December 2022 Medium/Long Range Pattern Discussion Thread

[John1122]

That GFS run is a major winter storm for us all. It's legendary for underdoing precip shields for gulf lows, often having them hundreds of miles South of the area where they verify. A LP in that spot at that strength usually has a good precip shield up to Lexington. 

That said, suppressed at range is always better. That's assuming you can trust the gfs at all, which is a big assumption. 

[John1122]

The Canadian has the first storm the GFS is showing but squashes soon after it gets going in the gulf. 

[Daniel Boone]

2 minutes ago, John1122 said:

That GFS run is a major winter storm for us all. It's legendary for underdoing precip shields for gulf lows, often having them hundreds of miles South of the area where they verify. A LP in that spot at that strength usually has a good precip shield up to Lexington. 

That said, suppressed at range is always better. That's assuming you can trust the gfs at all, which is a big assumption. 

Yeah, was just looking at that. Man , if that comes to fruition, white Christmas would be likely with locked in cold . 

[fountainguy97]

I'm not going to lie. All I see is models kicking the can down the road. Nothing concrete has moved into the more confident short range or even mid range.  
 

Our first two storms (front passage and suppressed wave behind it) have gone their way. Third one already pretty far north on guidance. 06z gfs continuing that trend.   Really hope we don't kick the can in these threats straight into spring. 

[Holston_River_Rambler]

There's definitely been can kicking, but I think some of that gets settled, at least with regards to the pattern, once this huge cut off upper low gets out of the way over this next weekend. 

I really wish we could have gotten some upslope this weekend though since I'm going to be in Boone. Upslope is a pretty hard one to screw up, even for our area, so I'll call that a can punt. Its reminiscent of a certain infamous punt from the GA TN game this year. 

[Holston_River_Rambler]

6z GFS has re introduced the idea of some upslope this weekend, Euro has the vort that causes it on the GFS too, but doesn't show any precip. Maybe we can squeeze out a snow shower or two?

[Carvers Gap]

In regards to early season storms, we have been playing with house money in E TN for the past decade or so.  Climatology doesn't really support snow here until late December.   On the flip, Nina does support colder Decembers here.  So far, everything we are seeing is fairly text book La Nina...dry fall(drought, followed by rain increasing during winter, cutters on modeling which favor middle and western forum areas,,,,

For E TN to score, we need the cold to continue to press eastward.  The Greenland block "should" support storms going to our south.  Then, it is just a crapshoot as to where it curves northeast(if it does at all).  Lots of solutions available in modeling still.  The cold pattern is about 8 days later than originally modeled, but it is on it way it appears.  I think the real action occurs is when the PNA pops out west in conjunction w/ the NAO.  Oddly, we need to see the SER flexing its muscle just enough.

[Jed33]

20 minutes ago, Holston_River_Rambler said:

6z GFS has re introduced the idea of some upslope this weekend, Euro has the vort that causes it on the GFS too, but doesn't show any precip. Maybe we can squeeze out a snow shower or two?

Fwiw the CMC from 0z has the upslope this weekend as well.

[Carvers Gap]

The 6z GEFS(all caveats apply),  0z EPS, 0z CMC, and CFSv2 are showing temps 20+ BN around Christmas.  Impressive to have that ten days out on ensembles.   Would not surprise me to see middle and west TN well into the single digits.  E TN will get quite cold as well.  IF the SER flexes into that air mass....look out.

[Carvers Gap]

Again, I would be chomping at the bit if I lived along (and northwest of) a line from Memphis to Nashville.  That said, that doesn't rule out winter wx in E TN.  The track around Dec 20th will need to be watched - slider city if it comes northward.  It is suppressed right now, but that could change.  All caveats apply for our subtropical latitude.

