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Don Paul: Winter will relax its icy grip ... temporarily

You wouldn’t know it this week, but after a brutal lake-effect storm Sunday, an early-week widespread snowfall, and then some follow-up lake effect in arctic cold …winter will cut us some slack, beginning next weekend. We’re not headed toward a dramatic warming trend, but we are headed toward seasonable or even slightly-milder-than-average temperatures for a while.

Here is the current upper-air pattern, courtesy Dr. Ryan Maue of weather.us. It features a warm, dry ridge of high pressure over western North America. That ridge forces the polar jet stream to go up and over the ridge and then dive back down into a long wave trough, dragging arctic air into the east from central Canada.

That warm western ridge is also largely responsible for the horrific setup of desert levels of humidity and hot Santa Ana winds in southern California.

By the time we get to the weekend, the western ridge is going to flatten to some extent. Move that mountain out of the way, and some Pacific air can rush in and replace some of the arctic air. Take a look.

That’s not exactly springtime, but the weakening of that ridge will allow temperatures like this, by Sunday and early next week.

(Graphic courtesy of NOAA)

Between now and that moderation, however, here is the European model’s projection of snowfall between Dec. 11 and Dec. 18. Much of the area of heavier snow is tied to our Buffalo Bills' loving pal, lake effect.

Unfortunately, the western ridge will not weaken enough to allow rainfall to reach southern California for more than two weeks, if then. Here is the American GFS depiction for the next 16 days. The GFS is far from foolproof, to put it mildly, but it has the general idea. An interior western U.S. high-pressure ridge will keep the flow offshore there, from the dry desert toward the coast most days. Go this page, then click on the arrow above the map to animate this model and notice what happens when rain approaches southern California:

This is typically when the rainy season gets going. So far, it’s not going anywhere.

Back to Western New York: The relaxation in our wintry pattern will not last all that long. The western ridge will be bulking up again toward Christmas. This re-amplification implies a return to midwinter conditions just in time for Santa to enjoy the ride:

(Graphic courtesy of NOAA)

That lovely map depicts a mean of many runs of the GFS for Christmas morning. Of larger cities, Buffalo has better than most northern cities’ probability for a White Christmas in any given year. Such is our December climatology.

I may regret writing this, but I’d say this year our chances exceed climatology. It’s not a lock, but it’s a pretty good bet. Irving Berlin would be pleased.

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