Carvers Gap

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 workout 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. 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.

I will re-respond. Mercy! Cold source. Check.

I found this analog in the d6-10 analogs of CPC. 1-7-94. I could see that being usable. John always has to remind me of that winter. I had to go back and look it up. Sure enough, that winter I had to drive to campus on frozen interstates for about a week. My apartment started leaking as water backed up under the ice. It may be a reach on my part, but that analog makes some sense, and it has fit recent winters. I don't know its ENSO state, but that might be one to think about.

I am gonna tag @John1122in this. His records are easily the best and most uncorrupted that I know of. They are rigorous and have good fidelity to boot(they are his family's for those who don't know). He might be able to shed some light on Maue's thoughts and hopefully chip in some insight. John, I am not asking you to support or criticize RM...just to add some context to the cold forecast in Alaska and in relation to our area.

Nice post. Interesting find by Golf. I keep an off-and-on eye on the coldest modeled mins for North America during the winter. I do that just to monitor how cold our cold source could be. The coldest I can find right now is low -60s. Now, that is pretty cold, but the record is -81 in the Yukon in 1947 according to a quick search. This is not for you, Jed. I know you know this. I am just trying to save a second post. Models have been having crazy amounts of feedback this winter. I think they are vastly overdoing certain features(Baja, NW Pac lows on repeat, western Canada cold?) which causes wild feedback all over the Western Hemisphere. I am not sure why this is happening. I don't know if there is a data ingest problem or programming has been changed/updated across models. Maybe they have a bug? But I have observed some pretty big errors. It reminds me of the 4' of snow forecast for Charlotte one year...and it never materialized. It was feedback which sometimes occurs to the SE of the southern tip of the Apps. Places on the map to watch for feedback...Baja, NW Pac, Aleutians(but not as bad as one would think IMHO), and Greenland. Now, the fun thing about that area of South Carolina which tends to feedback....sometimes it actually has extreme precip events. Think Helene. All of those other places have had extreme events...sometimes I think models go to that extreme due to those data sets. I would guess that Canada is going to be very, very cold this winter. That is a pretty easy guess as it already has been there this season. I think it finds its way south 1-2 times, and that will be plenty for most. Like you, I don't see even 100 year cold up there right now. But we'll see. Not everything is feedback though. I guess maybe the thing that concerns me some is that many of these cold fronts are getting much colder as we get closer to the event - that is kind of unusual. That might be a signal that the air mass up there is strong. We have good snowpack for it to move quickly. I would be more than thrilled to track an all-time great Arctic outbreak w/ lots of snow. I just don't know that we are gonna get much lead time on that... That said, I do think the strength of the cold is currently and is going to be in the future...a problem for modeling this winter. We have had some winters where we get a trough in the East, and there is only Canadian or weak polar air to fill it. This stuff is legit Arctic air. Let's not forget the SSW....we haven't had the cold dive to our side of the planet with that recently. But Russia and/or China have been hammered when that occurs. Sometimes, it does come to our side of the planet. Is this one of our years? Maybe, and there is some evidence to support that but just to early to know. edit: On an interesting note, my daytime highs for the past couple of months have sometimes been well under the point and click forecasts. I am ready for a few days of warm air. I keep waiting on some warm mornings! It was not warm this morning.

Yeah, that is extra special mojo right there.

So far, we have a brand new baby Flash and a Nick Saban connection in this thread. The day just keeps getting better. The point and click below is pretty wild in my book. Is the "thunder in the mountains" rule going to score coming out of this? I am gonna post these here and see how many verify.... My iPhone has my local at 60F on Sunday for a high and then maybe doesn't go above freezing again until Wednesday(not this Weds)!!! The Native Americans noticed Chinooks first in the Pacific NW according to Wikipedia(I did not know this). I am nearly certain the Native Americans of the Plains were thankful for it. In the Plains, chinooks also helped farmers get their cattle through winter. It also allowed for snow to evaporate and dissipate, thus limiting catastrophic snowmelt during spring. It has a purpose. Great article here in this link. https://sheridanmedia.com/news/185207/history-chinook-winds/ It has been scientifically determined that the Chinook wind, falling from mountain to plain is warmed at the rate of about 1–degree for each 180 feet of descent. A fall of 5500 feet from the summit or the Cascade mountains to the wide plateau of the interior will rise the temperature of the wind by about 80 degrees.

Just tagging on to @Matthew70's post...Here is the Euro Weeklies (ensemble) map from a week ago and compared to todays run for December 30th. There is a PNA ridge which is likely just temporary. There is a -NAO whose duration is TBD. The Rex block relaxes. This could easily flip back, but that is big change. Want to guess what caught the trend? The Euro control of all things. The extended version of the deterministic run possibly sniffed out out this cold front at full range(360 hours).

Digging through ensemble members. It looks like there is potential for another strong cold front on Jan6-7 - per GEFS. This looks like a very active pattern coming up in regards to cold. Let's hope some precip can work its way in. I would think clippers and NW flow would be on the table for even norther portions of Gulf States IF that pattern verifies.

I know this is a bunch of posts and my apologies. The 12z para GDPS goes back-to-back w/ cold fronts beginning w/ the 28-29th. We could certainly be cold and dry. That is with precedent. However, the storm track should be suppressed with this. With the return flow behind these fronts, one would think at some point either the cold air doesn't get out of the way(over running WAA) or the warm air doesn't get out of the way. To me, the para GDPS is a logical path forward, but by no means not the only one.

Take a look at the difference in on the ensemble between 18z GEFS yesterday and 12z today...I have been griping about this for weeks. This is for Dec 28-29. There were a few really strong warm air masses embedded in the ensemble mean. They were greatly skewing the mean - even though there were a greater number of colder members included. As we get closer to the event, the anomalously warm air masses are subtracted. And we get this substantial move. Do I still think we see chinooks? Yes, that seems baked in the cake. However, this may we a winter where the colder air masses get colder as reality gets closer. Those are kind of fun winters BTW. We don't get a lot of those. Normally, we see cold air masses moderate as they get closer to reality - Ex A is early December. To be clear, I do want to see a few more runs before declaring the Jan 2-3 cold air mass has legs. If models are flipping this much, they could easily flip right back.