December 2025 Short/Medium Range Forecast Thread

[Carvers Gap]

The 18z RGEM is threatening to bring frozen precip into the forum area around Dec 5th.  Sneaky system...a little bit of ZR can wreck total havoc.

[Carvers Gap]

The 18z ICON is flirting with it as well for NE TN/SW VA.  Time of day is huge.  If that comes in over night, it could be a mess.

[Carvers Gap]

The 12z Euro is northern stream dominant after Dec 5 w/ like (3) systems coming through.  Rain/snow mix for the valley.  Nice look.

[Daniel Boone]

18 minutes ago, Carvers Gap said:

The 12z Euro is northern stream dominant after Dec 5 w/ like (3) systems coming through.  Rain/snow mix for the valley.  Nice look.

Yeah, if blocking is decent during that Time we should fair well. If the Pac Jet doesn't blast the PNW like some guidance is showing some of that really cold air should finally get to us. The MJO may help alter that Jets direction more than what the GFS in particular is showing and thereby a colder outcome. As it stands, Could be quite cold and snowy or cool and damp . We shall see.

[Carvers Gap]

1 hour ago, Daniel Boone said:

Yeah, if blocking is decent during that Time we should fair well. If the Pac Jet doesn't blast the PNW like some guidance is showing some of that really cold air should finally get to us. The MJO may help alter that Jets direction more than what the GFS in particular is showing and thereby a colder outcome. As it stands, Could be quite cold and snowy or cool and damp . We shall see.

The GFS is a an outlier at this point but has come around some today.  It was an extreme outlier yesterday.  I mean eventually it will be right when the MJO finally rotates around.   A broke clock…

[Maggie Valley Steve]

I'm sure you folks are aware of another SSW Event unfolding for mid month?

[Daniel Boone]

4 minutes ago, Maggie Valley Steve said:

I'm sure you folks are aware of another SSW Event unfolding for mid month?

Yeah, there's some talk of it being a complete SSWE. PV is weak so if there is one it may very split the PV this time.

[Carvers Gap]

12 minutes ago, Maggie Valley Steve said:

I'm sure you folks are aware of another SSW Event unfolding for mid month?

Thanks for the heads up.  I prob should look at the strat more.  Generally, I just wanted it jostled and not spinning in a tight spiral.  That would make sense given that this has occurred during recent Nina episodes.  That would set the stage or cold by mid January.  This could be a crazy winter.

[Holston_River_Rambler]

You know, if we ever wanted an Aleutian trough, we have one, at least for now. Absolutely massive trough, maybe just a bit too far west. 

[Carvers Gap]

Weather models amaze me.  What a front.  These are the real feel and anomaly maps from the 18z GFS at 360.  In no way shape or form am I saying this going to come to pass on this exact day.  However, I do think an extreme front is on the table as is record heat by mid month.  We could see both...I hope not on the same day.  But we could see some extremes.

 

[Carvers Gap]

And yes, that is an anafront - textbook.

[Carvers Gap]

You want wild?  The 18z AIFS has mid 60s all they way into Iowa at the same hour as above.  Models are ALL OVER THE PLACE this evening.  That is a pretty good sign that cold is coming into the Lower 48.   Temps differences are almost 70 degrees in some places between the 18z GFS and AIFS.  And at 360, that isn't completely unexpected, but it is wild to look at.  I think we have cold through mid month, and then paths diverge.  I do think we "could" see some strong cold fronts, maybe sever weather, and possible frozen events.  

[Daniel Boone]

1 hour ago, Carvers Gap said:

You want wild?  The 18z AIFS has mid 60s all they way into Iowa at the same hour as above.  Models are ALL OVER THE PLACE this evening.  That is a pretty good sign that cold is coming into the Lower 48.   Temps differences are almost 70 degrees in some places between the 18z GFS and AIFS.  And at 360, that isn't completely unexpected, but it is wild to look at.  I think we have cold through mid month, and then paths diverge.  I do think we "could" see some strong cold fronts, maybe sever weather, and possible frozen events.  

Could be the Strat thing playing havoc on Model's or the forecasted strong Pac Jet or both. The MJO should be in a cold phase then. Blocking should be in place so ., just don't know.

Extreme heat( for even there this late) is lurking in the deep SE and over the Gulf and portions of Mexico so, wouldn't take alot to soar Temps if flow shoots from that way. In fact , some of the milder air aloft now is a result of that being sifted north toward the Jet. That huge area of extreme warmth originally spread from Mexico and Texas a couple Weeks ago along with that now Cuban HP that was forecasted last week to be a huge SER with near record warmth here. 

    I'm in hopes that HP and area of heat gets shunted eastward toward the Sargasso Sea as it may cause us issues throughout the Winter if not. I've seen it before. The Aleutians Trough is a bit too west as well as Holston noted. Place that a bit east and shift the pattern that much East and we'd be situated about where Western KY is within the Trough now. Those are a couple things that would help us if they shift.

A bit of an apendage ; the Cuban HP can occasionally be of benefit, particularly with Overrunning Events so, it's not always bad. It just doesn't happen often. We'd still be much better overall if it were shunted out as mentioned above.

 

[John1122]

The models are just chaos still. Near misses, just too warm for snow events, one late anafrontal for the far east on the gfs. They keep attempting to put a huge trough in the west that so far, has never materialized. Looking at the models 10-12 days ago we should have been torching right now with a big western trough and instead it's 37 with rain here and western areas of the forum have a winter weather advisory. 

