December 2025 Short/Medium Range Forecast Thread

[Golf757075]

17 minutes ago, Carvers Gap said:

Dabbling a bit w/ models this morning, the 6z GFS comes pretty close to erasing the standing ridge at the surface.  One cold front after another.  The Euro and CMC are less enthused, but as we've seen, that can change.  The interesting thing this AM is a the TPV paying a visit to New England, and we get a backdoor cold front from it.  That has been on several model runs.  Been a while since we have seen an air mass strong enough to seep down the western slopes of the Apps(from the East).

Carver, you can see LC is trying to be optimistic in his weather america newsletter in the extended range. I hope he is correct. 

[Carvers Gap]

The 12z GFS again almost wipes out the weeks long AN temps regime.   For portions of E TN, we are normal to below for the last ten days of the run!

[Carvers Gap]

The GFS has had a sensitive habit of being able to identify cold before other models.  It is absolutely lit at 12z.

[Carvers Gap]

The 12z GFS is exhibit A in what happens when the trough doesn’t feedback over the NW.

[Matthew70]

MJO for the win 

 

Carver you’ve been all over this.  Gawx has also.

[John1122]

This continues to be so much like a warmer version of Dec 1983. The roller coaster temps, the light snow events with most precip falling as rain during warm ups. 1984 was a great Jan and Feb. Hopefully that is similar as well.

[Daniel Boone]

32 minutes ago, John1122 said:

This continues to be so much like a warmer version of Dec 1983. The roller coaster temps, the light snow events with most precip falling as rain during warm ups. 1984 was a great Jan and Feb. Hopefully that is similar as well.

1983-84 was below average Snowfall here and at KTRI. Had one bonafide Snowstorm in January. 6 inches. Another more scattered banded one where just east of Pennington gap got 5 inches while Pennington only an inch.. Other than that mainly a couple dustings to an inch. February had some very warm days in the 70's . March had one Storm with thunder snow but was rain snow mixed below 2000 feet.

[Carvers Gap]

3 hours ago, Matthew70 said:

MJO for the win 

 

Carver you’ve been all over this.  Gawx has also.

We need ensembles of flip…at least one. 

[beavis1729]

35 minutes ago, John1122 said:

This continues to be so much like a warmer version of Dec 1983. The roller coaster temps, the light snow events with most precip falling as rain during warm ups. 1984 was a great Jan and Feb. Hopefully that is similar as well.

Right on. Even though it’s good to see the models trend a bit colder (relatively speaking) in the 7-14 day range, we really need to get out of this obnoxious chinook pattern. Besides the fact that the warm air is always lurking to the west, it’s an incredibly dry pattern/flow since it blocks any formation of low pressure systems and moisture return.

I can’t count how many times on the operational runs, day after day, where it shows nearly zero precipitation over a 2-week period in the mountain west and plains. While it has generally maintained cold overall temperatures in these parts (at least so far), it’s a very dry and boring pattern. If I lived in Denver or SD, I would be tearing my hair out since it has felt like extended Fall forever. 

Hopefully something will shake up the pattern soon. We need a -AO. 

[Daniel Boone]

3 minutes ago, Carvers Gap said:

We need ensembles of flip…at least one. 

Yeah, if they don't the Warmanista Drums will continue to beat loud.

[Carvers Gap]

Really, early December is not snowy IMBY.   Sometimes, yes.  I have sat through many Christmas parades without barely needing a coat.

Normally, the last of my leaves haven’t fallen until late December - that tree drives me nuts.  All of my leaves have fallen this year.  

To be clear, we actually aren’t in the chinook pattern - yet.  Let’s see how much of that materializes.  The GFS will sometimes lead the way(albeit too quickly sometimes) in finding more cold.  Again, we have been dealing with model feedback errors IMHO and still are.   I think some type of warmup is nearly certain.  
 

I mean it has to warm up, right?  I have been BN almost every day this month.   Again, I need a few warm days. 

[Carvers Gap]

4 minutes ago, Daniel Boone said:

Yeah, if they don't the Warmanista Drums will continue to beat loud.

I don’t worry to much about that really.   This warmup almost certainly is going have some cold shots embedded.  If it keeps eroding, it may become a base cold pattern with warmups.  LOL

[Daniel Boone]

1 minute ago, Carvers Gap said:

I don’t worry to much about that really.   This warmup almost certainly is going have some cold shots embedded.  If it keeps eroding, it may become a base cold pattern with warmups.  LOL

Yep. If that occurs it'll be a pretty good indication of a pretty solid, great Winter imo.

[Carvers Gap]

There is also a part of me that wonders if modeling might not actually correct until inside of d10.  The December 20th cold front is fierce as modeled by the 18z GFS.  It has steadily gotten colder with each run.  I think the time frame monitor after that is the 22-23rd, and then maybe another right after Christmas -a back and forth pattern. 

Ensembles still haven't caught up regarding the 20th likelihood.

