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Don Paul: What are the odds for a White Christmas?

An outlook like this one for December temperatures from the National Weather Service Climate Prediction Center isn’t all that useful when most meteorologists know December is likely to have at least a couple of pattern shifts, starting cold and then warming up. The warmer pattern may end up lasting a few weeks, with a great deal of uncertainty on its longevity and strength.

As you would expect, there is less uncertainty for the first part of the month than for the middle and, of course, the end. So we’ll begin at the beginning. During the first week, colder temperatures will become established in our part of the country, though not as cold as our record Thankgiving Day. The upper air pattern during our weekend warmup shows the warm ridging in the east. With nearly springlike 50s on Sunday along with some rain, snow cover will be in short supply by the beginning of next week.

By late in the week, however, a cold trough will deepening farther east in Canada, allowing modified arctic air to make a comeback.

There is no sign this seasonably cold pattern will be locking in for a long time. As we get into the middle part of the month, a more west-to-east upper air pattern, called a zonal flow, will be flooding much of the lower 48 with Pacific air, cutting off most of the arctic air:

These ensemble “means” of the upper air are a form of smoothed data derived from many individual runs of models. A zonal flow in an ensemble 14 days out can still be interrupted by a strong wave in the flow, shaking things up for a day or two. But for now, the ensembles are bullish on a mid-month warmup. Here is the American/GFS ensemble mean for Dec. 12.

The Canadian ensemble mean is even more aggressive with the the mild, Pacific flow.

The European ensemble mean is in good agreement with the others. Uncertainty increases as we head toward Dec 20-Christmas and the beginning of the new year, as you would expect. Due to the high uncertainty that far out in time, I’m not about to dip my toe into a pool on chances for a White Christmas based on this data. I can show you our climatology over the years.

Buffalo and Western New York, as you can see, have higher probabilities for a White Christmas in climatology than many parts of the country. However, past average climate statistics are not a forecast for THIS year. If that relatively mild zonal/Pacific flow were to continue beyond Dec. 20 all the way out to Christmas, our probabilities for a White Christmas would be well below our average probability.

With the higher confidence on mid-month moderation, the probabilities for much of whatever snow we collect between the 1st and the 11th sticking around are lower. For skiers, the nearer-term good news is it should be cold enough as next week unfolds for good snow-making conditions, even if natural snowfall comes up short. So, I’m optimistic about conditions for next weekend, though sketchy snowfall estimates from models are unimpressive. For example, here is the GFS total snowfall by Dec. 10.

The Canadian is similar.

The newer experimental replacement for the GFS is the snowiest. Last week, it did the best job on the heaviest amounts at high elevations:

This time, even its numbers are more restrained. As of now, it does not appear a mess o’ snow is going to fall during the colder first third of December. There should be several rounds of snow showers, and some chance for limited lake snow toward next weekend, but so far there are no signs of any big time events. So far.

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