[Carvers Gap]

The 6z GFS is frigid late in its run.  Going to be interesting to look at MJO plots this morning. 

[Carvers Gap]

Let's see if the GFS holds on to this ana front idea.  It likely won't be there each time, but that is now 2 of the last 3 runs(18z and now 6z).  If I remember correctly, it has a knack for that - I cold be wrong. 

I do think there will be some sort of warm-up embedded in all of this.  It looks like mid-month is when it is most likely.  Right now, I just think modeling is not recognizing the MJO very well at all.  That is why I want to look at the plots this morning.

Until the MJO moves to the right side...I have my doubts about any sustained warmup.

Even the 0z Euro has an anafront of sorts at the end of its run w/ severe in front of it(not uncommon in my experience).

[Holston_River_Rambler]

8 minutes ago, Carvers Gap said:

Even the 0z Euro has an anafront of sorts at the end of its run w/ severe in front of it(not uncommon in my experience).

True. We need some thunder in the mountains! That index has bottomed out for now. 

[Holston_River_Rambler]

I created a Winter 25/26 general obs thread in case anyone sees some snow this AM 

@Knoxtron and @John1122 I'm staring at y'all with jealousy. 

[Carvers Gap]

Well now, that is a proper 12z suite incoming.

[Carvers Gap]

I don't have any thunder in the mountains, but I am bringing this to the table... The Madden Julian Oscillation has an odd resemblance to the Death Star.

[Holston_River_Rambler]

32 minutes ago, Carvers Gap said:

I don't have any thunder in the mountains, but I am bringing this to the table... The Madden Julian Oscillation has an odd resemblance to the Death Star.

I swear it did that before one time last year when it tried to get it phase 8. 

[Daniel Boone]

The European Models bring the Goods Friday and Saturday to NETN, SWVA and SEKY . General 2-6". 

[Carvers Gap]

Both the 12z RGEM and Euro(see Boone commit above) have a system next weekend.  By default the CMC has it as well.  Looks like a time of day type of deal.  Plenty of northern stream energy after that.  I suspect modeling is too quick with exiting the cold eastern pattern.  I do think a ridge rolls through though, and a stout one at that.  I also think an anafront is still on the table.

[Carvers Gap]

The 12z Euro essentially has an anafront at the end of its run.  The front isn't as north/south as we would want it, but it is good that is still showing.  I think we see incredible return flow in front of it - likely record highs and severe.  Then that baby pushes through and things freeze solid.  Let's see if that hypothesis holds.

[Daniel Boone]

1 hour ago, Carvers Gap said:

The 12z Euro essentially has an anafront at the end of its run.  The front isn't as north/south as we would want it, but it is good that is still showing.  I think we incredible return flow in front of it - likely record highs and sever.  Then that baby pushes through and things freeze solid.  Let's see if that hypothesis holds.

I agree with you completely . If we go back to many great Winter's, many of them featured that occurrence. '95-96 comes to mind as that happened on more than one Occasion. Not saying we're in for a "great" Winter , although, the possibility does exist. I think if that Mild shot is short and ends abruptly the Odds are pretty good imo.

[Carvers Gap]

Typos should be fixed in that last post...at least you know it isn't chatGPT or Grok generated stuff from me!  The typos tell the tale.

Anyway, remember how I always say to look out when the control doesn't match the ensemble with the Euro Weeklies?  The control has a habit(as does the GFS at range) at sniffing out bigger fronts.  I think reality is closer to the control.  I think ensembles are too washed out.  What we are seeing is a strong presence of cold in the Canadian Prairies and Northern Plains in the LR.  The pattern in our area is cold front -> warm up -> cold front...wash, rinse, repeat.  The ensemble washes that out, but the control does not.  

I think the Lower 48 may see a pretty strong cold outbreak.  Does it head to the West first?  Likely.  But.....if it comes down the Plains in the form of an anafront, it is gonna be freakin' cold howler.  I am going to take a look at afternoon individual ensembles to see how many have that type of strong cold front.

 

[Carvers Gap]

And take what I just posted and compare it to the 12z CFSv2...

[Carvers Gap]

Then compare those to the very end of the 12z Euro.  See that big ridge in Alaska?  We know the Euro has a tendency to feedback in the West.  If that trough corrects eastward(which it should) and it is actually real, that sets the stage for very cold air to rapidly flood into the NA mid-section.   As Boone noted above, it is very common for extreme warmth to get pulled ahead of strong cold shots.  You can see the warmth surging into New England.  During old school winters, many great cold shots were preceded by storms and rain.  

There is also a path to very warm temps.  But beware.  We have noted that modeling feeds back in the Southwest.  But...it also feeds back in the lee of the Rockies in Canada when extremely cold air enters into NA.  IF the MJO rolls into 8 and doesn't do the GMON stall in phase 7, that cold will likely get kicked southeastward.  That is why I am very interested in the next few days of MJO plots.  If they get to 8, even in the COD, that likely means the trough is in the East.

[Carvers Gap]

And there is more.  This is where the 12z GEFS left things at the end of its run.  That is a cold look with two mechanisms with which to send cold southward out of Canada - EPO ridge and blocking over Greenland.  And to get great winters, we need some SER.

[Carvers Gap]

The 18z RGEM is worth a look if you live in E TN from Knoxville northeastward and also the Plateau as this likely trends northwest.