December 2020 Medium/Long Term Pattern Discussion.

[Carvers Gap]

3 hours ago, Holston_River_Rambler said:

I've seen fantasy Greenland blocks before, but don't think I've ever abv. normal heights over Greenland one for almost an entire run. 

Have you looked at the spv/tpv at that time?  Has to be something going on....to really crank that.  It(-NAO) is showing up on multiple models as well, even the ensembles are having to dig for new colors.

[TellicoWx]

Think we are starting to get somewhat of a solution...compromise between the progressive bias of the GFS and the overamping bias of the Euro (seems to have gotten worse since the upgrade, esp at mid range)...a weak southern slider, that has some boundary layer issues. Wouldn't be surprised to see the final solution be a 1-3" swath somewhere across the Mid south.

[BlunderStorm]

I noticed on the latest GFS run the first system that rolls through the midwest is more progressive perhaps introducing less cold to the Tennessee Valley in time for the second system. Another possibility is that with a stronger second system sporting a more defined center of low pressure it acts to warm up the valley without an area of high pressure to the NW reinforcing colder temps. If we were looking at more of a semi Miller A setup like we saw with the Euro last night perhaps it would be manageable for at least the eastern regions but this does not look to be the case with the euro biases and trend as of the 12z run. Instead echoing what Tellico said we may be looking at a weak to marginal slider with potential for snow in high elevations and maybe some lucky areas along I-40 and north. As a side-note the Canadian seems to be in general agreement with the GFS. In the meantime will see what the Euro has to say. On the bright side it would seem we will likely see multiple opportunities as December progresses and the effects of a -NAO and -AO really start to kick in. (fingers crossed)

[Carvers Gap]

GFS and Euro both have Monday's system back.  As Tellico noted, it is weaker but looks like a good compromise.  That said, it is never out of the question that modeling could trend back to nothing or even trend stronger.    Time of day would be important.  LR, still a lot of uncertainty.  It is less certain that it will be warm from Dec 18-30 than it was 4-5 days ago.  But, it is no slam dunk for cold either.    Kind of a fun time of year.  Nothing huge for sure, but would not surprise me to see a really amped system at some point either.  After last winter where it was just one disappointment after another and then finally went warm, "uncertainty" is not a terrible outcome in LR modeling or even short range.  Gives everyone a chance to hone their skills, and maybe reel one in.  Kind of like this...better fishing in a lake that has fish than one that does note(comparing this year to last year).

[Holston_River_Rambler]

6z RGEM looks tasty at it's end:

If it can dig a little more and separate from that N. Stream, piece it is in sync with, it would help. Otherwise it might get squished.

 

I think if we can get a healthy vort rolling along I - 20, it may surprise with it's precip shield. But look at how differently the energy is still being handled:

6z GFS, southern stream looks similar, but a totally different depiction of the N. energy from the RGEM:

 

0z Euro looks more like the RGEM:

 

and the 6z NAM  just looks like as mess:

 

Agree with y'all overnight and I think everything from the high end of Tellico's call above, to Blunderstorm's weak slider are still on the table this AM and the 0z EPS city charts show that for most areas in our forum. 

[Holston_River_Rambler]

@Carvers Gap

In terms of the strat, there is definitely a solid attack at it's base (look at the top of Greenland, it almost totally breaks at the bottom there) :

there's just not a lot going on above that. 

 

Most models show (still this AM) it getting split at 50 mb, and the main lobe dropping in over Hudson's Bay and then trying to reconsolidate, at that pressure level. At the top though, it stays pretty stout throughout, even if it is pushed around a bit. 

Here's the overnight Euro OP at 10 mb:

[nrgjeff]

Plateau and Mountains could have a fun 7-10 day period. GFS finally came around to King Euro with actual systems instead of weak fronts.

No cold air connection and warm boundary layer keeps most of the forum out of the game. Rain and 38 is good college sports on TV weather, lol!

Looking ahead, I'll just assume the EC weeklies will trend colder after Christmas like the CFS has. On the other hand the GEFS weekly product (separate from the CFS) keeps it warm. Anyway the CFS after Christmas forecast is colder than normal. We'll see if the blocking can overwhelm the on-fire MJO signal. 

My sentiment has shifted to mixed, from bearish, but I'm still not really feeling big cold. 

[Carvers Gap]

The 12z Euro puts TN back in the ballgame for the Monday event.  Super close call up this way.  Kind of has a sloppy look to it right now, but will have to keep following trends.  SLP placement is pretty much perfect for TRI, but cold is very marginal as evidenced by other deterministic models having cold rain.  Anyone know the time of day for that event?

I haven't seen the extended GEFS today(only comes out on the pay site after supper), but I like that model.  My only access to the GEFS extended has been this winter season.   At 500 yesterday, it didn't look all that bad.  Surface temps were lousy for sure.  One would think it would verify cold if the 500 look is real.  I looks at 500 maps and 850 temps as surface temps seem to be off lately.  

CFS almost seems too cold.  

Just don't cancel basketball season this year.  

[Carvers Gap]

The 12z Euro is flirting with another storm next Thursday.  Entry angle into the SE is decent for a slider(but watch it cut...if it does, sorry for the jinx).

[Holston_River_Rambler]

I'm starting to become even more bearish than Jeff for the plateau, for the Monday deal:

Even though it is coming through overnight, and even though as Carver's mentions its a great low track, it's a rainer. Hopefully the energy can get a tad more wound up and pull a wee bit more cold in. Otherwise, it might just end up being a 3000 ft + event. 

