It has been on the mild side for much of November and December along and east of the Mississippi river but some signs of possible change could lead to a burst of cold that may hold for a bit during the first week or January. One of these factors is the NAO (North Atlantic Oscilation) which is forecast to finally go negative. If that holds true it would be the first negative tilt in the NAO since mid October.
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| NAO Forecast |
What this means is that a better opportunity for a trough to develop in the Eastern U.S. ad that would allow for cold to sink out of the Polar region. In fact, the ECMWF (European) model is picking up on this and its possible ramification. Below is an image of its forecast for the morning of Tuesday, January 3, 2012. Notice in the upper left quadrant of the image that a deep trough develops behind a strong upper level piece of energy across the center of the nation.
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| ECMWF Forecast (obtained from Penn State Ewall) |
Additional forecasts for the next several following days show this trough translating east and recharging through January 6. This would bring the season's coldest shot of air into the populated east. It also would likely bring the winter's first widespread snow event.
I will take a closer look at this on Wednesday evenings live weather briefing at 8:30 pm, here at dopplerdale.com
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