December 2025 Short/Medium Range Forecast Thread

[*Flash*]

I think the January thaw can be overly used sometimes, almost in almanac-y fashion. Even the best winters had their patented patterns relax a time or two; granted, I get how a transition into pause can be unsettling. Apart from present timing, I'm not bummed about a reload due to its necessity and how much we've historically benefited from them. Assuming the upcoming warm spell is overhyped, I could see monthly temps verifying close to average for most, maybe a little above average for west/middle TN. 

Also, I agree with the idea we'll flip cold at some point in January. May not be seasonal climax level but perhaps the start of a stairstep into glory. I know for me, times like these latch my hopes to analogs. For instance, if you like second half loaded winters, our latitude is a place to be as we've seen plenty of them the past decade (I.e. 2014-15 and 2020-21). Those examples saw some gnashing of teeth in the first half before things went gangbusters in the second. Not to suggest this winter is like those winters or anything we've seen the past decade. Certainly, this year feels unique already with our closest saving grace being on the Atlantic side, not the Pacific. Go back and review past winter threads and you'll see how the PNA/WPO/EPO were highly discussed along with the MJO. Per Michael Scott, oh, how the turned tables. 

Whatever transpires in the short term, let the record show I don't ask for much but amplification, volatility, and any west-based retrograding on those strat/Atlantic teleconnections. Winters with trackable systems within multi-week ebb and flows are my favorite. 

[beavis1729]

Speaking for myself on the chinook discussion, I didn’t intend to imply that it would directly affect us with warmth for a long period of time. The problem, in my mind, is the existence of the chinook pattern itself, even though it has really only caused warmth in MT, CO, WY, NE, SD. This has been going on for several weeks. Places like Denver, Cheyenne, and Rapid City have essentially had no winter so far, and unfortunately that looks to continue for the rest of the month. 

Joe Bastardi, or perhaps a different met, has a saying about “the angle of the cold”. In a chinook pattern, the angle of the cold is wrong for us, for two reasons. First, even when it does stay cold here, it’s very dry and boring due to NW flow. Second, the warmth is always lurking, because we’re on the far western edge of the cold airmass. So, any minor change in the flow quickly makes it warmer here. That happened last week in my neck of the woods, where a couple of good early season snowfalls melted away because the warmth out west pivoted over here…even though it only lasted for a few days. 

The point of all this is that, to me, it’s a much better pattern for all of us when there is no chinook at all. I like to see highs come down into the western plains, creating upslope snow in MT/WY/CO, then the cold eventually trickles east and lasts for awhile. Basically, I’m describing a -EPO from a more “on the ground” perspective. 

I just think the current pattern (starting around 12/5) has been very obnoxious, and unfortunately it looks to continue for 10 more days. Definitely good to see some light at the end of the tunnel, and it can’t come soon enough. 

[Carvers Gap]

AIGFS is available on WxBell as of today....new product from the NWS and Co.   The NWS version has the AI-GFS, AI-GEFS, AI-Hybrid(includes current GFS which is combined with the AI model).

NOAA has launched a groundbreaking new suite of operational, artificial intelligence (AI)-driven global weather prediction models, marking a significant advancement in forecast speed, efficiency, and accuracy. The models will provide forecasters with faster delivery of more accurate guidance, while using a fraction of computational resources.

AI-driven global weather models

[beavis1729]

11 minutes ago, Carvers Gap said:

AIGFS is available on WxBell as of today....new product from the NWS and Co.

NOAA has launched a groundbreaking new suite of operational, artificial intelligence (AI)-driven global weather prediction models, marking a significant advancement in forecast speed, efficiency, and accuracy. The models will provide forecasters with faster delivery of more accurate guidance, while using a fraction of computational resources.

AI-driven global weather models

Nice find, and I see it listed as an option on Pivotal Weather too. 

