Haven't done a pattern thread in awhile, but things are aligning pretty well from a teleconnections perspective to establish a colder and possibly stormier than normal pattern for the 2nd half of January and whenever that kind of pattern forms, there is a greater probability of above average snowfall. Have done a bunch of these threads over the years and more often than not they have delivered on increased snowfall for our area (but definitely not every time). As always, I'm not a meteorologist, but when quite a few mets are predicting such a pattern, it's worth paying attention to.
With regard to what the thinking is behind this, there are links to a post by an excellent young met on AmericanWx (brooklynwx99) and a video by WxRisk (DT), below. Essentially, the medium range models are showing a robust ridge forming in the PacNW, coupled with an Aleution upper level low, forcing the polar jet stream up and over that ridge and then spilling SE as a trough drawing cold air from Canada (via Siberia) into the eastern half of the US and then sometimes heading NE driving potential storms towards our area. In the GIF below, from brooklynwx99, you can see the persistent ridge at 500 mbar (mid-level of the atmosphere) near Alaska (in orange) and the persistent resulting trough in the eastern US (in blue).
From a global perspective, the MJO (Madden-Julian Oscillation), a measure of equatorial convection from the Indian Ocean through the Pacific, is what is fueling this jet stream combination above, as the MJO enters phases 8 and then 1. In turn, the "teleconnections" that are favorable for cold/snow in the eastern US are a -NAO, a -AO, a -EPO and a +PNA, all of which are predicted to occur starting by mid-January and lasting through the end of the month (at least). The video, in particular, describes the MJO and the teleconnections in much better detail with excellent graphics, so I won't bother to try to provide more detail here, as I can't do it better than WxRisk did anyway.
In addition, there will likely be a "split flow" with the subropical jet stream being active in sending moisture from the Pacific across the southern US, leading to potential "phasing" of the two jet streams, which is often a key ingredient in major east coast snowstorms - the AmericanWx post describes this in very nice detail with graphics.
The first chance for a signficant storm is about a week from now, with the various global models all showing a winter storm of some sort next Sunday, but differing greatly in the details, such that anything from nada to a significant winter storm is possible. And there are additional signals after that for significant winter storms. Way, way, way too early to predict anything specific for any location, but this is the kind of pattern that needs to be watched closely. So, let's see what happens.
I know some will say, big deal, it usually snows in January, which is true, but this is about potentially getting more snow than usual and a greater probability of a significant snowstorm or two. All through December the pattern was warm and hostile for cold/snow in the eastern US, as we had a persistent ridge in the SE US pumping warm air into our area, so we got no snow at all. This pattern starting changing in early January a bit, but was still not particularly favorable for cold and/or snow and we got nothing until Friday for most of us, while the big storm for VA/DE/MD and SENJ on Monday just shows that it's always possible to get snow in a bad to neutral pattern in winter.
https://www.33andrain.com/topic/204...n-winter-21-22/?do=findComment&comment=299689
