December 2025 Short/Medium Range Forecast Thread

[Daniel Boone]

9 minutes ago, Carvers Gap said:

It is back to 6" for portions of Sullivan Co on the 12z today.  The AIFS has 1-3".  I still think it is over done, but the GFS can sometimes score a weird coup from time to time.  For now it is an extreme outlier.  I wouldn't be surprised for NW facing slopes to see 1-2" out of that system tomorrow night.

The GFS may score here as the same thing as far as mosisture is concerned may do as last System. It kinda looks like an anafrontal wave deal or Lee Low Snow Print.

[Carvers Gap]

12 minutes ago, Daniel Boone said:

I guess I still go by 1980 to 2010 Averages more. The Avgerages have really jumped over the year's and the thing is that's not always caught is the last sevral Year's that jump is added on in the NWS Station Avgs. The Avg high for Pennington gap this Date was 47 Hi 27 low in 2010 I think. So, average is running below that for the balance but not extreme( however, I think that has gone up some now). KTRI  now says the Average high there is like 51 or so Low 31 I think. That's several degrees milder than used to be for there.  

So, with "Today's" Averages we're running a good bit below. the point basically being the difference in comparison to our west and East. There is a Spike through here of not of below as the aforementioned. I think John actually hit it with the western Ridge Height as far as the point being addressed. 

    I see your reasoning though as the cold we have got has been constant. Of which is a rarity, especially this early.

      

Models haven't missed by much with the exception of the 4-5 day SER/feedback hiccup.  They really haven't amplified the pattern with just a few exceptions.  Mid-month may well change that.  I think the wavelengths are just flatter, and that may help us later on as this will be tough to dislodge as climo gets increasingly colder.  This has been a pretty cold start IMBY.  I do think there is a window for a piece of the TPV to drop into NA to lower latitudes than the GL.  Also, you noted that the Pac NW has been pretty active.  That Pac flow also might be modifying the colder temps at the base of the trough, and that was shown on modeling.  Interestingly, the Sierra Nevadas in California and the Colorado Rockies have been stuck under that ridge, and are way, way BN on snowfall.   Lastly, the pattern doesn't really amplify in phase 7 of the MJO, but it can w/ phase 8.  I think modeling erroneously tried to loop the MJO, and that made a mess.  Now, it is forecast to stall by some models in phase 8.  It may just keep on making the circuit, but...it did make a turn(per the EMON) today which could signal a stall.  We will know more in a few days.  Overall though, this has been a very cold start IMBY.

[Carvers Gap]

5 minutes ago, Daniel Boone said:

The GFS may score here as the same thing as far as mosisture is concerned may do as last System. It kinda looks like an anafrontal wave deal or Lee Low Snow Print.

If we see that really cold shot between Dec 14-16, I would say we have a 50/50 shot(or better) at a strong anafront.  As for Sunday night, I have no idea...it is interesting to see the GFS hang onto that.  Overall, we need that ridge to backup just a bit.  I see where several folks on other forums have been talking about -PNA.  I don't know if that is a true -PNA.  That looks like a +PNA on modeling, and it is centered a bit too far to the east.

[Carvers Gap]

Congratulations, everyone.  The HOT donuts sign is on for this thread.  Haha!  Now, I am gonna go watch some football. 

[Carvers Gap]

There is a noticeable and significant uptick in juice w/ the 18z short range models w/ regards to Sunday night.  The GFS continues w/ its outlier look in NE TN, but the 18z(edit) NAM has the same deformation band.   Almost all short range models now have increased backing over Virginia and/or North Carolina.  Can it get west of the Apps???  I don't know about that.

[Carvers Gap]

 

[Carvers Gap]

That forms a light anafront and then a Nor'easter.  IMHO, that would form a blizzard for the NE.  

[Carvers Gap]

The 18z GFS has a second cold front roaring down the Plains at d12. This one could be colder.

[Carvers Gap]

Bonified anafront (second of the run) w/ the second cold front.  The Southern Apps will have a foot and a half of snow by the end of this run.  

[Carvers Gap]

Just one Arctic air mass after another.

[BNAwx]

2 hours ago, Carvers Gap said:

Just one Arctic air mass after another.

I’ll be a little surprised if a sneaky clipper or two doesn’t pop up in the upcoming pattern.

[Daniel Boone]

HRRR showing similar outcome with this System coming up Tomorrow night as the past one. Rich get Richer if is right as showing this Evening. Hopefully it's wrong. If not, more cold rain with a little sleet and snow mixed in for area's south of Wise and Lebanon ending as Snow. Wouldn't surprise me at all. 