[jaxjagman]

Looks like more like the GFS in the long range,anoms are like 30F-AN on NYD

[jaxjagman]

Sure its still a work in progress,post this just to see around New Years if its close to a severe look,cant get cold bring on severe

[Matthew70]

There is winners & losers in any pattern as we all know.  Even with the Chinook here in TN it’s been a cold December so far.  At least it’s felt & looked on some days like a wintry Christmas.  I think I saw where Chicago was off to a great start for snow?  Maybe it was the snowiest in some time?  Even ND has had a lot of snow.  The pattern will change, and there will be winners & losers again with the reshuffle. I just think many have forgotten winter has officially not even started for most.  We’ve been cold enough so far in December to actually have snow showers & dustings for many.  Anytime you get snow in December is a huge bonus.  January is usually dry & cold.  February is the usual timeframe for Middle & West TN to receive snow. Anything in January is a 50/50 shot.  Crazy to think higher odds for here are in February. So it’s warming up some, which I for one hope it hangs around till day after Christmas.  That way I don’t freeze taking down the outside decorations. 

[Golf757075]

1 hour ago, Matthew70 said:

There is winners & losers in any pattern as we all know.  Even with the Chinook here in TN it’s been a cold December so far.  At least it’s felt & looked on some days like a wintry Christmas.  I think I saw where Chicago was off to a great start for snow?  Maybe it was the snowiest in some time?  Even ND has had a lot of snow.  The pattern will change, and there will be winners & losers again with the reshuffle. I just think many have forgotten winter has officially not even started for most.  We’ve been cold enough so far in December to actually have snow showers & dustings for many.  Anytime you get snow in December is a huge bonus.  January is usually dry & cold.  February is the usual timeframe for Middle & West TN to receive snow. Anything in January is a 50/50 shot.  Crazy to think higher odds for here are in February. So it’s warming up some, which I for one hope it hangs around till day after Christmas.  That way I don’t freeze taking down the outside decorations. 

Here in jackson we haven't seen any snow or ice yet. I hated thar we had too much nw flow, but that's how it is sometimes. Hoping mother nature will throw a little winter weather sometime in the next few months

[John1122]

The ridge/trough orientation has just sucked for basically the entire forum. Especially the west side. It's been cold and mostly dry. We got clipped by a couple of clippers in the East.

If the ridge had been oriented into a +PNA configuration, those clippers that buried the Midwest to Virginia would have been rolling across Tennessee. Northern Kentucky has gotten hit a lot. Louisville Kentucky already has about a foot in the  first 15 days of met winter. With a +PNA that would have had that active northern stream, which is common in La Nina, over our forum area. 

[Golf757075]

41 minutes ago, John1122 said:

The ridge/trough orientation has just sucked for basically the entire forum. Especially the west side. It's been cold and mostly dry. We got clipped by a couple of clippers in the East.

If the ridge had been oriented into a +PNA configuration, those clippers that buried the Midwest to Virginia would have been rolling across Tennessee. Northern Kentucky has gotten hit a lot. Louisville Kentucky already has about a foot in the  first 15 days of met winter. With a +PNA that would have had that active northern stream, which is common in La Nina, over our forum area. 

We haven't had a clipper in my area in a long time. Many years. 

[John1122]

The Euro bombs Northern half of NC and most of Virginia with a monster New Years snow, due to a clipper that rains on us and goes full Miller B on them, after it develops off the coast it spins in place giving them a mega storm. The GFS looks like it may have been loading up to send something our way by the 3rd. Too far out to take seriously of course, but possibly a sign that the NAO is working a bit and use getting scraps while east of the Apps would fit in with the pattern we've seen as far as precip goes.

[Holston_River_Rambler]

6z GFS shows a similar evolution waaaaayyyyyy out in fantasy land to 0z Euro for NC and southside VA. When people root for NAOs to impact the pattern, that's the sort of thing I want. 

[Holston_River_Rambler]

Interestingly both GFS AI and Euro AI both almost look like ensembles for the same period. Since they are machine learning models using (presumably and I could definitely be wrong) the continuity of typical patterns, I wonder if the AI models skew less amplified in the longer range, since dramatic and amplified events are somewhat rare? Would this make the AI models less useful in the medium to longer ranges until they have ingested more datasets of times where large blocks are "bullying" (quoting griteater) the pattern? How many significant, blocky patterns have wee seen since we started running AI models to give them datasets? I would say not many over the regions depicted below, but don't often look at blocky patterns anywhere else, so there could be some confirmation bias at play. 

