Friday, November 30, 2012

Are You Dreaming of a White Christmas for 2012?

Thanks to a relatively warm and dry fall across a good part of the country, many are convinced that scenes like the one above will be hard to come by this winter...

To that I say, fear not, winter weather and snow lovers:  a major pattern change appears to be shaping up for mid through late December which will likely put down a snow field across a good chunk of the nation - perhaps just in time for many to have that much sought after White Christmas.

December will start out warmer than normal across a good portion of the nation, as indicated by the latest 6-10 day departure from normal temperature forecast from the CPC shown below (valid December 5th-9th):

Meanwhile, bitterly cold air will continue to build up across Alaska and Canada.  Temperatures across much of this region are currently sub-zero, with a large pocket of minus teens and minus 20s in western Canada and eastern Alaska:  

This bitterly cold air will continue to accumulate through the 2nd week of December, before the weight of the airmass combined with increasing jet stream energy from the West begins to break it loose and send it Southeastward into the U.S. in one or more waves.  This will likely result in below normal temperatures across much of the central and eastern two thirds of the country by the 2nd half of the month, similar to the area shown in blue and green on the departure from normal temperature forecast below:

As a result of the cold air intrusion(s) and increasing middle and upper-level energy, the chance of measurable snow will increase across a large portion of the country from North to South beginning around mid-December and continuing through the end of the month, including Christmas time.

The 4 panel image below shows the forecast snow depth from 4 different long range computer forecast models.  Each model forecast is valid for the 5 day period leading up to Christmas (December 20th-25th):

As you can see, 2 of the four computer model solutions suggest that measurable snow could reach as far South as northern Texas by that time period (bottom of the image).  The other 2 forecast the measurable snow to remain in the more "traditional" areas of the central and northern Plains and Midwest into the Northeast (top of the image).  

This is just meant to give an early "heads-up" for everybody, as we still have a lot of time to watch this and things can certainly change, but I don't want winter weather and snow lovers to give up on the prospects of a more active 2nd half of December (which is really when Winter officially starts anyway), which may also lead to a White Christmas for a good chunk of the nation.

So, without further ado, please cue Mr. Bing Crosby...

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