December 2025 Short/Medium Range Forecast Thread

[Carvers Gap]

The surface pressure anomalies are not bad throughout.

[Matthew70]

It’s amazing how if a model shows a winter storm 15 days out so many will say ah that’s not happening.  Yet when a model shows dry & warm they take it as 100% happening.  
Negativity is rampant in many forums.  
Yeah it sucks having no snow in December but when did December become the only month of winter?  
I missed the memo that says after December winter is over.  
I know for Middle & West TN February has most of the top 10 snows. December is running way below average & we still hear winter is over.  Good gracious.  

[Carvers Gap]

15 minutes ago, Matthew70 said:

It’s amazing how if a model shows a winter storm 15 days out so many will say ah that’s not happening.  Yet when a model shows dry & warm they take it as 100% happening.  
Negativity is rampant in many forums.  
Yeah it sucks having no snow in December but when did December become the only month of winter?  
I missed the memo that says after December winter is over.  
I know for Middle & West TN February has most of the top 10 snows. December is running way below average & we still hear winter is over.  Good gracious.  

And it could end up being warm.  But in the end, it is just something none of us can control.  The thing that will irritate me when tracking winter patterns....a model flip away from a cold, storm pattern.  In this case, the chinook pattern has been well advertised.  What I want to see is that pattern to be muted.  Modeling is apparently going to miss at least two cold fronts...maybe more.  Those fronts are getting colder as reality approaches.  That is a sure tell that modeling is correcting.  There is also a bit of a disconnect between 500 and the surface.  So, interesting times ahead.  Prim climatology is still almost a month away.  And yes, I could use a few warm days just to thaw out.  It has been BN here since Thanksgiving...I need a break from the cold.  You won't hear me say that often!

[beavis1729]

41 minutes ago, Matthew70 said:

It’s amazing how if a model shows a winter storm 15 days out so many will say ah that’s not happening.  Yet when a model shows dry & warm they take it as 100% happening.  
Negativity is rampant in many forums.  
Yeah it sucks having no snow in December but when did December become the only month of winter?  
I missed the memo that says after December winter is over.  
I know for Middle & West TN February has most of the top 10 snows. December is running way below average & we still hear winter is over.  Good gracious.  

All good, and I definitely hear you. Speaking for myself (and possibly many others on the board), I don’t think people are saying that winter is over. People are just sad that winter is taking a break. For those who love winter like myself, we want it to look and feel like winter throughout DJF. Most people like warm weather, and I don’t mind it either…and that’s fine during the other 9 months of the year. I just want DJF to be sacred, especially December due to the short days and holidays…and mild temps during these months (even for a day or two) are annoying to me. I always say it’s more about the look and feel and tenor of the season, as opposed to just chasing a big storm. 

In some ways, it’s analogous to being a sports fan. You want your team to win every game, even though it’s not realistic. When you love something, emotion is more meaningful than logic. And I definitely get the logic piece, since I have a met degree. My career ended up going in a different direction, but it’s still one of my favorite hobbies, mainly driven by the beauty of winter. 

[John1122]

3 hours ago, Holston_River_Rambler said:

That -WPO has got to be one of the most persistent features I've seen on models. Don't take this as an addition to the warm vs cold debate, I'm just struck by how well that Aleutian ridge is holding on. It's not just that there is a ridge there either, but how stout it has been. 

 

 

 

Unfortunately they are notoriously hard to discharge.  On average, they persist for 33 days in winter, but can go longer.  About 60 percent of the time they lead to a split or displacement of the Polar Vortex, and over 95 percent of the time an early AH saw the PV disturbed later in the season.  

A paper I read about them noted that there could be a connection to extreme weather after they break down. They used December '84 as an example. One formed on December 3rd, the PV was disturbed on December 30th, and the AH dissolved on January 4th 1985. 

[John1122]

During that AH period in 1984, we were cold a few days after it formed, had a light snow event, highs in the 20s and single digit lows. Then the rest of December except for a couple of days, was very warm. We were in the 70s a week after the single digits and back in the 70s a few days after Christmas, with plenty of 60s in between. That continued into early January and the AH finally started breaking down and it flipped cold, then it flipped exceptionally cold. 

[beavis1729]

1 minute ago, John1122 said:

During that AH period in 1984, we were cold a few days after it formed, had a light snow event, highs in the 20s and single digit lows. Then the rest of December except for a couple of days, was very warm. We were in the 70s a week after the single digits and back in the 70s a few days after Christmas, with plenty of 60s in between. That continued into early January and the AH finally started breaking down and it flipped cold, then it flipped exceptionally cold. 

Yeah, that was a crazy period. Chicago was 69F on 12/28/1984, then a few weeks later it hit -27F on 1/20/1985 during one of the greatest arctic outbreaks in modern history.