 

 

 

 

 

 

[Carvers Gap]

The -NAO is the story if it unfold the way modeling has shown it for the past 48 hours.  I don't think it will mean a trough 100% of the time over the EC, but it "could" force the storm track well south as we have see on overnight runs.  The 0z Euro and now 6z GFS.....what a turn of events.

[Carvers Gap]

There will likely be some model chaos(and even real time chaos) w/ two strong and very opposite teleconnections IF they verify.  The Aleutians Ridge and -NAO are not going to play well together.   I suspect we end up w/ a very similar pattern to what we exited, but maybe with the pattern being forced south of where it was due to the NAO and seasonal climatology.  It seems like the Yukon will be cold and will send cold air southeast into a suppressed storm track.  I do think ridges will roll through between cold shots.  But we roll the dice and take our chances if that is indeed the setup.  Suppressed storm tracks with cold involved...we take.  

The nice thing is that most of the models are eliminating feedback over the Pacific Northwest, and we can see what is a reasonable pattern unfolding.  Infinite Baja lows and Pac NW lows.... I guess the question I have now is if there is feedback w/ the Aleutians low and maybe the NAO?  Those are two other areas where models will sometimes under-do and over-do things.

[nrgjeff]

Clippers are hard to get in southern Tenn. Northeast Tenn can benefit from them. Yeah a clipper can happen in Chinook but it'd be tough to get it down here. GaWx is right about the -NAO which could over-achieve northeast only - prolly more like NE USA.

GaWx is a good follow even though mainly Southeast. Close enough his posts can be relevant here. Then I have to whine about how I miss clipper action growing up near KC. Felt like two storm tracks work, clipper and Colorado/SW low. Here it's gotta be near perfect with little margin for error. Guess that's what makes snow in the South special!

 

[Golf757075]

3 hours ago, Carvers Gap said:

There will likely be some model chaos(and even real time chaos) w/ two strong and very opposite teleconnections IF they verify.  The Aleutians Ridge and -NAO are not going to play well together.   I suspect we end up w/ a very similar pattern to what we exited, but maybe with the pattern being forced south of where it was due to the NAO and seasonal climatology.  It seems like the Yukon will be cold and will send cold air southeast into a suppressed storm track.  I do think ridges will roll through between cold shots.  But we roll the dice and take our chances if that is indeed the setup.  Suppressed storm tracks with cold involved...we take.  

The nice thing is that most of the models are eliminating feedback over the Pacific Northwest, and we can see what is a reasonable pattern unfolding.  Infinite Baja lows and Pac NW lows.... I guess the question I have now is if there is feedback w/ the Aleutians low and maybe the NAO?  Those are two other areas where models will sometimes under-do and over-do things.

Carver, I wished the aleutian ridge would retrograde or shift east and morph into a Alaskan ridge lol. Interesting statement. A guy who is a friend of mine on Facebook, which he does a weather page. He mentioned that the farmers almanac shows a winter storm first week in January for mid south/ tennessee valley. That would be interesting because we had one last January around same time. 

I think unless the nao goes west based, it will benefit east of us, but we shall see. Another case of if the nao will be able to morph from east to west based.

[Daniel Boone]

4 hours ago, Holston_River_Rambler said:

Interestingly both GFS AI and Euro AI both almost look like ensembles for the same period. Since they are machine learning models using (presumably and I could definitely be wrong) the continuity of typical patterns, I wonder if the AI models skew less amplified in the longer range, since dramatic and amplified events are somewhat rare? Would this make the AI models less useful in the medium to longer ranges until they have ingested more datasets of times where large blocks are "bullying" (quoting griteater) the pattern? How many significant, blocky patterns have wee seen since we started running AI models to give them datasets? I would say not many over the regions depicted below, but don't often look at blocky patterns anywhere else, so there could be some confirmation bias at play. 

