December 2025 Short/Medium Range Forecast Thread

[Carvers Gap]

OTH, if January and Feb go to pot....my winter forecast from June scores yet again.  LOL.  FTR, I hope it doesn't verify.  

I think Larry Cosgrove nailed this seasonal outlook with the exception of the first 2.5 weeks of December being cold.  I strongly encourage everyone to find him on FB and read that seasonal outlook.  He has been zigging while everyone else has been zagging.  If he is right, and I have no reason to think he isn't, we will all be happy by the end of Feb.  But as Larry noted, patience will be king this winter.

Just imagine this pattern, but with January cold forcing its way southeast.  What happens in November(and early December), the winter often remembers.

[Carvers Gap]

BTW, Larry's idea is that winter's worst is from late January into March...and rough at that.  Gotta run.   Sorry, I hadn't posted much this morning.  

Dear Facebook, as I was pulling out of the garage I ran over a can full of blue paint.  It exploded under my truck.  I didn't know it until I drove around my cul de sac - twice!  I got to scrub lots of asphalt and the garage floor.  Meanwhile, I had to do a NASCAR fast wash down of the truck in order to get it on the road for one of my kids.  Anyway, BN heights(aqua blue...don't even get me started on how that color wound up in paint storage) went all over the place!!!  Maybe it is some kind of sign.

Trust me, I would rather be looking at raging warm weather models.  Haha.  Don't have sympathy.  Just know if you are having that kind of day...you are not alone!!!

[Carvers Gap]

Now that I am back and things have settled down a bit, here are a thought or two...

1.  Recent Nina winters have followed a fairly predictable pattern.  Cold end to November, cold start December, flip to warm around Christmas. and cold returns for late Jan and Feb, especially middle and western areas of the forum.

2.  I don't trust models right now past ten days - if that.  There has been a lot of feedback in the usual places.  So, pivot back to point number one....

3.  To me, the real question is whether we get one final cold shot right before Christmas - 50/50 for me on that one.  I think the warm-up after Christmas has been well advertised.  We know how the last warm-up worked out - cold.  Let's see how this one goes.

4.  There are things to track prior to Christmas.  I see roughly (4) windows to monitor.   I will try to dig a bit deeper later.  I got 0z, 6z, and 12z to look back through.  Tomorrow is gonna be even crazier.  

[Daniel Boone]

2 hours ago, John1122 said:

The Pacific hates us. It seems to always find a way to screw up everything for us. 

Yep. That Aleutian HP is where we need the LP to be. Need that HP over Alaska and need that LP near the GOA to move to Aleutians. As is, that Pac Jet's going to roar between the Goa Low and the Epac and West Coast Ridge. if it comes in strong enough it'll flood the US with Pacific Air and downslope off the Rockies spreading warmth. If it were to blast in further North it could potentially flood western and central Canada scouring the cold out. Kentucky Post was right on with that post about needing that Ridge to link with the Alaskan HP. 

[John1122]

32 minutes ago, Daniel Boone said:

Yep. That Aleutian HP is where we need the LP to be. Need that HP over Alaska and need that LP near the GOA to move to Aleutians. As is, that Pac Jet's going to roar between the Goa Low and the Epac and West Coast Ridge. if it comes in strong enough it'll flood the US with Pacific Air and downslope off the Rockies spreading warmth. If it were to blast in further North it could potentially flood western and central Canada scouring the cold out. Kentucky Post was right on with that post about needing that Ridge to link with the Alaskan HP. 

We needed the Pac jet to help pop the PNA but it's not worked out that way. 

