On Tuesday I posted about the long range weather pattern that showed signs of changing in a cold and potentially snowy way. That change is appearing more and more likely as our computer models agree in an impressive blast of Arctic air.
Here’s the day 10 Euro Ensemble mean 850 mb temperature. At near -8C on the Connecticut/Massachusetts line that’s quite impressive for a D10 ensemble mean and quite a bit below normal. The pattern is being driven by a large chunk of ridging and above normal heights from northeast Russia through the Bering Strait and Alsska which is effectively dislodging cold from the Arctic.
What makes this even more impressive is the “ridge bridge” that sets up with ridging over the North Atlantic and Greenland effectively connecting with the Ridging over northern Russia. This decapitates the Polar Vortex and allows the cold to spill south. The Arctic Oscillation, which had been strongly positive, is now forecast to dive.
What gives me increased confidence in this actually occurring is the fact both the Euro ensembles and GFS ensembles appear to be on the same page in the North Pacific with a large area of above normal heights and ridging over Alaska.
It’s unclear just how cold and stormy we will get Thanksgiving week and beyond. The first shot of wintry weather may be fairly minor on Saturday as cold high pressure is slow to retreat ahead of an advancing low. This could be a wintry mix to rain kind of deal. Past Saturday the details are fuzzy at best. At this point an extended period of below normal weather is quite possible.