WHEN IN DOUBT, RUN WITH THE EURO....
I (and many other forecasters) frequently talk about the how the skill scores of the EURO are superior to the GFS. You can see below the how the model has the best verification scores compared to numerous other models around the globe. At 48 hours the EURO (ECMWF) is already outperforming the GFS (NCEP models) and at 168 hours is all by itself leading the pack. The proof is in the pudding!
So when I see a run of the GFS operational that shows a 500mb chart December 19th that looks like this, I go really?
Considering the teleconnections I'm seeing on the EURO which include the cold signals of a negative AO, EPO, and WPO, I can't buy that much ridging into the Midwest. Then there's the MJO, look where the EURO seasonal ensemble shows it tracking...right into phases 7, 8, and 1 between now and January 5th
Once again those phases are the holy grail for cold in the Midwest. Here's the phase correlations for temperature and precipitation. Phases 7 and 8 are punched in December. See their analogs below.
Phase 1: Phase 1 is achieved in January. Look for that analog below.
The deck is stacked for cold and what the GFS operational shows makes no sense. Hard to take it seriously, especially when it shows snowfall that looks like this. Minnesota and Wisconsin getting hammered. It's even at odds with its own ensembles! Extremely unlikely.
Going to the EURO I see that it fits its teleconnections and MJO forecasts. The 500mb pattern below for December 19th is what I would expect to see. Compare the EURO ensembles below to the GFS above. The west coast ridge is more in line with my thinking.
The temperature departure on the EURO is flat out frigid.
It has 850 temps that are down to -33 in northern Minnesota. That is some big ticket cold if it materializes in the days just before Christmas.
You can also see without the warm air advection the GFS depicts, it has much lighter 15 day snow totals. None of those 20" amounts the GFS put out in southern Minnesota. This looks far more believable.
So there you have it, a bunch of reasons why the EURO will probably win this model fight.
One last thing I will mention and that's the fact we will see a couple days of moderation later this weekend. In fact, highs could reach the low 40s in parts of my area Sunday. The reason why is the next batch of polar air is getting set to dive into the Midwest. Ahead of it warm advection and SW winds should send out a bubble of warmth. It's only temporary as 20s return by next Tuesday. Roll weather...TS