It’s Christmas and I’m not likely to greet many visitors on the Twelve Mile Circle today. Nonetheless I thought I’d post something quirky but topical for those of you who did decided to spend some time on the web today between attending church, opening presents, and pursuing holiday cheer.
We’re having one of those rather rare events in Northern Virginia, a true White Christmas. It doesn’t happen very often, and in fact I can’t remember the last time it did, but we have snow on the ground on Christmas day. Here is the evidence.
Well, actually I took this yesterday evening, Christmas Eve. However it’s still dark outside so this will have to suffice. Trust me, the snow did not melt overnight. We’re supposed to have lots of cold rain this afternoon so it may not last much longer though.
I started wondering about the probability of a White Christmas and, unbelievably, there is actually a Wikipedia page devoted to this very topic. They define a White Christmas as any one with snow on the ground. In other words it doesn’t actually have to snow on Christmas day if unmelted snow from a prior event remains on the ground. I also love that in the United Kingdom, "for the purposes of betting, a Christmas is considered ‘white’ if a single snow flake is observed falling onto the roof of the London Weather Centre in the 24 hours of 25 December, even without a perceivable quantity of snow." I’m not sure why I found that so amusing.
The page includes a chart of probabilities for several cities in the United States, Canada and the United Kingdom. It even links to a great map published by the National Weather Service showing White Christmas probabilities throughout the Lower 48. This is my new favorite map for the week.
SOURCE: National Weather Service Weather Forecast Office – St. Louis
I learned that my hometown has an annual probability of about 13%, so it’s an unusual phenomenon but not nearly as rare as I imagined. It’s on a par with Vancouver, BC and Bradford, England.
Now go spend some time with your family.