[Holston_River_Rambler]

Pretty decent NAMing for parts of SW VA at 12z. Especially areas NE of Abington towards Wytheville. 

[Daniel Boone]

1 hour ago, Holston_River_Rambler said:

Pretty decent NAMing for parts of SW VA at 12z. Especially areas NE of Abington towards Wytheville. 

Yep. Snow on snow up that way.

[Daniel Boone]

51 degree's here ! I almost pulled the trigger yesterday saying I wouldn't be surprised if we hit 50. The Great Valley warm nose, lol. 

[fountainguy97]

55 here now! Hrrr and nam both keep the border counties snow. Looks like a nice 1-2" surprise may be in store for my area. I'll believe it when it's falling from the sky though.

[Daniel Boone]

1 minute ago, fountainguy97 said:

55 here now! Hrrr and nam both keep the border counties snow. Looks like a nice 1-2" surprise may be in store for my area. I'll believe it when it's falling from the sky though.

I don't blame you. At this point, how can you believe it after what happened Friday and also today's milder outcome. To add insult to injury, several inches expected at Virginia Beach and down the NE Nc Beach area.

[Carvers Gap]

A warming trend is present after hour 300.  Is it destined for the reality of the previously modeled LR warmups?  I think so.  I don't doubt that we could see a warmup, but the MJO is parked on the left side or a bit.  Any warmup should be short lived IMHO.

As for the minor system affecting NE TN and SW VA tonight and tomorrow?  Time of day probably keeps this from being much of a problem in TRI, but.....I am not unconvinced that eastern portions of TRI aren't going to see 1-3" of snow.  Bristol, Elizabethton, Roan Mountain City, Unicoi, Erwin, and eastern JC.  These are TRICKY little systems to figure out, and modeling supports snow in those areas - 18z 3K NAM, 18z HRRR, 12z RGEM, 12z GFS, 12z CMC.  I think west of I-81 the dynamics get here after the best forcing exits.  But we need to watch trends this evening.  I have seen system like this score in amazing ways.

 

[John1122]

We are going to need some kind of shake up to the pattern to see widespread snow. I don't remember seeing many ridges out west that were sprawled out so far west to east vs south to north. That's pretty much killing our chances of having a storm track that works for us. Nothing is going on in the southern stream really, and clippers are shunted too far NE for us due to that ridge alignment. Unfortunately the PNA is forecast to remain - for the next 14 days with the west/east ridge. We are going for 10 days of mostly dry weather across 95 percent of the forum area with less than .10 qpf falling. 

As soon as that pattern breaks a little it will warm up and rain, no doubt.

[Carvers Gap]

Both the 18z RGEM and GEFS hold serve over extreme NE TN.  I have strong doubts about snow in TRI, but the GFS is no longer alone w/ the this system as noted above.  From I81 to the east, there is snow modeled on almost all models w/ the exception of the Euro.  The closer to the foothills one goes, the stronger the totals.  This is definitely a trackable system for NE TN and SW VA folks(Abingdon vicinity).  It is no slam dunk, but interesting nonetheless to see the GFS pick up support.  Now, before folks accuse me of favoring MBY...this, in fact, does not appear to have much of an impact IMBY.  In fact, if correct, I will be able to drive 10 minutes to my east and find snow.  LOL.

[Carvers Gap]

As an explanation for those who don't live in NE TN, one of the real pains which we(in TRI) have to deal with(regarding modeling) is that models will sometimes smooth the cutoff for elevation snows into regions which don't have elevation.  Most people think NE TN is high elevation....we are not, but we are very close to places which are.  What is difficult to know about recent model runs...is whether smoothing is playing a role in the strong totals east of I-81.  But for anyone who has lived up here for very long, we have had some systems with wild and crazy snow cutoffs regarding accumulation.  We had a guy from work one time who said he would be out for the week due to snow.  We thought he was just pulling our legs.  He was only 20 minutes away.  Nope, that man had like 2-3 feet of snow in his yard.  We had a dusting.  I am NOT expecting that this time, but I could see foothills communities doing well...but modeling is not to be trusted when some have a bunch of snow and others have none.  Could bust either way.

[Carvers Gap]

As for the medium and LR pattern, ensembles and deterministic modeling still favor some amplification mid-month. Whatever we get is likely going to be northern stream influence. 

[Carvers Gap]

I think our next trackable system is around Dec 11th - very light NE TN, SE KY, SW VA, possible Plateau.  Then, I think our best chance will be around Dec 14th.  As long as that cold front presses into our area w/ full force, I think we likely see frozen precip then.   The 18z GFS shows the potential for that one.  It is running as we speak.