CAPE

Towards the end of the EPS run a bit of a split flow develops as the NPJ retracts and the western US ridge amplifies- the STJ also links up so there might be a possibility of some energy taking the southern route going forward with colder air in place. Nice jet streak in a decent spot. Looking at h5 there is an indication of pieces of energy in the southern stream flow. NS will be busy but with the -EPO/TPV combo in a Nina that's gonna be a thing.

A legitimate NA (omega) block, amped EPO ridge, and a ridge bridge. Hell yeah. Odds of it verifying...

Some flakes in the air at least, maybe a coating in places. Who would complain about that?

My recollection is we were teased with classic Nino looks and NA blocking on the extended products for months, then ultimately seeing it advertised within a couple weeks on ens guidance when it finally went poof. Regardless, my expectation for the evolving longwave pattern is a significant -EPO developing and persisting for the first 10 days or so of Jan, with the Pacific puke induced Canadian heat ridge evolving into a modest -NAO. Beyond that, we shall see.

But we did see this last year, constantly depicted by guidance in the LR, and it never really materialized. Other variables have influence ofc. Last winter (being a Nino)we didn't have the -EPO. I know some others don't agree, but in a current day Nina that is a key feature imo to bring cold/ flatten the SER tendency. We will need at least some help in the NA to slow/suppress the flow to increase our chances of a wave tracking further south, or a hell of a lot of luck. Hopefully we get a modest -NAO period in conjunction with an EPO ridge- which is what we are seeing at the end of the ens runs/ continuing with the extended guidance. Once the cold is in place, it comes down to wave timing, and maybe we get a little southern stream action as well. Drooling over depicted epic blocking possibilities on LR guidance is a fools errand, as usual, imo. Well timed transient -NAO episodes will have to do the trick, and often do in a Nina when we get moderate snow events.

It was epic is what it was. Proper. It developed early in large part from a retrograding Scandi ridge and persisted. True atmospheric block. Maybe next winter we get the elusive Modoki Nino with blocking, and see how it goes.

I'm rooting for 2009-10 style blocking, but I doubt it happens. Guidance has been depicting a -EPO tendency going back months with the seasonal tools. And its happening. That's the reality. Ofc we don't want a +AO/NAO. But if you go back and look at some of the good snow events of recent Nina years, we did have a transient -NAO in some, which helped. A legit HL block is probably not in the cards this winter, but something bootleg/transient could work. Getting back to the early Jan period, most ens/extended guidance depict a strongly -EPO, with a modestly negative AO/NAO. All these features wax and wane, which is not easily detected on a mean. So as usual, we will need some luck with timing. Also seeing hints of split flow with a bit of a southern stream.

The big 3 global ensembles have a significantly -EPO at the end of their 0z runs. Slightly -AO and NAO. GEFS surface temps still a bit on the warm side but the Euro has about average trending slightly below. Canadian a bit colder.

It's a bit wonky the way it forms and as advertised it doesn't become the classic rex block with a low in the 50-50 position(trough is displaced further out in the N Atlantic). No cold air around until the ridge goes up out west. Lets see how persistent it is as we get colder air in place. If it doesn't block/divert the flow and keep HP locked in to our north with storms tracking underneath then it isn't very useful lol. We have seen this pretty frequently in recent winters.

Its snow on the 12km Other guidance has some precip but mostly rain for our area.

lol NAM Someone should start a thread.

Yeah the EPO ridge is the key to getting cold again. The +heights on the panel from your post are mostly a result of the anomalous warmth that builds across Canada in the days prior. Once the EPO ridge develops and colder air starts to get reestablished, hopefully we see a period with the NAO neutral/slightly negative. The very end of the latest EPS/GEFS hinting at it and the Weeklies are depicting this at least for a time in early Jan. That's probably our first potential window.

A week of above normal isnt a disaster.

Both the GEFS and EPS have high pressure pressing southward along the east coast for much of Christmas week with the last bit of Canadian cold hanging on, while the rest of the continent is overcome by the Pacific onslaught and above normal temps. Lucky us!

Understood. Jan 22 was a pretty good month for a big chunk of our subforum though, not just the eastern part. Again, I think what you are referring to at D15 is essentially something transient that resembles a good pattern- not a Nino like pattern that's going to persist. Take a look at h5 and the North American surface temps on the EPS between Dec 28 and Jan 1. At the end of the run you can see the jet retraction/retrograding NPAC trough and the western ridge start to go up. That is the beginning of scouring out the Pacific air from our source region. Now all the extended products could be wrong- but they continue that pattern progression.

That day 15 look is devoid of cold. Those +heights in the NA are a remnant of the bad pattern leading up to it. We can't snow with that. The pattern needs to progress to the -EPO/TPV combo to bring the cold. The risk is cold and dry, but gotta have the cold. The trough will probably broaden/shift west as the ridge axis does(typical Nina). Keep the EPO ridge and time a wave or 2. That's how we win lately in a Nina. Forget big snow. Forget your 40" climo average. Be content with a few light/ moderate events. Beach chase if there is an offshore bomb.

That's the difference on the latest runs for western areas- the low associated with the weak clipper stays more intact. For eastern areas the inverted trough thing never works out at our latitude, and if some light precip does manage to fall temps are warmish, so probably light rain or maybe a snow tv mix.

That would be a pretty good NA look by traditional standards/ if we looked at it in isolation. Specifically in this case what that panel represents is a step in the transition from the prior Pac puke onslaught with a torched Canada to the pattern being advertised a few days later on the latest EPS weeklies. That is the same look depicted on Jan 1 of the weeklies, and it ends up like this by the 6th-

It is Nino-ish to a degree. Not sure about STJ contribution, but if this look verifies we have a mechanism between the EPO ridge and the stretched TPV for Polar air to chill Canada pretty quickly with cold moving southeastward from there. Maybe after this pattern reset and being further into winter we get better luck with NS wave timing. A little -NAO action certainly would help to slow the flow a bit and hold the cold in instead of exiting stage right as a storm approaches. AO/NAO looks neutral here.

The latest extended products have normal temps back in the east within the first few days of Jan, then colder from there through mid month. Pattern might go more 'classic Nina' by the end of the month, but the -EPO looks to persist into early Feb which should keep the SER on the flat side.

Yeah all the ensembles depict the same general pattern evolution. Canadian is quickest in getting some colder air eastward.

The shortwave energy is sharper and goes more neutral over the last few runs of the GFS. The surface reflection from the weak clipper is also a bit stronger so maybe between it and the developing offshore low we get a bit of moisture transport.

The extended products have been pretty persistent with the idea of a cold period in January. We shall see if we get lucky with coincidence of antecedent cold and a well timed wave.