December 2025 Short/Medium Range Forecast Thread

[John1122]

Saw a met today throwing out 1983 as a potential December analog. That was maybe the most frustrating winter month ever in my area at least. It was bitter cold, one day of warmth as a cutter passed, then ice box again. It was below zero on Christmas day. 

It warmed from the low 20s to the 50s early month, and rained 2 inches. Was in the low 40s and low 20s for a day, then it warmed into the 60s and rained an inch. It got very cold on the 19th, snowed a little over an inch with highs in the lower 20s on the 20th. Warmed up to 53 on the 22nd and rained nearly an inch, the bottom fell out and we got a dusting of snow on the 23rd and 24th, it was low single digits for highs on Christmas, with teens below zero lows. Dry as a chip. The high was 7 on the 26th, 24/2 on the 27th, it shot up to 48 on the 28th and rained again, just over an inch. That was ahead of another super potent cold front. Temps crashed behind it, it was 44 at midnight the 29th, and it fell to 2 by 11:00pm. It was negative 7 the morning of the 30th, and highs on New Years eve were in the teens. Through all that week of cold, we got around an inch and a half of snow but with that inch of rain in the few hours we were above freezing. 

 

All in all, December was around 8 to 9 degrees below normal,  we had almost 7 inches of precipitation, but barely managed 2 inches or so of snow to show for it, with less than that in some areas. It's the ultimate month that shows that no matter how perfect things should be with well BN temps and well AN precip, we're prone to getting shafted on snowfall. 

[jaxjagman]

6 hours ago, John1122 said:

Saw a met today throwing out 1983 as a potential December analog. That was maybe the most frustrating winter month ever in my area at least. It was bitter cold, one day of warmth as a cutter passed, then ice box again. It was below zero on Christmas day. 

It warmed from the low 20s to the 50s early month, and rained 2 inches. Was in the low 40s and low 20s for a day, then it warmed into the 60s and rained an inch. It got very cold on the 19th, snowed a little over an inch with highs in the lower 20s on the 20th. Warmed up to 53 on the 22nd and rained nearly an inch, the bottom fell out and we got a dusting of snow on the 23rd and 24th, it was low single digits for highs on Christmas, with teens below zero lows. Dry as a chip. The high was 7 on the 26th, 24/2 on the 27th, it shot up to 48 on the 28th and rained again, just over an inch. That was ahead of another super potent cold front. Temps crashed behind it, it was 44 at midnight the 29th, and it fell to 2 by 11:00pm. It was negative 7 the morning of the 30th, and highs on New Years eve were in the teens. Through all that week of cold, we got around an inch and a half of snow but with that inch of rain in the few hours we were above freezing. 

 

All in all, December was around 8 to 9 degrees below normal,  we had almost 7 inches of precipitation, but barely managed 2 inches or so of snow to show for it, with less than that in some areas. It's the ultimate month that shows that no matter how perfect things should be with well BN temps and well AN precip, we're prone to getting shafted on snowfall. 

BOM has the reconstructed MJO back to 1975 here,i know you look at analogs all the time maybe that can help out some

 

https://www.bom.gov.au/climate/mjo/#tabs=Monitoring

[jaxjagman]

Euro backed off from any SSW upcoming with not much of any wind reversal to what its been showing.JMA has the temps around -65C which is around what the Euro shows last update,Euro only shows the temps will get close to -60C in 10 days,so right now no SSW just some weakening,least not right now

[Daniel Boone]

11 hours ago, John1122 said:

Saw a met today throwing out 1983 as a potential December analog. That was maybe the most frustrating winter month ever in my area at least. It was bitter cold, one day of warmth as a cutter passed, then ice box again. It was below zero on Christmas day. 

