Looking long-term: the odds of a White Christmas
I Christmas is still too far away to have a ‘good’ handle on the forecast, and given the weather pattern expected from next weekend through the end of the month, there’s a lot that can go wrong with a ‘deterministic’ forecast for a single day. Next weekend may start out wet; leftover rain from a slow-moving storm system on Friday may linger into Saturday. Sunday and Christmas Eve look dry for now, but Christmas Day could be cold and…probably dry.
But wait! There’s more…
Three days’ worth of GFS computer model guidance for 06Z Tuesday December 25th (that’s midnight – prime Santa time) shows a decent chance of some precipitation. Several runs have tried to make it snow some. For an event more than ten days in the future, that’s an awfully tough call. We looked at something similar that was forecast for last week over ten days in advance, and it missed pretty badly for our specific location; however, it did get the general idea regionally: snow for some, rain for some. It just could not pinpoint exactly what it would be at your house at a specific time.
It still can’t do that, so if you’re a model-watcher (or if you’d just like to see a little snow at Christmas), be careful of what you read and see on social media!
By the way, the GFS’ chief competitor, the ECMWF, doesn’t bring any snow at all. It does make it cold in time for Christmas Day, though.
So is that a non-answer? Yeah. That’s exactly what it is. There’s no way to ‘know’ this far out, but as we often say, the closer we get the better idea we’ll have.
What are the odds?
Statistical historical probability of a White Christmas does not favor us in Alabama and Tennessee; we’re solidly in the 0-10% chance of any given year.
When asked, I like to say ‘there’s always a chance until there isn’t one.’ In other words, until we know it won’t happen (and there are some times we know for sure), there’s still a chance it could happen.
I think back to Christmas 1989 when we got a ‘surprise’ light snow that started on Christmas Eve and gave us a technically ‘White Christmas’ (barely an inch of snow). There was also the over-performing storm in 2010 that dumped several inches of snow in North Alabama on Christmas Day.
It can happen. It might happen. It’s just not all that likely right now.