[jaxjagman]

We'll know more in the next couple days where the MJO is going,now is when its getting destructive interference from Rossby/Kelvin Waves

[jaxjagman]

GTH Outlook Discussion

Last Updated - 12/09/25

Valid - 12/17/25 - 12/30/25

Following a very high amplitude Madden Julian Oscillation (MJO) propagation across the Pacific at the end of November, the intraseasonal signal has rapidly weakened as it crossed the Americas and Atlantic in early December and now resides within the unit circle. The strong MJO event was the result of constructive interference between the MJO itself and Kelvin Wave (KW) activity which have become more decoupled in recent days. Long range dynamical model ensembles depict the RMM-based MJO signal generally remaining within the unit circle, with some re-emergence into the Western Hemisphere around the end of week-2. While the GEFS and ECMWF show this evolution to some degree, the CFS is the most robust in its depiction of a more coherent loop of the RMM-based signal which comes out of the unit circle in phases 7 and 8 later in December. Velocity potential filtering indicates a very fast moving enhanced convective signal circumnavigating the globe during the next 2 weeks, despite the lack of an RMM-based signal appearing over the Eastern Hemisphere. However, an experimental projection of objectively filtered KW activity in phase space reveals a continuously circumnavigating signal, which at times constructively and destructively interferes with lower frequency modes. This makes for a rather complex and low confidence Global Tropics Hazards Outlook and is based mainly on La Nina composites and some consideration of dynamical models.

[Carvers Gap]

Anafront watch.....The 18z GEFS has 14 members with it.  Some fronts have already passed through on this slide.  Some are in process.  Some are yet to come....

 

[jaxjagman]

Kinda looks like Christmas eve,1988

 

 

 

[Daniel Boone]

1 hour ago, jaxjagman said:

Kinda looks like Christmas eve,1988

 

 

 

Yeah, terrible. Definitely not festive in the Weather Department unless you're into that kind of Christmas. That would be samey as a Winter wx lover enjoying Snow on the 4th of July, lol.

   That Winter had below average Snowfall.

[Holston_River_Rambler]

EasternLI had a pretty good post in the main forum ENSO thread last evening. It’s somewhat pro-wintry wrt the MJO handwringing of snow weeniedom across several wx forums right now. Read it or not, up to y'all, but it attempts to sort through some of the mixed signals on models later this month. I would try to summarize it, but have to get on the road early this AM. 

[Carvers Gap]

Sometimes when we look at weather in the d10-15, we miss the stuff right in front of us.  Light snow is possible tonight across NE TN and SW VA(assuming that also means SE KY).  Then, again on Friday w/ a slightly more "vigorous" system.  WWAs have been hoisted for portions of those areas for tonight - mainly higher elevations.

[Carvers Gap]

National Weather Service Morristown TN
611 AM EST Wed Dec 10 2025

...New AVIATION...

.KEY MESSAGES...
Updated at 609 AM EST Wed Dec 10 2025

- Dry and warmer to start today, before a cold front arrival later
  tonight. Gusty winds ahead of the front for the forecast area.
  Wind Advisory in effect for all except the southern part of the
  forecast area.

- NW flow snow event expected later today through early Thursday
  with accumulating snow over parts of the Southern Appalachians
  and higher terrain of southwest Virgina. A Winter Weather
  Advisory has been issued.

- We will warm up again late week with low chances of
  precipitation across the north.

- Stronger cold front Sunday into Monday will considerably drop
  temperatures. Lows in the teens with some single digits Monday
  morning. Cold wind chills also possible.

&&

.DISCUSSION...
Issued at 1138 PM EST Tue Dec 9 2025

The forecast for today has come into better agreement over Wind
Advisory level winds for everywhere north of the southern valley
and southern plateau later today. As well as an accumulating snow
event for northwest flow prone locations of the forecast area;
Southern Appalachians and parts of southwest Virginia.
Temperatures will be warmer today, however, cloud cover will be on
the rise.

Almost advisory level winds are being observed at Cove Mountain
with gusts in the upper 30s at the time of this discussion. A WSW
LLJ will increase into the overnight hours, bringing increasing
winds to the higher terrain. Later in the day as mixing occurs,
the gusty conditions will translate to the surface for the lower
elevations, hence the advisory covering the day-time. A heavier
weighted blend of the HREF/RRFS was used to capture the usually
overperforming SWly winds for the valley. Gusty winds will
continue into Thursday morning for the higher terrain, slowly
decreasing behind the FROPA. A Wind Advisory is in effect later
this morning first beginning in the mountains, expanding to the
lower elevations, later finishing for the mountains early
tomorrow.

