Carvers Gap

I think there are some likely differences getting worked out in modeling. There should be cold pushing further East with an MJO phase 7. Ensembles are still pretty rock solid though. But if the models are going to crack, operationals will crack first.

The 12z GFS has a minor, northwest flow event for favored areas next weekend as well - meaning snow showers with minor accumulations on northwest facing slopes.

@jaxjagman, looks you called it with the cold shot next weekend. 12z GFS/GEFS has it and so does the Euro at 12z. I think this is a great example(if it verifies) of why modeling that looks wall-to-wall warm(or cold) is highly suspicious. Makes me wonder if there is a model input problem in terms of data.

The 12th-19th on the 12z GFS is now BN.

Yal'll we are going to have to get our act together if we are going to have a prolonged warm-up! 12z Euro with a true winter time air mass plunging into the East late in the run. HUGE grains of salt, but that is why I am skittish right now with modeling. Mercy, that is cold - some BN anomalies of 15-20 degrees.

12z CMC has winter weather centered on the 8th in areas on the northern and central Plateau, southeast Kentucky, and southwest Virginia. The Euro had a similar solution but was slightly north.

Jeff is the guru with angular momentum stuff. I admittedly look at not as often as I should. For me, some things in the LR don't quite add up. That said, there are some Nina's which were very warm winters. I highly doubt we go 12 weeks without some chances. Biggest concern right now is the dry pattern. I have generally found that winters with few chances often have very long periods where it doesn't have any precip. That means that an unfavorable temp pattern combined with drought makes it super difficult to sync cold air and infrequent precip. So, we need the frequency of precip to increase in addition to a more favorable temp pattern in the LR. It is really dry IMBY. That needs to change. As for where the pattern begins. I have always felt that because the weather pattern is a circle of sorts, it is hard to tell what causes what. SSTs are generally a great place. However, mountain torque is an under discussed driver(maybe the Urals?). Snow cover does matter. Sea ice numbers across the North Pole matter. I would suspect dust from the Sahara probably has some influence. And on and on.... But I generally agree that Eastern Asia and the Pacific are big drivers. Jax and Jeff look at those regions much more than I do, and know way more than me regarding those regions. Jax has a website that is pretty cool which correlates Bering Sea 500 heights with our regions. High latitude blocking is also important - reference to the SSW discussions. Just really looking for the driver each winter. I generally have found that when we are talking about the MJO in this forum, that the pattern has gone to crap! LOL. Right now, the MJO is the driver. That could change. My rule of thumb is the winter pattern begins to show itself around the third or fourth week of December. I do suspect the November pattern will repeat at some point. Get us some thunder in the mountains, and we know the change is coming. Going to enjoy running in some nice weather. Those November low temps were kicking my tail, man. LOL. It was cold in the morning here!!!!

Agree, Jax. Probably more likely severe than wintry but who knows. Just looking through model ensembles. The 12z EPS late in the run is trying to bring a ridge into the GOA(also found on the control run as well, especially the control run). Maybe a -EPO develops after that? 10th-20th looks pretty well set though as Jax mentions the 11-12th may hold some surprises in terms of the 500 pattern. Get a ridge in the GOA, and the western trough is either going to be very sharp or forced to kick eastward. So after the 20th, could be a continuation of a western trough or a ridge out West could develop for a time.

Crazy looking ice storm on the 12z CMC for the western half of the state around 144. Likely a one off, but impressive run nonetheless.

Very possible. Seems like that area may have had some snow that we didn't have in NE TN. We have family in Mo-town.

The 12z CMC is now showing a similar break(like the Euro yesterday) from continuity. The MJO is now almost universally in phase 7 in the medium to LR which is a cold signal west of the Apps (warm for January though). At 144 the CMC has a severe ice storm for western North Carolina. Interesting this is the timeframe which was showing up on modeling a few days ago and then went poof! Probably a one-off, but that CMC run is not warm. Details embedded within patterns are what matter. Beware when cracks start to show in modeling, especially with the MJO showing high amplitude into phase 7 on some modeling.