[submariner]

46 minutes ago, beavis1729 said:

All good, and I definitely hear you. Speaking for myself (and possibly many others on the board), I don’t think people are saying that winter is over. People are just sad that winter is taking a break. For those who love winter like myself, we want it to look and feel like winter throughout DJF. Most people like warm weather, and I don’t mind it either…and that’s fine during the other 9 months of the year. I just want DJF to be sacred, especially December due to the short days and holidays…and mild temps during these months (even for a day or two) are annoying to me. I always say it’s more about the look and feel and tenor of the season, as opposed to just chasing a big storm. 

In some ways, it’s analogous to being a sports fan. You want your team to win every game, even though it’s not realistic. When you love something, emotion is more meaningful than logic. And I definitely get the logic piece, since I have a met degree. My career ended up going in a different direction, but it’s still one of my favorite hobbies, mainly driven by the beauty of winter. 

There is a desire, for us winter folks, to have this time of year be like winter. I don't rule anything out (I am just in awe of what you guys know and share) because half the time I'm using AI to decipher your posts. However, I'll just say it. A white Christmas is always nice.

[Golf757075]

1 hour ago, John1122 said:

During that AH period in 1984, we were cold a few days after it formed, had a light snow event, highs in the 20s and single digit lows. Then the rest of December except for a couple of days, was very warm. We were in the 70s a week after the single digits and back in the 70s a few days after Christmas, with plenty of 60s in between. That continued into early January and the AH finally started breaking down and it flipped cold, then it flipped exceptionally cold. 

There was a big SSW event that led to the big cold January through early March in December. Very similar to December 2021 when it was real warm and then flipped colder but not as cold as 1984-85. 

[John1122]

20 minutes ago, Golf757075 said:

There was a big SSW event that led to the big cold January through early March in December. Very similar to December 2021 when it was real warm and then flipped colder but not as cold as 1984-85. 

According to the paper, the Aleutian high contributed to the SSW event on December 30th, 1984.  

[Daniel Boone]

1 hour ago, beavis1729 said:

Yeah, that was a crazy period. Chicago was 69F on 12/28/1984, then a few weeks later it hit -27F on 1/20/1985 during one of the greatest arctic outbreaks in modern history.

Yeah, the most amazing imo was Knoxville hitting -24. -27 at my house west of Pennington gap Va. Couple -30 readings and a -32 reported in rural Wise County near Norton as I recall.

 What did you record there John ?

[Matthew70]

2 hours ago, Carvers Gap said:

And it could end up being warm.  But in the end, it is just something none of us can control.  The thing that will irritate me when tracking winter patterns....a model flip away from a cold, storm pattern.  In this case, the chinook pattern has been well advertised.  What I want to see is that pattern to be muted.  Modeling is apparently going to miss at least two cold fronts...maybe more.  Those fronts are getting colder as reality approaches.  That is a sure tell that modeling is correcting.  There is also a bit of a disconnect between 500 and the surface.  So, interesting times ahead.  Prim climatology is still almost a month away.  And yes, I could use a few warm days just to thaw out.  It has been BN here since Thanksgiving...I need a break from the cold.  You won't hear me say that often!

Well said.  Love learning in this forum.  I had never heard of the chinook effect till here.  Really good stuff!

Thank You!

[Matthew70]

2 hours ago, beavis1729 said:

All good, and I definitely hear you. Speaking for myself (and possibly many others on the board), I don’t think people are saying that winter is over. People are just sad that winter is taking a break. For those who love winter like myself, we want it to look and feel like winter throughout DJF. Most people like warm weather, and I don’t mind it either…and that’s fine during the other 9 months of the year. I just want DJF to be sacred, especially December due to the short days and holidays…and mild temps during these months (even for a day or two) are annoying to me. I always say it’s more about the look and feel and tenor of the season, as opposed to just chasing a big storm. 

In some ways, it’s analogous to being a sports fan. You want your team to win every game, even though it’s not realistic. When you love something, emotion is more meaningful than logic. And I definitely get the logic piece, since I have a met degree. My career ended up going in a different direction, but it’s still one of my favorite hobbies, mainly driven by the beauty of winter. 

Absolutely agree & well said.  Crazy how many of us love winter months.  It’s truly a special time of year.  It’s great smelling the firewood burning in the crisp cool fall.  Nothing like a snow cover under a full moon.  Plus it’s freaking great to have no insects!!!!

Here is to hoping we all get plenty of snow soon!

[Matthew70]

2 hours ago, John1122 said:

Unfortunately they are notoriously hard to discharge.  On average, they persist for 33 days in winter, but can go longer.  About 60 percent of the time they lead to a split or displacement of the Polar Vortex, and over 95 percent of the time an early AH saw the PV disturbed later in the season.  