I think the possibilities of an overrunning event are still there.  "Where" is the question

[Daniel Boone]

3 hours ago, Carvers Gap said:

In regards to early season storms, we have been playing with house money in E TN for the past decade or so.  Climatology doesn't really support snow here until late December.   On the flip, Nina does support colder Decembers here.  So far, everything we are seeing is fairly text book La Nina...dry fall(drought, followed by rain increasing during winter, cutters on modeling which favor middle and western forum areas,,,,

For E TN to score, we need the cold to continue to press eastward.  The Greenland block "should" support storms going to our south.  Then, it is just a crapshoot as to where it curves northeast(if it does at all).  Lots of solutions available in modeling still.  The cold pattern is about 8 days later than originally modeled, but it is on it way it appears.  I think the real action occurs is when the PNA pops out west in conjunction w/ the NAO.  Oddly, we need to see the SER flexing its muscle just enough.

Yeah, Nina has really been ruling the Roost. If blocking can hold strong enough we should get some low road systems. 

      Agree on PNA as well. That would put the icing on the Cake. Seems it's like pulling teeth to get a -NAO +PNA Combo anymore.

     A big worry too is once the cold settles in ,we go bone dry. I remember the super cold Christmas '83 out break doing just that. Not a single flake ! A High of zero that day in Pennington gap with bare ground. Unreal !

     Get this, 2 days later a southern Ms Valley System moves in starts as Snow, coats the ground with a heavy dusting and then suddenly turns to Rain. Storm cut west. 

[John1122]

12Z GFS is full 1983. The December of ultimate frustration as Daniel noted. That year we'd get cutters, then ice box cold. Looks like single digits and low teens in the afternoon on Christmas Eve after a rain to snow front this time out. Sounds like 2020. Major cold, but once again, GFS at range is not reliable so far.

[snowmaker]

A question for Carver and others with good weather knowledge. Could the snowpack to our northwest help with the push of arctic air or at least keep the air from modifying as quick as advertised at times on modeling? And do models sometimes struggle with arctic air masses as the come south, especially ones that have a good snowpack to our northwest? Thanks in advance.

[Coach B]

1 hour ago, John1122 said:

12Z GFS is full 1983. The December of ultimate frustration as Daniel noted. That year we'd get cutters, then ice box cold. 

Ugggh..... Nashville only reached 40 degrees once during the 1983 holiday 9 day arctic plunge. You guessed it.... it rained over an inch that day and other than some token flakes/dustings it was basically bone dry and frigid the rest of the time. I think most of the state got a couple of events during January 84, but the repeated cold/cutter combo had to be painful during that period. 

[Carvers Gap]

So the take away from 12z so far is this.....Remember when the polar vortex got trapped under the block, but modeling lost it?

[Carvers Gap]

38 minutes ago, snowmaker said:

A question for Carver and others with good weather knowledge. Could the snowpack to our northwest help with the push of arctic air or at least keep the air from modifying as quick as advertised at times on modeling? And do models sometimes struggle with arctic air masses as the come south, especially ones that have a good snowpack to our northwest? Thanks in advance.

Yes, that is correct.  The further that snow pace gets, the colder that air is gonna be.  @John1122 is that a record high pressure over Montana if it verifies?

[Carvers Gap]

2 hours ago, Daniel Boone said:

Yeah, Nina has really been ruling the Roost. If blocking can hold strong enough we should get some low road systems. 

      Agree on PNA as well. That would put the icing on the Cake. Seems it's like pulling teeth to get a -NAO +PNA Combo anymore.

     A big worry too is once the cold settles in ,we go bone dry. I remember the super cold Christmas '83 out break doing just that. Not a single flake ! A High of zero that day in Pennington gap with bare ground. Unreal !

     Get this, 2 days later a southern Ms Valley System moves in starts as Snow, coats the ground with a heavy dusting and then suddenly turns to Rain. Storm cut west. 

You know...it doesn't show much sign of letting up.  I keep looking for a thaw.  Right now, a thaw might be just getting back into the 50s.  If the GFS/CMC get anywhere near to verifying, that would freeze rivers.  If we managed snow on the front end...it isn't going anywhere.  The surprise in all of this is seeing the PNA begin to rule the roost (had to borrow that term...) longer term.  That is a very cold North American pattern showing up.  

