December 25th is fast approaching — but will yours be snow-laden? This map, released by NOAA and the National Climatic Data Center (NCDC), gives the probability of a "White Christmas" across the continental United States.
A White Christmas, according to the NCDC, is one with an inch or more of snow on the ground at 6 A.M. on December 25th. Remember — this is a probability map, not a forecast; meteorologists can really only predict weather a few days ahead of time (and even then, as everyone knows, they can be wrong), so actual conditions two weeks from now could be much different from the percentages and distributions seen here. The probabilities on this map illustrate historical snowfall frequency, and were produced by averaging weather records collected over a thirty year period by close to 10,000 National Weather Service stations. According to NOAA, they should be used as a guide, and show only where a White Christmas is more likely. Here's a slightly different looking representation of the same data, released yesterday by NOAA:
That said, some places are all but certain to receive their share of yuletide snowfall, including Marquette and Sault Ste. Marie, Michigan; Hibbing and International Falls, Minnesota; and Stampede Pass, WA. From a 1995 technical report issued by the NCDC:
Generally, the greatest probabilities lie where they would be expected—over the northern U.S. and in mountainous areas. In defining a 'white Christmas' as having a snow depth of at least 1 inch, the chances are 60% or better over an area including much of the northern Rockies, the northern Great Plains, the Great Lakes area, and most of New England. The chances are less than 20% over most of the southern third of the country excluding the Rockies, along with the Pacific coast.
If you're looking for a more granular breakdown of your region's historical yuletide snowfall, the following sequence of maps depicts snow depth across the continental U.S. for every December 25th for the past decade (via NWS's National Snow Analyses applet):
Those interested in keeping track of North American snowfall in the days leading up to December 25th should check out NOAA's Operational Daily Snow Analysis Charts.
A version of this post appeared in December, 2012.