[beavis1729]

15 minutes ago, Carvers Gap said:

Really, early December is not snowy IMBY.   Sometimes, yes.  I have sat through many Christmas parades without barely needing a coat.

Normally, the last of my leaves haven’t fallen until late December - that tree drives me nuts.  All of my leaves have fallen this year.  

To be clear, we actually aren’t in the chinook pattern - yet.  Let’s see how much of that materializes.  The GFS will sometimes lead the way(albeit too quickly sometimes) in finding more cold.  Again, we have been dealing with model feedback errors IMHO and still are.   I think some type of warmup is nearly certain.  
 

I mean it has to warm up, right?  I have been BN almost every day this month.   Again, I need a few warm days. 

Agree that we haven’t really experienced the chinook ourselves yet, but the problem is the chinook existing out west in the first place. We need that ridge to move further west and become more meridional, to allow moisture-laden lows to develop. Otherwise, it’s dry and boring NW flow, which can be ok if you get hit by a clipper or two…but there’s always a warm risk nearby since the ridge isn’t far away. I like seeing the cold drop down to the Rockies, with the associated upslope snows…because then that cold usually oozes over here and is longer lasting, and often enables overrunning events. Just my preference based on gut feel and observation over the years, not necessarily very scientific. 
 

Of course, La Niña does tend to lead to the current situation more often than not, so it’s not too surprising. 

As always, great discussion in this sub-forum. 

[Carvers Gap]

9 minutes ago, Daniel Boone said:

Yep. If that occurs it'll be a pretty good indication of a pretty solid, great Winter imo.

For whatever reason, deterministic global models are having a very difficult time seeing cold fronts in the d10-15 range.  I think that is feedback(infinite loop stuff).  The chinook looks plausible and is a pretty normal phenomenon in my book.  The cold fronts pushing it back make a lot of sense as well.  I doubt that pattern is very stable as it requires a lot of amplification to sustain that type of back and forth.  

I just read LC's writeup from last night.  He is firm with his last 1/3 of January and most of Feb being cold.  To me that is a 95-96 type of analog.  But it fights winters which return with some fight - lots of analogs for those.  If the QBO wasn't negative, I would be more solemn.  I suspect we see the NAO fire, and as we know, the lead time on the NAO firing is very short.  

[Carvers Gap]

3 minutes ago, beavis1729 said:

Agree that we haven’t really experienced the chinook ourselves yet, but the problem is the chinook existing out west in the first place. We need that ridge to move further west and become more meridional, to allow moisture-laden lows to develop. Otherwise, it’s dry and boring NW flow, which can be ok if you get hit by a clipper or two…but there’s always a warm risk nearby since the ridge isn’t far away. I like seeing the cold drop down to the Rockies, with the associated upslope snows…because then that cold usually oozes over here and is longer lasting, and often enables overrunning events. Just my preference based on gut feel and observation over the years, not necessarily very scientific. 
 

Of course, La Niña does tend to lead to the current situation more often than not, so it’s not too surprising. 

As always, great discussion in this sub-forum. 

Great observations.  I appreciate your input as always!  

[Carvers Gap]

The 18z GFS does indeed find a Christmas Eve cold front.  Chinook-then-cold front pattern in place.  I actually don't mind that. That is a far better option than the standing ridge(which had rain into almost the Hudson Bay).  It will be interesting to see if it intensifies that 24th cold front with time.  Originally, it had an anafront on that day.  Of course, it has also had sever as well!  LOL

[Daniel Boone]

7 minutes ago, Carvers Gap said:

For whatever reason, deterministic global models are having a very difficult time seeing cold fronts in the d10-15 range.  I think that is feedback(infinite loop stuff).  The chinook looks plausible and is a pretty normal phenomenon in my book.  The cold fronts pushing it back make a lot of sense as well.  I doubt that pattern is very stable as it requires a lot of amplification to sustain that type of back and forth.  

I just read LC's writeup from last night.  He is firm with his last 1/3 of January and most of Feb being cold.  To me that is a 95-96 type of analog.  But it fights winters which return with some fight - lots of analogs for those.  If the QBO wasn't negative, I would be more solemn.  I suspect we see the NAO fire, and as we know, the lead time on the NAO firing is very short.  

Yeah, Webb I think it was commented today of how the deep trough this weekend should speed up the development of the -NAO. Someone posted it on the SE Sub.

[Daniel Boone]

[Carvers Gap]

I think as soon as a model spins up a low over the Canadian Rockies, sends it SW to where is spins off the CA Coast until it strengthens anomalously, and then dies out...has to be tossed right at the point.  The 18z GFS makes a lot of sense until it does that at 210.  Those solutions haven't been materializing.  When the feedback occurs, it spins up a deep trough in the eastern Pac(which originates in Canada!) and that deepens the AN heights over the EC and ensuing Chinook.  Those western Canadian coastal lows are going to get kicked eastward - just how it goes in real life "most" of the time.