 

 

 

 

 

 

Been thinking same thing. Looks pretty obvious actually, imo. As with the pattern we've been in, regardless if there might be a difference in evolution or trough axis they'll possibly show a similar outcome in snow forecast and show those area's that's had plenty (Southern Va/Northern NC) getting snow and us rain or just more snow than us. 

  I'm not saying that won't be what happens, particularly with a CAD wedge pattern.

That stuff goes into the Model's (Models ingest System) and since they've not been going long as you alluded to, it makes sense. 

[Daniel Boone]

3 hours ago, nrgjeff said:

Clippers are hard to get in southern Tenn. Northeast Tenn can benefit from them. Yeah a clipper can happen in Chinook but it'd be tough to get it down here. GaWx is right about the -NAO which could over-achieve northeast only - prolly more like NE USA.

GaWx is a good follow even though mainly Southeast. Close enough his posts can be relevant here. Then I have to whine about how I miss clipper action growing up near KC. Felt like two storm tracks work, clipper and Colorado/SW low. Here it's gotta be near perfect with little margin for error. Guess that's what makes snow in the South special!

 

Yeah, Larry is a great Asset to American Weather in pretty much all Aspects. Great guy with a Ton of Research Data and Information along with Meteorological Knowledge and Skill.

[Daniel Boone]

4 hours ago, Carvers Gap said:

There will likely be some model chaos(and even real time chaos) w/ two strong and very opposite teleconnections IF they verify.  The Aleutians Ridge and -NAO are not going to play well together.   I suspect we end up w/ a very similar pattern to what we exited, but maybe with the pattern being forced south of where it was due to the NAO and seasonal climatology.  It seems like the Yukon will be cold and will send cold air southeast into a suppressed storm track.  I do think ridges will roll through between cold shots.  But we roll the dice and take our chances if that is indeed the setup.  Suppressed storm tracks with cold involved...we take.  

The nice thing is that most of the models are eliminating feedback over the Pacific Northwest, and we can see what is a reasonable pattern unfolding.  Infinite Baja lows and Pac NW lows.... I guess the question I have now is if there is feedback w/ the Aleutians low and maybe the NAO?  Those are two other areas where models will sometimes under-do and over-do things.

Yeah. If that AH will scoot over Alaska and bridge to the -NAO . A retrogression west or SW of the GOA Low would then setup a pretty much solid cold Pattern. 

12Z GFS illustrates what you mentioned ; Model Chaos. Rather tricky Pattern for Models to decipher. 

[Carvers Gap]

I just wanted to introduce my new friend...

[Carvers Gap]

And, eh, not terrible...ridging in the Eastern Pac.   I thought it might go to crap after this, but the NAO took a shot of the juice and the EPO fired.

[Carvers Gap]

This is only ten days out...this isn't the Weeklies or 300+.  That sure looked like it was going to slide the trough from the GOA right into the nation's mid-section.  That ridge over the eastern Pac wasn't moving.  

 

[Carvers Gap]

The 0z GDPS probably had the best looks by 240.  Trough in the East, split flow, -NAO...I wasn't gonna post it but might as well.  To me this makes sense IF the NAO is legit.  The 12z GFS is out in the weeds....

[Carvers Gap]

The reason I posted these is to illustrate that sooner or later the NAO is gonna put the squeeze on this pattern.  The NAO is a trump card as is the EPO.  If one is in play, that is a good thing regardless of the MJO phase, etc.  The tendency is for the trough to find its way eastward when the NAO is present on modeling.  The 12z GFS shows what happens when it is late to the party.  The Canadian suite is most definitely the fastest flip.

[Carvers Gap]

50 minutes ago, Daniel Boone said:

Yeah. If that AH will scoot over Alaska and bridge to the -NAO . A retrogression west or SW of the GOA Low would then setup a pretty much solid cold Pattern. 

12Z GFS illustrates what you mentioned ; Model Chaos. Rather tricky Pattern for Models to decipher. 