Confidence has also increased on higher snowfall amounts for the
higher terrain with the latest guidance. The day will start warm,
but temperatures will fall coinciding with the cold front later
this evening. Rain will transition to a rain/snow mix, and then
eventually all snow for elevations primarily above 2500 feet.
Low-level moisture, NW winds, and temperatures below freezing are
evident on forecast soundings, all supporting northwest flow snow.
Snow will end early to mid Thursday when low-level winds drop off
and lose the NWly component. Total snowfall accumulations will
generally be 1 to 3 inches with higher mountain tops possibly
seeing above that, for example, LeConte may see up to 5 inches.
It`s possible some light snowfall may be seen across lower
elevations of the northern valley and plateau, but is generally
not favorable with NWly flow due to more downsloping on the valley
side, which means drier. A Winter Weather Advisory has been issued
and will begin mid-day, running 24 hours highlighting the
potential for the aforementioned areas.

Following the snow`s exit Thursday, a short cool-down can be
expected with drier conditions throughout the day and decreasing
cloud cover. However, precipitation from a weak system will bring
increased chances to northern parts of the CWA Friday. Meanwhile,
upper heights will be rising which will bring the warmer
temperatures back for Friday and Saturday.

Later this weekend becomes a bit complicated in regards to
more precipitation due to potential interaction of southern and
northern stream systems, but the one thing models agree on, is a
substantial drop in temperatures Sunday into early Monday. Strong
high pressure is expected to barrel its way through, originating
from Alaska and Western Canada, where temperatures there have been
in the 50s below at night, but we will not see that here. Monday
morning lows are currently forecast to be in the teens with some
single digits for the highest elevations and parts of southwest
Virginia. Wind appears will be on the decline once we get later in
the night Sunday into Monday, which is good news and may suppress
what could be much worse wind chills. High pressure will
eventually shift eastward but will keep us dry through at least
early Tuesday.

 

[Carvers Gap]

This is the GFES ext from last night....this is its 35d map.

[Carvers Gap]

From what I can tell on the 6z GFS, the warmth rolls in and the warmth rolls out w/ each cold front.  The warmth in the medium/LR is originating from a chinook.  Whether that is MJO related, feel free to debate.  However, as we have seen with other warmups, the warmth on deterministic models is being eroded into shorter timeframes as it gets closer.  At one point, medium range modeling had the Dec 14th system moderated to a minor cold front passage.  As is, we likely see very cold wind chills with this and temps in the lower teens and upper single digits in portions of NE TN.  The mountains will be below zero.

Just using the 6z GFS which looks reasonable.  Temps warm on Dec18th and 19th before another cool front arrives.  Then temps warm from Dec 21-24, before the GFS slams the door on it.  The danger w/ this Dec 20th front is that modeling could be too weak.  The 0z CMC has what looks to be an anafront line up in the Plains during that time.  A trend I have noticed w/ modeling is that cold fronts are modeled as pretty vigorous at range.  Then, they are moderated...then w/ about 7-10 days to go...the are much colder yet again.

Just combing through ensembles this AM...the 0z GEFS erases the aforementioned chinook warmth by Dec 26.  The 6z GEFS is still rolling.  

The 0z CFSv2 basically repeated the current pattern through the entire run.  It has a strong cold shot to end December and begin January.   More on that later if 6z and 12z support that run.

The trend we have been seeing for weeks is modeling which moderates temps of warmth which roll through.

TRI is -5.4F for the month so far.

[Carvers Gap]

Just looking at yesterday’s Euro weeklies which have been the source of much gnashing of teeth and have the worst possible of all the outcomes.  Warms up Christmas and is back to this current colder pattern by mid Jan.  Wash, rinse, repeat.  Actually, temps return to seasonal abruptly during the second week of Jan.  Seasonal during that time frame will get the job done.

[Carvers Gap]

For kicks and giggles, take a look at the blizzard warning posted for West VA.