December 2025 Short/Medium Range Forecast Thread

[Carvers Gap]

I haven't talked a ton about the d10-15 today, but modeling is MUCH colder with it.  The 18z GFS is frigid.  Its ensemble isn't much warmer.  The EPS at 12 was cold.  I think the MJO juice has made it to the deterministic models and their accompanying ensembles @Daniel Boone!  The juice is loose!

[Carvers Gap]

4 hours ago, nrgjeff said:

This system will probably do more than Monday night Tennessee north of I-40. Not everywhere, but more places esp northeast Tenn.

More I mean snow. Fortunately the ice looks trace again. Regrettably I don't have time to write more. Good luck up there!

You all are keeping the lights on which we appreciate greatly!!!!

[Daniel Boone]

4 hours ago, John1122 said:

It looked like Maine or somewhere here in 1996. There was snow piled up to the bottom of stop signs and in mountains in parking lots from Early January until around Valentines Day.

Same here John. I lived in downtown Pennington gap then at an Elevation of just 1360 and recorded 52 inches for the Season. Much of the Area received more due to Elevation. Wise set State Seasonal Record with 123.4 inches.

[Carvers Gap]

The 6z GFS might be its coldest run yet.  The 0z Euro and CMC have several light events which are northern stream driven.  Models continue to get colder.

[Carvers Gap]

The GFS has had this time frame(give our take a couple of days from Dec 17th) on-and-off as a potential time for very cold air.  The 0z Euro also has this but just a bit shallower.  The extreme solutions have not verified yet, but only IMHO because climatology really hasn't supported it yet.  By mid-December, very cold air has precedent over the valley regions.   This also fits recent MJO rotations - I have not looked a today's as of this post.

Again, if you like nickel and dime events(sometimes w/ mixed precip), the next 2-3 weeks are full of them.  Let's see if they verify.  Right now the trough axis is slightly too far to the East.  Where is the actual SER when you need it, right?  

[Daniel Boone]

After the shafting we Tennessee Valley Folks got from this one hopefully we get lucky with the other's up the pipeline. I had a light dusting from this one. Blacksburg about 5". Even Danville at about 800ft elevation in South Central VA near the NC Line has 3" and still snowing.

[Carvers Gap]

1 hour ago, Daniel Boone said:

After the shafting we Tennessee Valley Folks got from this one hopefully we get lucky with the other's up the pipeline. I had a light dusting from this one. Blacksburg about 5". Even Danville at about 800ft elevation in South Central VA near the NC Line has 3" and still snowing.

I think the next "system" will be Sunday night.  The 12k NAM has it as does the RGEM.  it is coming in at night.  If the NAM is correct, that could be minor to moderate upslope for the Plateau and maybe the Apps. 

The MJO is a "choose your own adventure" this morning at CPC.  It has yet to loop back around.  But....the GFS and Euro now show it stalling in 8 - and I am still not sure that actually happens!  If it actually stalls in 8 for a long period of time(and it is already halfway across 8), that would leave the door open for very cold temps.  I almost kind of wonder if the CFS has it right.  It trucks across the cold phases, rolls through the COD to 6, and then goes back through the cold phases again.  That looks an awful lot like those CHI graphics Jax recently posted.  Strong 1-2, strong Maritime, continues to dateline.  I do think we have a cold shot coming mid month...we'll see if I am right!  LOL.

[jaxjagman]

Not sure the MJO is really stalling out,its during the next few days the signal is getting nothing but constructive interference from Kelvin.Rossby.CFS has been showing this for several days now

[Carvers Gap]

The 12z Euro is frigid w/ a couple of days of real feels that have below zero readings.  Both the 12z GEFS and GEPS ensembles show cold temps some time between Dec 14-17th.  I suspect we see an anafront(a constant them of mine I know) at some point in that time frame.  I think we could see 1-2 very cold air masses push through the area mid-month.  And honestly, all of us would probably appreciate some moderation if those come to pass.

[Carvers Gap]

The 12z GEFS has temps twenty-five degrees below normal in WI at 195 w/ all of that headed SE.  During that same hour, our forum area has departures of fifteen degrees BN.  That is frigid for an ensemble at this range. The 12z GEPS is even colder over our forum area w/ temps 20 degrees BN over much of the area. The GEPS brings another cold shot around the 21st.  

The 12z EPS is rolling.  It has the same cold shot, and is a bit "warmer."  It is only 10-15 degrees BN.  That is cold for a model w/ a bit of a warm bias in d10-15.

Short story, even at this range, there is a growing likelihood of very cold air making it to our latitude by mid-month.  Both the GEPS and AIFS ensemble(to some extent), show the second cold shot around the 20th.  With so much snowpack immediately to our north, these cold air masses are on greased skids.

[Carvers Gap]

Just looking at northern hemispheres modeling, the coldest air on the planet will likely be over the Yukon d8-15 roughly.  The mechanism to deliver that into the Upper South is present in the forum of a flat western ridge.  The colder of the air (for now) will slide across the upper MidWest and into the NE.  HOWEVER, any kind of cutter or storm which gains latitude could send all of that into the Tenn Valley region.  Both the 6z GFS and 12z Euro have minor slp events which do it.  I cannot imagine what a big storm would wrap in.  A portion of the TPV is basically parked over the Hudson Bay, and just pinwheels cold air southward. In other words, we have a trough modeled.  The source region for that trough is very cold air.  Remember these winters where NA was void of BN air...not this year!

[Carvers Gap]

I mentioned 95-96 yesterday.  Interestingly, the d8-14 analogs have that analog(I didn't see it until today FTR).  I am glad not to see 83-84 in that mix!  Dec 2012 is double weighted as well.

19951129
20161209
20121128
20221129
19961223
20101212
19951204
20211222
20121203
20081231

[jaxjagman]

22 minutes ago, Carvers Gap said:

Just looking at northern hemispheres modeling, the coldest air on the planet will likely be over the Yukon d8-15 roughly.  The mechanism to deliver that into the Upper South is present in the forum of a flat western ridge.  The colder of the air (for now) will slide across the upper MidWest and into the NE.  HOWEVER, any kind of cutter or storm which gains latitude could send all of that into the Tenn Valley region.  Both the 6z GFS and 12z Euro have minor slp events which do it.  I cannot imagine what a big storm would wrap in.  A portion of the TPV is basically parked over the Hudson Bay, and just pinwheels cold air southward. In other words, we have a trough modeled.  The source region for that trough is very cold air.  Remember these winters where NA was void of BN air...not this year!

Strong blocking into the Western Aluetians,Bearing Sea being shown would pump up a +PNA but where does the Trough Axis set up,definite cold look towards the Mid month