The flip is coming. Remember the rubber band theory, if you stretch the pattern too far in one direction it will snap back. There has been plenty of cold this Fall and a friend of mine told me the pond hockey conditions are epic. I’m glad that the conditions are epic for some people. The snowmaking conditions are also epic, if you have snow guns…
The original Winter forecast I had was a slow start to the Winter with a dry December and then gangbuster cold and snow in January and February. Now that we are halfway through December I am anxiously looking to see if my January theory will verify. Most of my forecast from the Fall was analogging past moderate La Nina Winter in a cold PDO. Now it’s time to look at the teleconnections to see if they are headed in the right direction.
We have been in the positive AO and PNA pattern here for the past month as you can see above on the tracking for those two teleconnections. Of course we want to see the opposite to get the trough going here down the West Coast. A simplified explanation is when there is a positive AO (Arctic Oscillation) there is lower pressure over the Arctic spinning the jetstream from West to East and holding the cold Arctic air in. When we flip to a negative AO higher pressure builds in over the Arctic disrupting the jetstream and allowing the cold to come South.
The AO has been falling consistently from its strongly positive point a the beginning of the month. I am expecting that to continue into January. There is also stratospheric warming beginning to happen near the Bering Straight. The stratosphere is the layer of the atmosphere above the troposphere that we live in down here. Alot of the time the warmer air at the surface is rising and pushing up on the Stratosphere squeezing it and creating less thickness which causing cooling. So the stratosphere is colder.
During a stratospheric warming event the stratosphere warms and expands pushing down on the troposphere underneath creating less thickness and cooling the troposphere. That warming in the stratosphere is forecasted to coninue to push towards the Arctic as we head towards January. That will cause height rises and higher pressure over the Arctic and and the AO to get negative. And with the stratopheric warming the air coming South will be even colder.
How does this relate to snow? Well with the cold PDO in the Pacific the thinking is that this Arctic air will come into the West first as we go into January pushing the trough down the West Coast. The ridge builds over Alaska replacing the trough over the past month which should push the jet stream South in the Pacific. This is what we saw happen last year when the AO went negative. The combination of the Arctic cold with the jetstream feeding into it would create the kind of January that I am thinking we could have.
This pattern will take a few weeks to develop though. Meanwhile we still have the ridge in the Eastern Pacfic keeping us dry through the weekend. There will be another shot of cold coming down from the North as the Pacific ridge retrogrades back enough to let a storm into the Pacific NW next Wednesday. We’ll have to watch how far that can push South, but it’s not a big snow producer so probably some light snow showers at best.
The models are showing the ridge retrograding again Christmas weekend possibly letting a quick hitting little storm bring in some light snowfall for Christmas. It’s the week after Christmas that it looks like the Pacific NW will start to get hammered with storms as low pressure sets further East in the Gulf of Alaksa and the ridge off the coast begins to flatten. That is a good sign because then we just need the jetstream to shift further down the Coast.
Hopefully that is where the Arctic plunge comes into play to start the New Year. Since we know what to look for it’s just watching for the models to pick up on it. Last Night’s GFS did showing this for New Year’s.
Wouldn’t that be a great way to start the New Year? So now we just need to watch and hopefully this continues to show up on the models over the next 2 weeks. Stay tuned….BA
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