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]

8 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. 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.