Carvers Gap

As for Mammoth...their webcams are awesome. I dropped a link for their cams on the mountain. They range from 8000' to 11000'. We stayed at 9000' this past summer when we were out there. It is crazy to see everything buried now. The ground was bare two days ago - they had almost no snow below 9500'. Very late season for them. Colorado restorts have bare ground. But...it is easy to see how the Donner party got caught. People were hiking up until two days ago in the 10,000' range...today, you would be stuck. The 6z AIGEFS lent a bit of support to the 0z GEM - it doubled its colder members since 0z. We probably are going to have to look at ensemble members in order to sort the cold fronts out for early January. The mean will continue to be skewed until the last minute I think. https://www.mammothmountain.com/on-the-mountain/mammoth-webcam/woolly-cam

The GFS IMHO continues to be a bit of an outlier as it forms and breaks down the NAO rapidly. I can’t find another model doing that. I can’t remember which model handles the NAO better. Who know? It might be right. The GEM is another adamant outlier outlier with its solution. I would guess it continues to trend towards a NE cold shot vs Deep South. But it has a good habit of finding cold fronts, albeit too intense with its solutions. The Euro looks like good middle ground - for now. I would not be surprised to see models trend colder after a warming trend over night. We have entered that 5-7 day window where things get lost. Also, it would not be surprising if models were simply too quick with the cold. I am noticing a trend to send the cold on Jan 5 instead of 2nd….even the 8th. Models are bouncing between those dates. Remember in late November that modeling had the cold, lost it, and then brought it back. I would not be surprised if we see something similar now. Been kind of a weird year with model biases and feedback. With the exception of the GFS, other modeling has the NAO. So, a great sign that it is still present. I think it is the Euro which eliminates the Aleutian high late in its run. Either way, Merry Christmas to all of you! Have a great day!!!

LOL. That is a great line. I always forget about mountain torque events in Asia. I am assuming this is good or us?

Just looking at the 18z EuroAIFS....that is a pretty good look. It is wild to see the Jan 2 cold front trend today. I think we see several cold fronts forced south and east. That seems like it has slider or clipper potential. But with modeling bouncing around right now.....I hope today is the beginning of the ship being steadied, ie we get a fairly predictable pattern.

I have been wanting to post that GEM map all day. We were doing Christmas with some of my family...I definitely was sneaking a peak at models. But my 12z model deep dive...just now happening. There is an interesting demarcation point after the 5th...does it warm up and we get a heavy rain event as Holston posted? Or does end up frozen(not at those levels)??? I tend to think the cold hangs around, but that is an educated guess and by no means fact.

The very definition as an outlier, but it deserves its moment since it is inside o 240. Departures from normal....That would include -11F IMBY. I have to look at chinook maps for a couple of weeks on modeling. So, humor me...haha.

I have found that the Euro coupled with the GEPS(Canadian ensemble) has been decent this winter. When the two are singing the same song...good thing. When the GFS starts to trend towards them...better thing. The GEM only goes out to 240, so I kind of use the GEPS to see where it might have gone if it went past 300 hours at the deterministic level. Both get to a pretty similar place. BTW, the ensembles have moved quite a lot over the past 48 hours. Right now(rightly or wrongly), I don't trust any model which breaks the NAO down too quickly. Unrelated, it just kind of seems like about the time the NAO makes its exit...the EPO/PNA is gonna pop. That has been a pattern for several winters. NE TN folks have generally not benefitted from this, but with the cold pool so strong...I have to think the cold doesn't get held up at the Plateau or even the Apps.

Some great trends on modeling for the past week or so....still a tough pattern to model. I like @John1122's analog discussion above about 1982. It was one of only two Tenn winters which I missed while living in winter purgatory - Orlando, Florida. I read the newspaper articles about the ice storm, and about Tennessee beating Alabama during the World's Fair. I will say that it got crazy cold during those winters in Orland and wiped out many orange groves that were never replanted.