I think that problem is over cooking the ensembles.

[Carvers Gap]

1 minute ago, Daniel Boone said:

Yep.  Get rid of that feedback over the Pac NW, the vortices kick eastward, and deepen.  For whatever reason, models are having a very difficult time (past 5-6 weeks) with infinite vortices over the West Coast.  That error is rendering modeling almost useless after hour 200...not that it is super accurate after that during normal times.

@John1122got me into watching Mammoth's snow cams during winter.  I follow a bunch of their pages after the Carver Gap family visit over the summer.  That place is beautiful at all times of the year.  Anyway, they are stuck under that western ridge.  

[Carvers Gap]

31 minutes ago, beavis1729 said:

Agree that we haven’t really experienced the chinook ourselves yet, but the problem is the chinook existing out west in the first place. We need that ridge to move further west and become more meridional, to allow moisture-laden lows to develop. Otherwise, it’s dry and boring NW flow, which can be ok if you get hit by a clipper or two…but there’s always a warm risk nearby since the ridge isn’t far away. I like seeing the cold drop down to the Rockies, with the associated upslope snows…because then that cold usually oozes over here and is longer lasting, and often enables overrunning events. Just my preference based on gut feel and observation over the years, not necessarily very scientific. 
 

Of course, La Niña does tend to lead to the current situation more often than not, so it’s not too surprising. 

As always, great discussion in this sub-forum. 

And be sure to keep posting!  Great to have our input...I meant to add that.

[housemtnTN]

Whooeeeee it's just plain cold out there!

[John1122]

2 hours ago, Daniel Boone said:

1983-84 was below average Snowfall here and at KTRI. Had one bonafide Snowstorm in January. 6 inches. Another more scattered banded one where just east of Pennington gap got 5 inches while Pennington only an inch.. Other than that mainly a couple dustings to an inch. February had some very warm days in the 70's . March had one Storm with thunder snow but was rain snow mixed below 2000 feet.

That's surprising to me. We had a 3 inch, 5 inch and 8 inch event in January and some -10s on multiple days. Another 7 inch event in early February with a -8 after it. 

[Daniel Boone]

1 hour ago, John1122 said:

That's surprising to me. We had a 3 inch, 5 inch and 8 inch event in January and some -10s on multiple days. Another 7 inch event in early February with a -8 after it. 

Here's data from national and State perspective. It's just Temperature. As you can see the Winter, Dec, Jan and Feb averaged slightly below normal. February alone was slightly above. Colder the further west in Southern Plains. I used to have the Data for Pennington. They've changed their Format for Stations Data so will have to find and look it up, also KTRIS. I used to have my own but lost it unfortunately while relocating.

 https://www.ncei.noaa.gov/access/monitoring/climate-at-a-glance/statewide/mapping/110/tavg/198402/3/rank

[John1122]

16 minutes ago, Daniel Boone said:

Here's data from national and State perspective. It's just Temperature. As you can see the Winter, Dec, Jan and Feb averaged slightly below normal. February alone was slightly above. Colder the further west in Southern Plains. I used to have the Data for Pennington. They've changed their Format for Stations Data so will have to find and look it up, also KTRIS. I used to have my own but lost it unfortunately while relocating.

 https://www.ncei.noaa.gov/access/monitoring/climate-at-a-glance/statewide/mapping/110/tavg/198402/3/rank

The official record for Pennington Gap shows 2 events, a 3 and 4 inch event two days later. No idea if it's accurate or not. Shows them on the 16th and 18th. 

The cold front passage was one for the books. It was 63 here one day and had fallen to 1 the next day at midnight. 

[Daniel Boone]

Here's Pennington. It was recorded at the Water Plant right on the banks of Powell River so, doesn't do Pennington gap itself justice really.

https://www.ncei.noaa.gov/access/past-weather/Pennington gap VA

[John1122]

3 minutes ago, Daniel Boone said:

Here's Pennington. It was recorded at the Water Plant right on the banks of Powell River so, doesn't do Pennington gap itself justice really.

https://www.ncei.noaa.gov/access/past-weather/Pennington gap VA

This is the 2nd snow in Pennington Gap in January 84. There is a 3 inch two days before. 

 

 

[Daniel Boone]

3 minutes ago, John1122 said:

The official record for Pennington Gap shows 2 events, a 3 and 4 inch event two days later. No idea if it's accurate or not. Shows them on the 16th and 18th. 

The cold front passage was one for the books. It was 63 here one day and had fallen to 1 the next day at midnight. 

Yeah. I see you found it. Yeah, that would have been the 2 I recall although Pennington itself got 6 from the first one. I don't recall the Feb. One's being what is shows but could of been at that location. I was thinking more 70s in Feb but apparently it was a long stretch of upper 60s and a 70 there. As you can see snowfall was below average. Average in Pennington then was 19.7" as I recall.