It warmed from the low 20s to the 50s early month, and rained 2 inches. Was in the low 40s and low 20s for a day, then it warmed into the 60s and rained an inch. It got very cold on the 19th, snowed a little over an inch with highs in the lower 20s on the 20th. Warmed up to 53 on the 22nd and rained nearly an inch, the bottom fell out and we got a dusting of snow on the 23rd and 24th, it was low single digits for highs on Christmas, with teens below zero lows. Dry as a chip. The high was 7 on the 26th, 24/2 on the 27th, it shot up to 48 on the 28th and rained again, just over an inch. That was ahead of another super potent cold front. Temps crashed behind it, it was 44 at midnight the 29th, and it fell to 2 by 11:00pm. It was negative 7 the morning of the 30th, and highs on New Years eve were in the teens. Through all that week of cold, we got around an inch and a half of snow but with that inch of rain in the few hours we were above freezing. 

 

All in all, December was around 8 to 9 degrees below normal,  we had almost 7 inches of precipitation, but barely managed 2 inches or so of snow to show for it, with less than that in some areas. It's the ultimate month that shows that no matter how perfect things should be with well BN temps and well AN precip, we're prone to getting shafted on snowfall. 

Yep. It was a frustrating Month. Overall cold but precip almost all fell in the warmups. High of Zero on Christmas for coldest on Record. Not a flake of Snow !

[Met1985]

5 hours ago, jaxjagman said:

Euro backed off from any SSW upcoming with not much of any wind reversal to what its been showing.JMA has the temps around -65C which is around what the Euro shows last update,Euro only shows the temps will get close to -60C in 10 days,so right now no SSW just some weakening,least not right now

Im getting conflicting data. I just saw a post that said the 00z EPS looks like a go for wind reversal.  Although the PV being in a weakened state works as well.

[Met1985]

From Allan Huffman.

Well for all you #SSWE people out there. Today's 00z EPS showed all members (100%) showing a 10mb U wind reversal over the north pole around 11/28 to 11/29. The implications, are enhanced blocking risk in December and the possibility that the SPV will be further receptive to weakening later in the Winter which could influence the mid/late Winter.

Sent from my SM-G998U using Tapatalk

[jaxjagman]

38 minutes ago, Met1985 said:

From Allan Huffman.

Well for all you #SSWE people out there. Today's 00z EPS showed all members (100%) showing a 10mb U wind reversal over the north pole around 11/28 to 11/29. The implications, are enhanced blocking risk in December and the possibility that the SPV will be further receptive to weakening later in the Winter which could influence the mid/late Winter.

Sent from my SM-G998U using Tapatalk
 

 

39 minutes ago, Met1985 said:

From Allan Huffman.

Well for all you #SSWE people out there. Today's 00z EPS showed all members (100%) showing a 10mb U wind reversal over the north pole around 11/28 to 11/29. The implications, are enhanced blocking risk in December and the possibility that the SPV will be further receptive to weakening later in the Winter which could influence the mid/late Winter.

Sent from my SM-G998U using Tapatalk
 

I seen that this morning,

[jaxjagman]

The map he showed was the OZ,i assume early this morning,mine was yesterday afternoon,so it must have changed between

[Daniel Boone]

15 minutes ago, jaxjagman said:

The map he showed was the OZ,i assume early this morning,mine was yesterday afternoon,so it must have changed between

Yeah, yesterday backed off and today gained momentum. Models for you.

[jaxjagman]

EPS seems to be having a rough time to have such volatile swings

[Met1985]

23 minutes ago, jaxjagman said:

The map he showed was the OZ,i assume early this morning,mine was yesterday afternoon,so it must have changed between

Yeah yesterday didn't look as good but I mean it freaking changes daily.  But even a weakened state helps tremendously. 

[jaxjagman]

2 minutes ago, Met1985 said:

Yeah yesterday didn't look as good but I mean it freaking changes daily.  But even a weakened state helps tremendously. 

See what it shows this afternoon,shouild update in about  a hr and a half

[Daniel Boone]

10 minutes ago, jaxjagman said:

EPS seems to be having a rough time to have such volatile swings

Models usually get wonky when dealing with Stratosphereic Warming.

