Year in and year out there is always an interest across the United States and the world for matter regarding whether or not there is a decent chance of there being a White Christmas. Being as though it is Christmas Day and millions of people living in more than a dozen cities spread across the United States have already experienced a White Christmas here in 2017, it is always interesting to understand more about why the percentages of there actually being a White Christmas varies so much in going from north to south across the nation.
It is important to acknowledge the fact that the verification of there being a White Christmas is contingent upon there being snowfall cover on the ground during the period between Christmas Eve and Christmas Day and/or there being a verification of new snowfall accumulating during that same period of time. More often that not, the reason why the odds of there being a White Christmas is due to the predominant storm track in place across a good portion of the lower 48 states. From year-to-year, this average national storm track position obviously varies based on the influences from various global climatic teleconnections such as the El Nino Southern Oscillation. Having said that, based on the fact that we are currently under the influence of a Central Pacific Ocean-based La Nina event. Thus, the typical storm track position during a typical La Nina Winter is roughly positioned along a track from the Pacific Northwest and southeastward towards the Southeastern United States.
Nonetheless, as with any national climatic tendencies based on trends tied to seasonal climatic variability, there is always subs-seasonal variability associated with where low-pressure systems enter various parts of the contiguous U.S. For instance, over the past 48 to 72 hours, a relatively weak "Alberta Clipper" low-pressure system entered the U.S. and progressed east-southeastward towards the North-Central U.S. before heading towards the interior Northeastern U.S. Upon reaching the greater Mid-Atlantic coastline, the system transferred its energy towards the area just offshore from the Delmarva Peninsula before moving off to the northeast with time. As a result, this system delivered mostly rainfall to the greater NYC metro area. However, more inland locations across New York and up towards New England all witnessed a White Christmas. Hence, areas which typically have less than a 40% chance of witnessing a White Christmas got that and more today in some cases.
It just goes to show that dreams can come true when the atmospheric storm track and timing decides to play along with the hopes and dreams of younger generations who anticipate this time of year all year long.
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©2017 Meteorologist Jordan Rabinowitz