The 12z GFS has pretty massive feedback issues.  I don't really have a problem w/ a trough off the West Coast - that happens. The 5-7 days of endless vortices spinning up just doesn't make sense.  Just when I thought it had that worked out....it is right back to it.  The 12z GFS really doesn't have a -NAO either.  We need the NAO to establish HL blocking and force the issue I think.  The GFS is just way off on its own by 300.

[Carvers Gap]

2 hours ago, Golf757075 said:

Carver, I wished the aleutian ridge would retrograde or shift east and morph into a Alaskan ridge lol. Interesting statement. A guy who is a friend of mine on Facebook, which he does a weather page. He mentioned that the farmers almanac shows a winter storm first week in January for mid south/ tennessee valley. That would be interesting because we had one last January around same time. 

I think unless the nao goes west based, it will benefit east of us, but we shall see. Another case of if the nao will be able to morph from east to west based.

Unfortunately, the Aleutian Ridge has been a staple of recent past Nina winters - the big red ball on 500 maps.  If forces a Rex block.

Models have a very difficult time "knowing" when it ends - much like the NAO.  I don't think there is a lot of data in that area, and that can be a problem.  It seems like the Aleutian Ridge has a tendency to disappear with little notice, and the trough kicks almost immediately eastward. Those ice and snow storms that middle and west Tenn have experienced occurred when that Aleutians Ridge pattern relaxed.  It seems to me that usually occurs between the first and third weeks of January.  

I know some think the trough retrogrades and does not come back.  If the NAO goes negative, that could balance things out.  We lacked the NAO w/ recent analogs where the trough pulled back, and wouldn't budge.  

There is a lot of uncertainty going forward.  I generally like uncertainty, because that leaves room for crazy weather.  In winter, that could be anything from severe (which I don't like) to winter storms.  

I think the key going forward is the NAO going negative.  It is the ingredient in many EC storms.  That doesn't necessarily help you all just to the west...but it can force sliders in addition to coastals.

[Carvers Gap]

The 12z Euro takes the GDPS/CMC route, and quickly establishes influence by the NAO, but it quickly loses it.  I think modeling at 12z is on the struggle bus(not abnormal) w/ the NAO.  I have seen the NAO absolutely wreck what looked like very nice, consistent patterns.  It is a bull in a China shop.  There is a lot to like about this still frame.  There is a lot to not like about what happens next!  Haha.  But we take this over a chinook any day of the week.  By the end of the run, the Euro looked to resolidify the NAO and swing the big trough east.  Almost all modeling is teasing sending that western trough eastward.  It "could" be too quick, but some the CMC and Euro are about 3-7 days quicker depending on the run.  IF the NAO block is legit, it is going to create more wild solutions like it did at 12z.  If we can get any help from the Pac....then bigger things are on the table.

spell check will be the death of me....

[Golf757075]

11 minutes ago, Carvers Gap said:

The 12z Euro takes the GDPS/CMC route, and quickly establishes influence by the NAO, but it quickly loses it.  I think modeling at 12z is on the struggle bus(not abnormal) w/ the NAO.  I have seen the NAO absolutely wreck what looked like very nice, consistent patterns.  It is a bull in a China shop.  There is a lot to like about this still frame.  There is a lot to not like about what happens next!  Haha.  But we take this over a chinook any day of the week.  By the end of the run, the Euro looked to resolidify the NAO and swing the big trough east.  Almost all modeling is teasing sending that western trough eastward.  It "could" be too quick, but some the CMC and Euro are about 3-7 days quicker depending on the run.  IF the NAO block is legit, it is going to create more wild solutions like it did at 12z.  If we can get any help from the Pac....then bigger things are on the table.

spell check will be the death of me....

Model chaos at its best lol. We do it every winter 

[Carvers Gap]

8 minutes ago, Golf757075 said:

Model chaos at its best lol. We do it every winter 

I like it a lot better than 16 straight days of chinooks on deterministic runs.  LOL.  It might still get warm, but I gotta have room for some surprises.