The 18z GFS find the cold air mass. All...winter...long -> so far. It has almost 50 degree changes(colder) over the GLs. Trending quickly towards what the GEM has had for days. The 18z AIGFS is on board. Honestly, there are so many cold fronts modeled...I have no idea how many there are. Dec 29, Jan 2, Jan 5, Jan 8?.

Now, merge that with the 12z GEM...and we are in business!!!

Sorry, we have been traveling for most of the day.... It has been very right for the 29-30th event...scored the coup. The 18z AIGFS has the Jan 1-2 cold front. The run-to-run for the 18z GFS is MUCH colder. Do I think it gets below zero without snow? Unlikely as the GEM is often too cold. But it ofter correctly sees cold fronts during winter when other models do not - just add back a few degrees for the cold bias. The 18z AIGFS is basically the 12z GEM but just not on steroids...one cold front after another.

Record lows. Seems to be an outlier at 12z, but…it caught the Dec 29th front first. Teens below zero.

The 12z GEM would shatter some records. Crazy run. A few places would have all time records at risk.

The 12z CMC and GFS in a bit of a model battle for Jan 1. The 12z has snow and below zero temps. My money is on the Canadian.

After a super quick skimming of models. The 0z Euro and 0z GEM are cold beginning sometime around Dec 28-29. The GFS really does not like the idea of the Jan 2 cold front...but sends one a few days later. Some of the AIFS models agree w/ the GFS...but for now, I am riding with the coldest models. Why? We have seen a tendency for models to miss or under-do cold fronts. I may try to update 500 here in a sec. That update was pretty much surface focused. As for snow? I have to think one or more of these really cold fronts is going to produce winter precip. It is worth remembering that models often lose systems in the the day 5-7 range...only to find them again, and they restrengthen. We may have short lead times on fronts which bring snow with cold fronts.

Fun with maps...the 18z GFS. We should see these types of runs given the potential for HL blocking. There are gonna be WILD swings as exemplified by the r-2-r map below.

Shiver me timbers. Trough drops into the East and holds. Slider present. NW flow present.

Nice run of the 18z GFS.....

Here are the WxBell maps at 342 from 12z. -75.4 is the coldest I could find. I have the 2m map, and for kicks and giggles, the real feel. I know there has been some discussion of the WxBell algorithm being colder than other models.

Thanks, man. I am finishing up some Christmas shopping so feel free! I am looking at them right now…Large scale changes.

Just looking at the cold in the Canadian front range and prairies across modeling at 12z...it sure looks like "when" not "if" that comes roaring into the Lower US. Modeling appears be working out which front is going to carry it. I would think some snow along the incoming front(whichever turns out to be strongest) seems like an increasing possibility. I think the GFS had -75F at some point late in the run (Yukon). Likely that is feedback, but if it isn't...we may challenge the NA record at some point during January.

The 12z GFS and GEPS ensembles have finally broken towards the deterministic camp...bout time.

The 12z suite looks reasonably consistent w/ the exception of the 12z GFS which for whatever reason sometimes completely loses the NAO on random runs. The 12z AIGFS looks about right. So, we are just gonna sub out the 12z GFS and grab the sixth guy off the bench.

Two, back-2-back cold fronts appear possible between Dec 28 and Jan4. If recent model history trends hold...that second front might be colder than what is modeled(well, except for the GDPS which brought it). The Canadian is likely too cold, but it looks like it might be about to score the coup for the Dec 28th run - most models have trended colder and if memory serves me correctly...it caught that first cold front before any other model(maybe the Euro Weeklies as well). Will models back off the intensity of the cold like they did in early December? I keep asking myself that, and then I remember this is a late December and early January air mass which is BN over western Canada. It is possible that the fronts are under modeled outside of seven days. The Music City Bowl is trending colder....oof.

Some bitterly cold runs overnight for the end of the year and beginning of the New Year. We are gonna get June and January within about 48 hours of each other. LR ext (weeklies) modeling has started to pick up on an EPO ridge towards the end of January. The CFSv2, Euro Weeklies, and CFSv2 seasonals have it. My guess could be sometime around the last week of January. The current pattern appears to be classic "C-FYAO" pattern, otherwise knows as a chinook - then freeze your tail off.