to the blizzard that’s now winding down across a small portion of the Southern Plains, winter continues to be a near ‘no show’ almost everywhere else.

Yes, 8-16 inches of snow fell in a narrow band across southwestern Kansas and along the nearby High Plains in the past 24 hours. And blizzards in that part of the country are particularly dangerous because the blowing snow effectively eliminates visibility with so few trees in the way of the wind. I’ve been through them there and it can be really scary.


Temperature departures from normal (anomalies) since Thanksgiving. (NOAA/ESRL.)
But in so many places around the rest of the country where it’s supposed to be cold and snowy, it’s not, it hasn’t been, and won’t be for a while.

The temperature anomalies since Thanksgiving, shown to the right, indicate that most of the Lower 48 has so far avoided harsh winter conditions. In the picture, areas shaded in yellow and red have been relatively warm, and the small pockets of blue have been likewise cold.

Spring-like temperatures have instead been unusually common across much of the country this month, particularly in the Northeast. It’s been at or above 50°F five times in Albany, NY so far this month, twice in Burlington, VT, thirteen times in D.C., and seven times in Boston (with a few 60s thrown in for good measure!).

Ice fishermen in northern Minnesota are battling open lakes, while residents in Wisconsin and in the nearby Great Lakes States are going through the mildest, most snow-free December in years. White Christmas in Minneapolis? Forget about it.

The latest snowfall map shows how just how much bare ground currently occupies the country.


Comparing snowing depths between December 2010 and December 2011 (NOAA/NOHRSC)

This year snow covers 26 percent of the country compared to 48 percent at the same time last year. Consider the following lackluster season-to-date snowfall totals in these northern cities: Boston 1”, Fargo 1.2”, Chicago 1.7”, Syracuse 1.7”, and Green Bay 2.2”

Although a couple of cold fronts will move through the northern tier between now and Christmas, the weather maps thereafter through the New Year’s holiday are lining up to once again show impressive warmth east of the Rockies.


A forecast of the jet stream in about 10 days. (NOAA/ESRL)
The global circulation will then feature strong high altitude westerly winds over the Pacific Basin, which will blast mild air into much of the Lower 48. The first beneficiaries of the unseasonable warmth will be in the Plains, with anomalies in the +10° to +20°F range from North Dakota to Kansas in the couple of days either side of New Years. Around that time, the jet stream flow (black arrow) is expected to look similar to that shown in the image to the right.

With no upper-level blocking expected over the Western Hemisphere to force cold air south, the mild bursts in the Plains should reach the East Coast without too much difficulty.


Temperature forecasts for the Jan/Feb/Mar period from (a) NCEP/CFS forecast model, (b) UKMET ensemble mean system, (c) IRI probability model

Temperature departures from normal during La Nina Winter months. Yellows and blues indicate warm and cold regions, respectively, relative to the 1971-2000 average. (NOAA/ESRL)
As we move forward into early 2012, forecasts from some of the seasonal prediction models for January, February, and March (shown above, where reds indicate warm conditions expected and blues cold) suggest that mild weekly temperature outlooks, like the one expected to finish out December, will be repeated.

And with these prognoses in mind, in the larger context, our winter just might end up looking similar to that offered by the baseline La Nina composite (to the right).

By  |  02:11 PM ET, 12/20/2011

Categories:  Latest, U.S. Weather

 
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