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Don Paul: Daring to forecast Thanksgiving weather

Don Paul

I’m going to take a shot at travel conditions locally and over a wide area for next Wednesday and Thanksgiving Day, even though we're a week out.

Having scanned extended range model and ensemble guidance, this very preliminary forecast is made possible by the overall pattern I’m seeing and the improved performance of those models and ensembles. If the guidance were “all over the place” (as is frequently the case) and were pointing to the possibility of a major storm system near us, I’d keep my big mouth shut.

Still, I may yet live to regret this decision.

First, let’s look at the overall upper air pattern and progression. You can slow this ensemble loop down if you like as you view it with the control buttons. It basically shows what we call a lower amplitude pattern. That is, there is no deep, sharp trough of low pressure over the Great Lakes as we get to next Wednesday and Thanksgiving. There is no connection to the true polar air over central and northern Canada.

The lower amplitude flow lessens the probability of deep storm systems near us and the probability of extremely cold temperatures.

There is also fairly good agreement on the low probability for extreme cold near us next Wednesday and Thursday. Ensemble agreement is a grand thing. Here is the upper air depiction from the European ensemble. It shows a departing cold trough in blue and an approaching milder ridge aloft in tan:


The American/GEFS ensemble is slower with the cold’s departure, though this model and its ensemble often has a cold bias. Still, it does show the coldest air beginning to move out by Wednesday.

The Canadian GEM ensemble is closer to the faster European ensemble.

What these three ensembles show is the best chance for really wintry temperatures will be in New England and eastern Canada, with more seasonably chilly temperatures developing in the Great Lakes and milder temps in the Midwest and plains.

In actual model output for high temperatures, the American GFS has us in the mid-30s Wednesday, with somewhat milder air poised to our west.

The Canadian GEM tacks on a few degrees Wednesday, but it still has us seasonably cold.

So, no, it’s not going to be a balmy Thanksgiving, but we will be dealing with seasonable chill, not unseasonable cold.

As far as chances for snow, other frozen precipitation, or rain, look at the low probabilities in this computer output from National Weather Service HQ for the biggest traveling day, Wednesday, in our region:

This National Weather Service surface map translates to almost zero chance of significant snow at any major air hub. Atlanta, Chicago and the east coast cities look solid, with no weather-related delays. There could be some rain showers in Houston, Dallas and New Orleans on Wednesday, as well as in the Pacific Northwest.

Later into the weekend, there is at least some sketchy hope for stricken California around Saturday in the Canadian GEM.

Similar hope appears in the new, experimental version of the GFS.

The big, fat caveat for the Saturday, Nov. 24, rain output in two models for California is simply that models have low skill predicting precipitation so far in advance. Temperatures are somewhat more reliable at that time range.

For local travel on Wednesday and Thursday, a few light snow showers can’t be ruled out.

As for actual storms with impact around here, it looks like the only way that might happen is if someone brings up politics at the dinner table.

Talk sports. It’s a little safer.

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