Carvers Gap

Not a ton to add this morning. The 0z Euro is by the far the most aggressive model in moving to a look which would deliver cold in the Lower 48 with original from the Arctic. As John noted, models are bouncing around. I originally just took that to be them dialing in a cold shot. I tend to agree that we are probably seeing a pattern change of some sort and of a duration TBD. The CFSv2 is what I hope we transition to, but is by no means a certainty. The MJO certainly appears to be poised to take a trip through the cold phases. Will it happen? Time will tell. If this is true, modeling is going to switch to a pretty cold look. If it is not, it will stay warm. It is worth noting that ensembles now "see" the cold where before they had a suspiciously stagnant patter. Obviously, they smooth things out....but still. If the MJO is correct, I am suspicious of any model which reverts to the big ridge in the East ad nauseam. I would suggest the pattern will be bouts of severe cold followed by extreme warmth until the pattern switches the cold to out West after mid-winter. I could easily be wrong. Let's put it this way, if I saw a model which was cold in the LR but the MJO was rotating into warm phases, I would be suspicious. The opposite is also true. Plenty can still go wrong, but to me it looks like LR modeling does not reflect the outcome that their own MJOs are depicting. To close and beat a dead horse simultaneously, if the MJO is right...we get cold for longer than a week. If the MJO is wrong, the West gets very cold for many weeks.

For sure. An east based -NAO will often retrograde to the west, especially with the warming which just occurred at high latitude. Keep the fires burning. See you all in the morning.

That is mega block on the 0z. I will reference John's post above. I think models are sensing a relatively substantial change after the 20th. Probably tough to know exactly where the chips fall at this range. His posts perfectly states what is potentially going on with modeling. The 0z GFS run is a textbook block. I am not worried about the features at our latitude at this stage in the game. Get that kind of block into place...that is what we are looking for. That would likely deliver very cold air into much of the Lower 48. It is backing off the 21st as a start date. Maybe it is a bit too fast. Maybe it is up to the old trick of pushing cold air back. Key is the block. Get that and let everything else fall into place.

Thing is....IF the -NAO gets established, it is very stubborn in moving. Last winter, modeling erroneously tried breaking down that feature. So key features on maps today: 1. Double block: Some form of AK/Aleutians block couple with a block near Greenland. Aleutian highs are not uncommon during La Ninas. They are normally deal breakers, but for some reason they also show up in cold analogs even without Pac help. 2. PERSISTENT southeast ridge. 3. Periodic extreme bouts of cold and warmth. All of that fits very nicely into La Nina climatology. If it is real, we should have some chances.

The 18z GEFS ensembles have a whopper of a -NAO. So, now we are beginning to see ensembles "see" the possibility for colder solutions in the LR.

The official ale of the TN Valley sub-forum?

Been windy and rainy today. Much needed rain has fallen for most of the afternoon. Leaves are finally off the trees for the most part.

Well, we have been waiting for the ensembles to jump on board. The 12z GEFS....that is quite a change in the LR compared to just a couple of days ago. Big trough late in the run.

Again, well said and thanks!

Yeah, well said. Any guesses which way this heads?

That probably verified out at 30-35 mph stuff thankfully. I think the winds must have pulled-up just far enough off the ground, and that spared us. You could year it, just never made it to the ground.

Bought to drive into it! Thanks. Literally just finished running/biking.

If you really just need a lift this morning, take a look at the 6z CFSv2 control at 500. Enjoy those. You don't see that type of blocking every day on modeling.

First off, thoughts and prayers are with those affected by the severe storms and tornadoes last night in western areas of our forum and in other sub-forums. Secondly, great discussion by everyone both in the severe thread and in this one. Really hope the look in the 6z GFS continues, especially long term. That is how you exit the warm pattern and maintain a winter one for a couple of weeks. Not sure that happens, but the MJO would suggest the cold might hang on longer than expected. Ensembles finally have the trough around the 21st. That leads me to believe they are likely missing other amplifications. As for the snow, I like that look. No idea if it actually occurs, but both the Euro and GFS have something similar. If the cold front is strong, that possibility exists. As the trough enters the eastern US and leaves, that is the first window. Real question then becomes whether a second shot of cold pinwheels in. Some modeling drops it west, while others drop it into the nation's mid-section and scoot it eastward. The GFS, as it did early last season, has the hot hand right now until the Euro takes the throne as the winter pattern stabilizes. The CFSv2, though likely was a bit overdone, may score a bit of a coup if it gets cold prior to Christmas as it had the cold first. Again, not my favorite model, but worth noting it has a warm-up after Christmas at 6z, and then another cold shot during early January. So, I will keep it short for this morning.