The cold snap of 17-18 isn't spoken about much as it produce very little snow and bitterly cold temps. It occurred at the end of December and went to mid-January. That was pretty much it for that winter if I remember correctly. Would not surprise me to see a similar event. If that cold spell had not straddled two months, it would have created a ridiculously cold anomaly for a month. That cold shot is hidden buried in monthly climatology by means which were warmer on the front and back end of that cold snap. That cold snap was preceded by very warm tempt, almost 15 degree departures during a few of the days prior. The rivers here in NE TN (which didn't have dams on them and warmer generator flows) froze almost solid. I remember seeing squirrels walking across creeks which were frozen solid but nearly clear ice due to lack of snow. The squirrel looked as curious as me when it walked out there. This reminds me a lot of that winter. If we had any precip at all, would have been more memorable than it was.

Good post. Will be interesting to see if the MJO sorts itself out during the next couple of days. WxBell has had some good articles about it - D'Aleo's, as I mentioned yesterday, discussion was stellar. The SSW potential is there, meaning sudden warming is modeled in the stratosphere. I think the warmth Dec 10-20th is legit. I think the anomalies will be warm enough to make December as they will override and BN days. After Christmas, all bets are off. Lots of conflicting signals out there. And yes, as we previously spoke in this thread, ridges that connect into high latitudes from low latitudes are often like bringing a jack hammer into a China shop regarding what happens after that. My guess would be that cold is going going to press into the western forum area after the 20th. Will go back and look at trends in a bit. CFSv2 is definitely interesting. Could just be a blip and/or the model just a wicked cold bias...Modeling the next few days will be interesting to watch.

To clarify.....that November turned out super cold!!! LOL. Models were locked on warm. Looked like a slam dunk, and bam! They reversed course. May very well have been a La Niña year. Happy first day of met winter, everyone!

As the phrase goes, time will tell.

Normally, I would toss the Euro. I remember years ago that I was trying to convince John that November was going to be warm. Every model had it, especially the Euro...until it cracked in one run. So, I have learned my lesson. I tend to question modeling which doesn’t show at least some variation. That November Euro would then waffle around for a few days, until it finally flipped. The CPC MJO data is trending to 7 with some 8 showing in the individual ensembles. D’Aleo had a great article today on the MJO. Basically said the BN SSTs in the 7, 8, and 1 regions (La Nina) are not allowing waves to propagate into colder regions. Said this is why models are sending the MJO into 7 and stalling or circling back to 6. So the big question is does it stall in phase 7 or loop back to 6? It may well be that we see some loops from 6-7 and back in a wash-rinse-repeat cycle. If so, the pattern will be more transient than models have depicted. I am super suspicious of the wall-to-wall warmer look. Runs against a big cluster of climatology. So, we will see if the Euro is a one-off. Should see it bounce around some of it is legit. It would take very little to move the needle towards cold. The -QBO is a surprise this winter and will have to be dealt with at some point. We usually get our share of winter here at some point.

Sitting the school car line, but just wanted to state that the 12z Euro is quite the break from continuity from d5-10.

Hoping we see some of that rain. We are far, far from flooding problems IMBY. The Euro Weeklies from Monday were bleak in that regard. Hopefully as La Nina improves during the next 4-6 months, that will get better. If we get under the return flow from the Bermuda High(meant as a joke...kind of), maybe we can get some rain.

November finished -3.1 for the month. That is a stout departure from normal. Can't tell what the rainfall departure(very dry) is at the moment, but it is likely significant.

NE TN and the Plateau have a tad more wiggle room(different formula) than most in the forum area. The mountains here have already received snow - without blocking or a favorable MJO if I remember correctly. Still, we have some winters which were goose eggs. I think we get our chances. Nobody knows at this point.

And while we are on the topic of the MJO, there is still not a definitive trend on its loop into phase 7. In general, looks like it takes a turn into phase 7. Whether it loops back into 6 is a question. Whether it loops into 7, back into 6, and back into 7(hence a loop) is a question. However, I would not rule out a high amplitude turn into a colder phase 7 later in December.