Remember when all of us were like, "Where is the cold air with that much blocking up top?"  There it is.

And extreme cold shots are certainly part of the Nina toolbox for sure.  It could certainly go dry.  The recent pattern has been drought until last week.  I would not be shocked to see an EC blizzard at the front end of this pattern or as it relaxes.  

[tnweathernut]

5 minutes ago, Carvers Gap said:

So the take away from 12z so far is this.....Remember when the polar vortex got trapped under the block, but modeling lost it?

I kinda hope that DOESN'T come down the front range of the Rockies............ eek.

 

[Carvers Gap]

Just now, tnweathernut said:

I kinda hope that DOESN'T come down the front range of the Rockies............ eek.

 

It comes down the front range and heads eastward....pipe buster right there.

[Carvers Gap]

1 minute ago, tnweathernut said:

I kinda hope that DOESN'T come down the front range of the Rockies............ eek.

 

There are snow showers over the central GOM later in that run.

[beavis1729]

8 minutes ago, Carvers Gap said:

So the take away from 12z so far is this.....Remember when the polar vortex got trapped under the block, but modeling lost it?

Yikes...that would shatter the Lower 48 high pressure record (1064mb in Miles City, MT 12/24/1983).

[Carvers Gap]

The 12z CMC does have a decent set-up.  If one buys that the GFS has a progressive nature(IDK w/ the new upgrade), the CMC looks like a decent compromise.

[Carvers Gap]

The CMC has a 1060hp coming south around 204 in the NW Territories.  Those are some big numbers for highs and gives us a sense of what modeling is "seeing" at 12z.  With wild swings in modeling, I have no idea if this holds....but there is certainly a mechanism in place to drive that cold all the way to the GOM w/ the double block in place.

[Carvers Gap]

Check out Greenland(-65F) late in the CMC run.  I told ya'll that you needed to sign a waiver....

 

[Met1985]

Yeah great analysis guys. Possibly record breaking pressure,  record breaking cold, and lots of moving mechanisms for this pattern to take place. Storm or no storm the cold is going to be around. But as many have mentioned is the tendency going to be more Nina like or are we going to be getting in on the action equally.  Questions,  questions. 

[John1122]

24 minutes ago, Carvers Gap said:

So the take away from 12z so far is this.....Remember when the polar vortex got trapped under the block, but modeling lost it?

I believe 1064 is the record for the lower 48.

[Carvers Gap]

Evidently, the CMC is gonna require paperwork as well for viewing....Departures from normal on the 23rd.  This is what happens if a storm deepens to our east.  ALL of that cold heads our way.

 

[Carvers Gap]

18 minutes ago, beavis1729 said:

Yikes...that would shatter the Lower 48 high pressure record (1064mb in Miles City, MT 12/24/1983).

1 minute ago, John1122 said:

I believe 1064 is the record for the lower 48.

Thanks, to you both.  Man.

The CMC had a similar number in Canada.  

[Met1985]

3 minutes ago, Carvers Gap said:

Evidently, the CMC is gonna require paperwork as well for viewing....Departures from normal on the 23rd.  This is what happens if a storm deepens to our east.  ALL of that cold heads our way.

 

Good Lord we've not seen temps this cold in several years in the region here. Personally I could do without that. 

[Carvers Gap]

1 minute ago, Met1985 said:

Good Lord we've not seen temps this cold in several years in the region here. Personally I could do without that. 

The source region at 12z in Canada is very cold.  We have had those beautiful blocks up top on modeling for weeks, but the source regions was not great.  Now, the source region is cold, even by Canada's standards.  I was looking at an animation of the CMC(could have been the GFS) late in the run (n hemisphere view) where the cold is just pouring over the pole into North America from a very, very cold Asian continent.