I think the SSW has to be embedded in modeling somewhere as the high latitude blocking showing up seems indicative of that. But beware, I have seen SSW fails and then modeling flip back warm OR the cold just dumps somewhere entirely different than originally modeled(could be better or worse). We talked about volatility a week or so ago. Very few things more volatile than an SSW showing up in LR modeling. Literally nothing after the split is likely right. Cohen is smart. I haven't read any of his stuff this winter. I quite twittering about four years ago, so I don't see a lot of what is on social media. I probably should do that more, but just don't for whatever reason. I follow Cosgrove on FB and that is about it....and I do this. Feel free to share Judah's stuff though. I may go catch his blog this evening now that you mention it. I do like Webber and HM though. Strong Twitter game for them. Our mets in this region are the most accurate though. Snow in MBY can be from sliders, but our sliders have to turn the corner a bit in NE TN or Kingsport gets shafted. Flow has to back for the most part. Now JC and Bristol do just fine. Bit of a rain shadow in Kingsport. Our biggest snows are normally a trajectory from SW to NE for the snow axis. Our biggest snows often tap the GOM and/or Atlantic. I have found that big snows in DC usually involve lighter amounts here. Middle and western forum areas often require different ingredients though not always. Last year is a great example as middle and western forum areas got hammered...nada here. Best snows here occurs on Arctic boundaries which have an axis which runs the Apps or SLP through the Carolinas which run from roughly Mobile and inside Savannah. You all do better when the low cuts up the eastern valley - which sucks for us! LOL. Chattanooga folks have multiple rain shadows, get the warm nose, and deal with system trending north whenever the opportunity presents. Bama and Mississippi have done ok in recent years - I think. Ah, and the dreaded dry slot in eastern areas is a bear.

Yeah, very different circumstance to get you snow vs MBY in many cases. The EPS now has the pre-Christmas trough. That is a legit window now I think. PNA spikes positive temporarily for that model on the Euro. We don't need weeks on end of a great pattern, just need a window where it can occur. Today is the first I have seen ensembles move off their spots. Operationals are so different, that something had to give. I generally don't expect snow around my neck of the woods until January or February. We can get it earlier as we have had two great pre-Christmas snows(after going decades without those), but the norm is a six week window from Jan 1 to the middle of February. So anything right now is a bonus. If that 50/50 low is legit, that is important for the eastern half of the forum area.

When is the last time we looked at 12z suite and are like, "Wow, the Euro looked better than the GFS?" Been a couple of weeks, but that is a great looking pattern. Ridge off the west coast popping an albeit likely temporary PNA ridge which sharpens the downstream trough. Then a 50/50ish low is parked in the right spot with energy in the southern jet timed with the northern stream. Lovely look, but ain't no way that is locked in at that range. The great thing even though that is unlikely? The pattern isn't benign.

To clarify...how you draw up a major EC storm. Again, that probably isn't right but that 50/50 has been showing up on multiple runs of multiple models. Just need timing for something to come along behind it with enough spacing.

Posted about the same time you did. Probably isn't right at that range, but that is absolutely how you draw it up.

Post 1: My takeaway from the 12z run is the Pacific (the irony, right?) actually is the driver for colder weather on this run. No idea if true. The Euro at 0z was slower with the MJO and the pattern was slower...but with a similar progression. The GFS is faster in getting the MJO in winter phases, and it shows on this run. I don't have a preference in terms of accuracy at this point. I do have a preference in terms of winter wx!!! Forgot to post the above...so will just post both posts in this one. Post 2: Well, the Euro doubles down on a double block with the NAO strong negative. Looks remarkably like the CMC. Now, I think what modeling are seeing are increasing chances for cold in the East during the last ten days of the month, and possibly into early January if we are luck. Almost all modeling returns to the western trough after that though. Then I would guess that we see another week or two of warm weather followed by another loading of cold which surges eastward. That kind of looks like the pattern for winter and looks remarkably similar to last winter. Good pattern for those in the western 2/3 of the state if that is indeed the pattern. Fun thing to watch. If that NAO forms, I am seeing a low get forced into the NAO block. It slows that low just north of Nova Scotia. That is a recipe for a big storm as it would suppress the flow and force a storm to climb the coast slowly and then stall. Maybe a 50/50 low? Timing appears to be off right now with so few systems in the pattern, but if one were to get in the pattern....look out.

Impressive Alaskan block setting up shop right before Christmas on the 12z GFS run.

Cosgrove noted in a post about a week ago to keep an eye on GOA lows. If they ever move southwest into the Pacific, it sets the stage for the EPO to pop and allow cold air to rush into the Lower 48. That is what is happening in this run.

Pretty impressive run by the 12z GFS unfolding after d9. Long way out there, but that is 17-18 level EPO stuff there if memory serves me correctly. Late December in mid-January. Super dry but incredibly cold with single digits for nearly a week straight for lows with no snow on the ground. Not that cold so far on the run...just looking at the direct path from the Arctic southward.

Thanks! Looks like an EPO ridge creeping towards the WC. That is the same general look as other models, but a bit slower in its evolution which doesn't surprise me given the Euro's tendencies. The breakdown of ridge pattern over the East(even if just temporarily) is what I am looking for evidence of.

Holston, do you have the control for d10-15l?