Agree we are very likely in for some prolonged, very warm December weather after the 10th. However, the GFS has pretty substantial warming at 10mb and has consistently shown this for several days. Whether it can split the SPV, now that is another question entirely. I see a temporary displacement into separate regions before coming back together. However, by my definition, that is an SSW(sudden stratospheric warming event for new folks) - I did check the definition before posting this. Last winter we saw several times where the strat warmed, and it looked like it would knock the TPV off its game and did not. Finally, we saw a massive discharge of cold directly south into the nation's mid-section later in winter. I actually consider it a good thing for the SPV to get disrupted early. Now, glass half empty, one could say there is an SSW but the actually TPV is pretty tightly wound. I think we are seeing the top of the polar vortex disrupted, but it is not propagating down to the surface at this point.

And I should add, that if I saw modeling wall-to-wall cold, I would not trust it. Same rule applies for modeling today. A few years back, we had an SSW event during early February. Majority of spring predictions were quite warm. Pretty sure we didn't actually feel spring temps until mid April that year as winter was essentially felt during much of March. Again and not to beat a dead horse, most of the non-winters in E TN are a result of strong El Ninos and a few strong La Ninas thrown in for good measure. The coldest temps I have seen occurred during weak La Ninas and often had very little lead time in terms of forecasting. Always kind of a bummer to see warm temps prognosticated during the run-up to Christmas, but until the last few years(where we have had early season snows), December was a "no go" IMBY for snow. So, not overly concerned at this point with mild December temps. I don't think the base winter pattern is even close to showing itself yet. My non-winter comment originates from the idea that a warm-start to La Nina sometimes foreshadows warm winters, but if one looks at John's data above, there is a cluster of years where the cold didn't arrive until mid-winter or later. It is worth repeating that each year is its own analog.

My ideas during June had a seasonal to BN month of December with January and February being AN w/ BN snowfall(but more than last year). I think all bets are off right now. I "think" I remember correctly that during a handful of weak Nina winters that the overall pattern was not MJO driven. The MJO has been a huge driver of late, and I expect that to continue. However, I don't have all of my eggs in that basket. Second year, weak La Nina's generally have strong climatology which supports strong to severe cold shots even if the overall pattern for the winter is base warm. That was my thinking in June and still is now. The cold shot may not fit perfectly in the month of December. Models this morning are pretty warm for most of the Lower 48 not name Washington state -very zonal. Long way to go as meteorological winter doesn't even start until tomorrow. We have 14 weeks IMBY until things generally break for spring. I am sure lots of unpredictability and volatility awaits. As with any winter, surprises are a near certainty.

After Dec 10th, looks like some warm weather(above to much above is the question at the moment) is highly likely. Models have been persistent with this look. The Weeklies are SER in perpetuity(relentless on that run). I think my idea of an early start to winter (which I put out in maybe June) is headed for bust city. I think January and February have a good chance at verifying. That said, Jan may have a chance at seasonal if the cold is delayed. Although unlikely, I do think a non-winter is possible if the front end of winter is warm. Weak Ninas tend to deliver cold which models are generally blind to at range. So, I think we see 1-2 severe cold shots. Right now the MJO and high latitude blocking are a problem - bad Atlantic and bad Pacific set-ups. The strat warm is a MAJOR wild card. If the SSW occurs from Dec10-15, we could see the first incoming shots of cold into the lower 48 about 20 days or so after that....Cosgrove has a good timeline with that which is sometime after Christmas to the first week of January. So, the Weeklies are likely missing that shot of cold. However, if the SSW doesn't verify, we may be in for a long stretch of warm weather. That is surprising to me, but welcome to modeling chaos - it ain't always predictable. LOL. Huge grains of salt. Volatile pattern, but models seem to be leaning warm during the past 48 hours. Big ridge possible between the 10-20th of December. Would not surprise me to see us in the upper 60s and into the 70s IMBY.