[Carvers Gap]

Yeah, sure bet SSW is wrecking havoc on what looked like a good pattern without it.  We have seen this many times during the past winters -> good pattern at range gets wrecked by an SSW.  The only positive with an SSW is that it could put very cold air over the eastern US.  My guess is that it dumps into western Canada and Montana and SLOWLY oozes west over a period of 1-2 weeks and modifies greatly.

The big thorn in the medium to LR is a cutoff low over the SW which dives into Baja to start December.  Until modeling works that out, the EC wx pattern is probably wrong.  If that is real, that will pump a monster SER over the SE.  There is ample precedence for this.  Sometimes modeling is correct.  Sometimes it is feedback.  The 12z Euro goes absolutely bonkers with it.  It creates a chinook over the southwest which pumps record heat into the souther half of the United States - like summer time heat for early December.

I have looked at major ensembles today at 12z, and they are just wrecked.  No other way to put it.  What do I mean by that?  Consistency is just shredded.  In "general," the can has been kicked by a week at least.  The Weeklies caught this first.  I may just start using the Weeklies...LOL.  However, the MJO and ensembles definitely foretell of a huge trough over eastern Canada by d14-16.  Problem?  The SER is flexed big time, and that standing wave is gonna have to get knocked down w/ several cold fronts.  It cuts the bottom out of the trough.   Seasonable cold looks like the outcome if today's iteration is correct, and it probably isn't.  Let's hope the EURO AIFS and GEPS are correct, and they could be.

For now, I am kind of watching the timeframe just after Thanksgiving.  I wouldn't be surprised to see a NW flow event or storm pop w/ that.  500 vort maps are not missing by much when it comes to both streams.

Overall, I think the cold is coming, but any time models start "can kicking" in unison, be very careful about expectations.  I wouldn't be surprised to see a record cold outbreak.  I wouldn't be surprised to see it completely vanish at our latitude.  

My gut says extreme cold is coming for the Mountain West.  Why do I think this?  15 years of watching it do that 90% of the time.  It will make its way here probably between Dec 10-25.  Then we warm up.  I suspect the cold reloads quickly and we see another bout to start the new year.  While I am bearish now for early December, I still think we see a reloading cold pattern which is prob the result of the SSW.  But for now, I am "out" on early December extremed cold.  I think it will be seasonable to AN for week one, transition week 2, and maybe a cold week 3 before warming back up...and reload.  

[Carvers Gap]

I had a ton of posts up this morning, but as I dug through modeling one thing was clear...ensembles and their deterministic runs were signaling a big warm-up after the Thanksgiving cold.  How long does it last?  IDK.  In a rare move, I deleted all of those posts.  Why? When modeling moves in unison towards warm...something is afoot and it usually isn't cold.  The MJO argues for a very sharp cold trend in LR modeling which is not present yet.  Sometimes, modeling doesn't "see" the MJO until about d10-12.  The problem is the MJO really doesn't drive winter weather until Jan/Feb...and maybe late December.  Right now, everything is very volatile after d10.  Extreme cold is still on the table but kicked to December 8th or later IMHO.  Outside of experienced mets, nobody knows what is coming w/ that cutoff low and SSW projected.  An amplified pattern appears likely with wild swings between cold and warm.

[Carvers Gap]

There should be some wild model swings, but we are gonna have to let the dust settle after the past 24 hours of models flip flopping.  They may go back cold like the AIFS.  They may trend much warmer if that cutoff is really.  So things to watch?  Does that cutoff leave the SW or does it stall out?  If it cuts of and stalls -> SER here.  If it ejects -> big time cutter w/ cold following.  Until that gets worked out, just guess work.

