CAPE

It's a little hard to get a sense of it looking at a composite, but a sustained -NAO (and often a quasi-stationary 50-50 low underneath) produces a true "block" in the flow- basically the opposite of a progressive pattern. Along with a favorable storm track and a more sustained eastern trough, it 'forces' a strengthening coastal low to move more slowly to the NE or ENE under the block.

Many here have probably seen this CWG article by Wes from a few winters ago, but for those who have not, it is very good and explains/discusses the roles of the key indices(AO, NAO, EPO, ENSO, etc) and their impacts on cold and snow for the DC area, and includes insightful scatter diagrams. https://www.washingtonpost.com/news/capital-weather-gang/wp/2015/11/12/what-the-different-weather-patterns-might-mean-for-snow-this-winter/

For now I will hang my hat on the CFS weeklies. Starts to shift the long wave pattern around the 20th to a gradient look, then develops a favorable EPO ridge and deep trough in the east into Feb. With a +NAO it would probably feature NW tracking lows followed by cold/dry.

That blocking ridge in the Pac looks legit and stable on the means. At some point the pattern will break down. Hopefully we don't waste most of Jan in the process.

++AO be damned. Indicators schmindicators. We just cant know. We could very well have a MA blizzard by Jan 10!.

The early Jan period has looked like our first best chance of timing something for some frozen for a while now. Several days ago it looked more like the 4th or 5th, now its a bit later. It is pretty much all we got other than hand wringing over the possibility of an awful pattern that may or may not verify going forward. That said, this modest threat still lies outside of 7 days and could easily evaporate or morph into something much different. As currently depicted by the major globals, it is about as good a look as we can expect given the general 500 mb pattern, and one that favors something tracking underneath with some decent cold air in place.

6z GEFS is in for a little something around day 10. Seems to favor southern parts of the region looking at the snow map.

Yeah if that ridge stays parked near the Aleutians it will be a big battle to keep the SE ridge from wrecking hopes and dreams of snow weenies in the MA and SE. Hopefully the 'hints' of NA blocking(yet again) we are seeing on guidance is real, and it would likely take a stout west-based block to do the trick unless something significant changes out west.

One thing we need is some tweakage in the EPO domain. Probably need to lose or shift that trough near Okhotsk.

Speaking of hostile Pac, and for those who like to use the term "blocking", that advertised EPAC ridge near the Aleutians is a monster of a block in the the LR. The GEFS attempts to build some ridging into the NAO domain(EPS not so much) later in the run, .but it would literally take a strong NA block to counter that beast out in the Pacific in order to get lower heights into the eastern US.

Best to just drink more and worry less about the upcoming advertised h5 pattern. Its just not a pretty picture no matter how optimistic you are. Not to say it wont look more favorable in the near future. We all know how this works. Stuff can change pretty quickly.

When does the GFS/GEFS not show big time cold in the long range? I am still looking forward to that Jacksonville blizzard.

Seems like the PV intensity is going to wax and wane this winter. Looks like its going to be on the strong/consolidated side and live up near the pole over the next couple weeks. Hopefully beyond that we see more perturbations with some developing height rises in the high latitudes. It's definitely a tad discouraging seeing all that blue up top going forward on the means, but it is what it is.

Looking through the 0z EPS members, I see 10 or so that have light/moderate frozen for our region between Jan 1 and 7. Not a strong signal, but that period still has potential for some sort of a well timed modest wave to track underneath after a cold front, or a front end slop to rain deal. In this pattern the cold will be fleeting so we will need the usual good timing and luck.

Not sure I agree. There is the tendency for EC/SE ridging showing up on the ensembles in the LR. It's not a stationary/persistent feature on the means, but given the 500 mb pattern being advertised(+AO/+NAO/westward displaced EPAC ridge), it would not be surprising if it ends up more of a fixture than currently depicted.

Both the EPS and GEFS are building heights in the EPO space towards day 15, but it's a bit too far west. There will be a mechanism to get cold air delivery into Canada, but we will probably need to be patient here. Hopefully the -EPO is real, and the long wave pattern progresses eastward. Verbatim the mean trough will be in the western US with a west based EPO ridge, and with a +NAO, there will a tendency for a persistent SE ridge, and a storm track to our NW.

Here is h5 for the first week of Jan from the 0z EPS run. I've seen better lol. 0z GEFS has a bit more ridging out west and normal h5 heights for the east coast for the same period, with lower height anomalies just to the NW over the GLs. Overall colder look.

First week of Jan continues to look active on the GEFS with some cold around. As depicted it could be an interesting period. Fwiw, the snow means the past few runs have looked decent for the window beginning around Jan 3. Given the GFS propensity for overdoing cold in the LR, not getting overly excited about it yet, and the EPS isn't as enthusiastic.

Its gonna be cold after Jan 1. Wonder if DT could advise me on the chances of this verifying. Thinking of heading to J-ville for a chase.

Not gonna see much 50-50 low action with a +NAO. 50-50 highs are going to be more likely. The currently advertised LR h5 pattern is pretty much the inversion of what we want to see. Is it correct? Who knows.

Not pretty. The +AO/+NAO/+EPO trifecta provides literally no mechanism for cold air delivery into the mid latitudes. Hopefully it is a temporary state, or the guidance is currently overstating that look.

Yeah it builds the NAO ridge week 4-5, so who knows how real that is. Looks somewhat positive/neutral before that. Hopefully the EPO ridge gets into a better spot, because I still have my doubts about a sustained NA block, and as you said without it we fight the tendency for SE ridging given the advertised the EPO location verbatim.

Agreed. If the CFS actually has a clue, I would be ok with what it's advertising overall, with an EPO ridge and a mostly neutral AO/NAO look, and a piece of the TPV on our side, although not necessarily in an ideal spot. This look would be acceptable for mid-late Jan:

Beginning right around the new year continues to look potentially active, with at least somewhat colder air in place. 6z GEFS upped the game a bit. First week of Jan has what looks to be multiple waves tracking just to our south. Rolling through the p-type panels for that period is a fun exercise, and it is also reflected on the snowfall mean.

Glancing at the 0z means, looks like straight up blue across the top at h5 in the LR. +EPO/+AO/+NAO. The hints of a building EPO ridge from previous runs are gone for now(or delayed). Despite that, we manage at least seasonable cold, as advertised. Likely some IOD/MJO 'conflicts' still playing into the currently advertised pattern evolution beyond day 10.. The latest CFS weeklies look pretty nice weeks 2-6. Active look week 2, and general cold beyond that with a -EPO, and even hints of a -NAO week 5.