A paper I read about them noted that there could be a connection to extreme weather after they break down. They used December '84 as an example. One formed on December 3rd, the PV was disturbed on December 30th, and the AH dissolved on January 4th 1985. 

Any idea how many days this -WPO has existed?

[John1122]

55 minutes ago, Daniel Boone said:

Yeah, the most amazing imo was Knoxville hitting -24. -27 at my house west of Pennington gap Va. Couple -30 readings and a -32 reported in rural Wise County near Norton as I recall.

 What did you record there John ?

-28 with 9.5 inches of snow on the ground. -2 high temp. It snowed 4 inches, then snow showers for a couple days, then 8.5 on the 21st. It got up to 37 one of the days or we'd have had 12-13 inches on the ground. That would have probably produced -30s here. 

[Golf757075]

1 hour ago, John1122 said:

According to the paper, the Aleutian high contributed to the SSW event on December 30th, 1984.  

Maybe it will lead to a bigger SSW eventually this winter. That would be nice. It will take alot to beat mid Feb 2021. A week of winter storms

[John1122]

1 hour ago, Matthew70 said:

Any idea how many days this -WPO has existed?

The WPO has been negative through our cold snap since late November. It was deeply negative a couple of days ago, which is one of the reasons we got this big cold snap the last couple of days.  It looks like it goes + in about a week on the GFS and it's positive on Christmas. Which means warm east. It flips back negative towards the end of the run on the GFS.  The aleutian ridge moves east over Alaska and could be working towards a +PNA, but it could be a headfake.

[Carvers Gap]

The 6z GFS, right on cue, again cuts into the chinook look.  The CMC is now on board with this as well.  One thing I am noticing in modeling is that across the board it is greatly modifying the warmth as it draws closer.  We have seen this happen(in reverse) when advertised cold air masses(which are supposed to last for days....modify and are merely a frontal passage.  Right now, the 20th and 22nd look ripe for decent cold fronts. 

Is it possible the deterministic models were to quick in bringing in the chinook and it still may materialize?  Maybe.  The chinook pattern has been pushed back by at least 10 days by my count so far.  I think it likely we see some chinooks, and some inevitable warm days.  I mean, we are due some warm days.  TRI has been BN since Nov 26 - every, single day.  That is a stretch of nearly three weeks without a single day AN.  We live in the sub tropics - it is going to try to get warm in a multitude of ways.  TRI has recorded a trace or more of snowfall seven days this month.   IMBY, that probably adds up to maybe a couple of inches.  The number of days(not the total) with a trace or more is way AN.  Right now, TRI is -6.8 to start the month.

As for 84-85, JB mentioned it last week.  I didn't bring it to the forum with much discussion, because that is a landmark winter.  I did mention it to one poster on a sidebar to record the thought, and see what they thought.  I pulled the 500 pattern to look at it - made the map myself.  The 500 pattern looks exactly the same as the next four weeks on LR ext modeling at 500.  It is another reason I have been saying to be careful not to cancel winters.  And hey, we may go the way of dreaded '89, or we may score like 95-96 or we may chart an entirely new course (more likely). With so much cold available, all it would take is a decent NAO or EPO(even temporary)...and it discharges.  I don't think we go 84-85...but 95-96(light) would be the ceiling in my book.

But I think the hand wringing over an inevitable warm-up after three weeks of cold is not something this forum has traditionally taken part in, and hasn't this time.  We pride ourselves in not devolving into group think.  I also think it very important to look at model biases, and learn to factor those into thinking.  The Pac NW feedback is real, and it likely caused erroneous solutions at least for the dates Dec 15-22.  The repetitive Baja lows never materialized earlier this month - feedback error.  Let's see if that continues.  Infinite loops are real problems in computer programming, and wx models are not immune.  There is one other winter where this feedback occurred.  I will try to dig that winter up today.  Our conversations were almost identical as now.

I have noted many times.  In the IDF(Israeli Defense Forces), if everyone agrees...one person is required to take the other side.  It prevents mistakes.  I am thankful this forum doesn't try to drown out opposing viewpoints.   I think we do a pretty good job of that.  That is what makes our forum strong.

 

 

[Carvers Gap]

I also agree the WPO has been a key driver so far this winter.  JB has mentioned it a lot.  It has been extremely fickle to predict out past two weeks.  

[Carvers Gap]

One thing to watch is how wx modeling responds to potential negatives from the NAO/AO couplet.  I highly doubt those details are worked out.  Now, an NAO during mid-December is pretty meh in my book, but later in December...it could help.  Evidently, I cropped the model information from some of these.  The first is the GFS 6z AO plot.  The second is the NAO for the 6z GFS.  The third is the 0z EPS for the WPO.  The fourth is the EPS 0z NAO.  The fifth is the AO for the 0z EPS.  Those are not bad teleconnections for us.  Let's see how modeling builds those into their looks for the medium and LR.