[jaxjagman]

Thinking the same thing @ Carver.Like Jeff metioned a week or two ago,its gonna take a couple CF's to beat down the SER,before it can get really cold,otherwise its just gonna be transient cool down i agree also the Euro suites struggle with systems out west,more than likely today with that trough out west.GEFS dont show much change today,not perfect but not as extreme as the EPS

[Carvers Gap]

I mean really this is just a repeat of the start of our past La Nina winters for the past decade, including the model delay of cold air.  What I am really interested in is this....With this shakeup on modeling, does it displace the entire pattern cycle by at least 7-10 days IMHO???  That may well leave us cold to start January - maybe.  

[jaxjagman]

LOL

1 hour ago, Met1985 said:

From Allan Huffman.

Well for all you #SSWE people out there. Today's 00z EPS showed all members (100%) showing a 10mb U wind reversal over the north pole around 11/28 to 11/29. The implications, are enhanced blocking risk in December and the possibility that the SPV will be further receptive to weakening later in the Winter which could influence the mid/late Winter.

Sent from my SM-G998U using Tapatalk
 

Looks like the quite a few members jumped the train today...lol

[Daniel Boone]

34 minutes ago, Carvers Gap said:

There should be some wild model swings, but we are gonna have to let the dust settle after the past 24 hours of models flip flopping.  They may go back cold like the AIFS.  They may trend much warmer if that cutoff is really.  So things to watch?  Does that cutoff leave the SW or does it stall out?  If it cuts of and stalls -> SER here.  If it ejects -> big time cutter w/ cold following.  Until that gets worked out, just guess work.

That was my worry when I alluded to SW Trough yesterday. 

[Daniel Boone]

The one bias we hope turns out to be the case here is the Euro holding energy back in the SW.

[nrgjeff]

Deterministic models are pure chaos. Ensembles are flopping around but one can at least find some reasoning for that. After the Thanking cold a brief warmer episode is likely because of a little -PNA. However the Alaska ridge persists, so warmth probably won't. In fact by day 15 the EPS and somewhat GEFS hint at cross polar flow.

Some support for return to cold mid-December, and perhaps lasting, comes from a retrograding Rossby wave. Since that's a 500mb feature we don't need to debate the SSW. Strato heights are well AN and want to reflect at 500mb. While I don't believe SSW wrecks cold patterns, it doesn't always favor North America. SSW signal is best for Eurasia. Things like the Rossby wave can turn odds for North America.

The weekly charts may be picking up on all this. They go with the warmer week before settling into a colder regime with less back and forth. We'll see. Stuff changes every day. Who knows if all the background forecasts verify? At least the results make some sense this afternoon. 

[Carvers Gap]

39 minutes ago, Daniel Boone said:

That was my worry when I alluded to SW Trough yesterday. 

IMHI, it really isn’t a Texas Blue Norther.  That Euro cutoff partially pumps a ridge which locks all but the northern tier out of the cold during the first week of Dec.  It is the Four Corners cutoff which drifts southwest into Baja and slowly runs out of steam…that is the pattern issue in my book.  I am fine with a SW cutoff which eventually kicks out - pay me now or pay me later set up.  The slow stall and drift into Baja is the thorn.

The good thing is most ensembles get to the same EPO/PNA ridge setup by ~d14.  The NAO(chuck mentions this in the MA) has gone poof, and that doesn’t push BN heights(over Canada) as far south as originally prognosticated.  The Weeklies are only half completed as I type.
 

I see Jeff has posted.  Gonna hit enter and read it.

 

[Carvers Gap]

The Euro Weeklies look like they have for the past 3-4 weeks which is cold weeks 3-6 w a warm up at the very end.  They were prob a bit quick with the pattern change.  They are about two weeks delayed from the original cold looks of a few weeks ago.  For now, I think Dec 10 to just a few days after NYs looks BN for temps.  For snow lovers, the concern would be cold and dry.   The good thing about a +NAO is that the Gulf would likely be open for business.  Could be warm up and rain…just have to time it with some of those inevitable highs coming from the prairies of MT.

With a potential for SSW…we could see the cold hit 2-3 weeks after which would be an extension of cold into Jan.   Model chaos on the horizon indeed.