[Holston_River_Rambler]

1 minute ago, Carvers Gap said:

but watch it cut...if it does, sorry for the jinx).

It has that wicked Miller B look to the setup. No bueno for me, but hopefully better for y'all up that way. 

[Icy Hot]

40 minutes ago, Holston_River_Rambler said:

I'm starting to become even more bearish than Jeff for the plateau, for the Monday deal:

Even though it is coming through overnight, and even though as Carver's mentions its a great low track, it's a rainer. Hopefully the energy can get a tad more wound up and pull a wee bit more cold in. Otherwise, it might just end up being a 3000 ft + event. 

Wishcast alert: Perhaps it will develop a couple hundred miles further south and round the pan-handle.

[Carvers Gap]

42 minutes ago, Holston_River_Rambler said:

It has that wicked Miller B look to the setup. No bueno for me, but hopefully better for y'all up that way. 

I am seeing a coastal near Charleston for that one and then runs up the coast.  Looks to me like the HP slide by a bit to quickly and we get the warm nose as the GOM feed punches into the Valley.

[Carvers Gap]

Actually, that second system has a great track, but just not enough cold.

[Carvers Gap]

Here are the maps from WxBell for the 12z Euro Deterministic:

Storm 1...continues after that slide as well 3-5 hour event if the model is to be believed for TRI - big IF.

Storm 1 accums...

Storm 2...You can see the SLP alone the coast.  Heads NNE right inside of Hatters.  There is a high sliding off just to the north of this screenshot.  Due to my mad copy and paste skills, I have cropped it out.

 

 

 

[Holston_River_Rambler]

@Carvers Gap I like weatherbell, now lol. Those surface maps look better than what I saw at weathermodels. They had a low in Kentucky for the second system, near Louisville, transferring to the coast. 

[John1122]

The Pacific being poor is just a killer. I'd take a favorable Pacific over the -NAO 8 days a week. Miller A rain event happen when the Pacific is bad. Wide spread winter is possible when it's good even if the Atlantic is bad.

[Holston_River_Rambler]

In the interests of dom (and because I saw it on the MA forum and it gave me the idea), I thought I'd look at the EPS MSLPs for the second system. More Miller Aish look. Still no guarantees it's not a rainer for people outside elevation (2500 ft. +) or SWVA and TRI, but, the more the low tracks S and E, the better for me. 

 

[Carvers Gap]

1 hour ago, Holston_River_Rambler said:

@Carvers Gap I like weatherbell, now lol. Those surface maps look better than what I saw at weathermodels. They had a low in Kentucky for the second system, near Louisville, transferring to the coast. 

I think with pretty vigorous winter storms, it is super common to have something go west of the Apps.  Just want the lion's share east.   

[Carvers Gap]

 

59 minutes ago, Holston_River_Rambler said:

In the interests of dom (and because I saw it on the MA forum and it gave me the idea), I thought I'd look at the EPS MSLPs for the second system. More Miller Aish look. Still no guarantees it's not a rainer for people outside elevation (2500 ft. +) or SWVA and TRI, but, the more the low tracks S and E, the better for me. 

 

Can kind of see the block at work there.   Looks like the system near Jacksonville slows and gets caught by a trailing piece of energy...then mini-boom phase.   Many Kocin storms have -NAOs.  You folks on the Plateau benefit far less with Atlantic blocking and do much better with Pacific.  We get a lot of Atlantic feed up here as you know.  If we didn't, I think we would be an almost arid region.  

John, what would be awesome is if the NAO can carry us until the Pacific gets a bit better - could bridge us between early December and mid-Jan.

[John1122]

If I were guessing most of the big  -NAO storms that hit eastern areas come when the Pacific is also favorable.  

The best temperature set up obviously comes when all three are negative.  But when the EPO is negative in conjunction with the AO, basically everyone in the South, west of Raleigh to Columbia is colder when the NAO is positive than they are when the NAO and AO are negative but the EPO is positive. 

So our ideal combination is -EPO/-AO/-NAO, followed by -EPO/-AO/+NAO, then +EPO/-AO/-NAO. 

We are rarely dry for long but it can happen. Getting cold is always our biggest step towards wintery weather Valley wide and it's much easier when the Pacific is working for us instead of against us. 

[John1122]

The weeklies had probably their snowiest run of the winter season so far. It wasn't spectacular but would represent something close to normal for most areas through January 25th. The snowiest 4 weeks we have are basically January 17th-February 14th so the Weeklies are just reaching there at the very end. 

It was around 4-6 inches in Eastern areas, 2-4 Western and southern areas. 

[John1122]

Ventrice also tweeted earlier that the Westerly OBO was beginning to affect the Troposphere and that could possibly weaken the MJO convection for a while. 

I've never researched it for here, but for Atlanta's winter events I believe GaWx found they mostly occurred when the MJO was in the C.o.D. Generally if Atlanta is having a shot at snow it's cold here and we've had it too. 

[Daniel Boone]

I've witnessed several decent snowfalls here over the years with a crappy Pac but, pretty much always a strong -NAO. 

    The 60'S come to mind as the -PDO La Niña Winters all had decent snowfalls. -NAO dominated those years.

[Carvers Gap]

1 hour ago, John1122 said:

Ventrice also tweeted earlier that the Westerly OBO was beginning to affect the Troposphere and that could possibly weaken the MJO convection for a while. 

I've never researched it for here, but for Atlanta's winter events I believe GaWx found they mostly occurred when the MJO was in the C.o.D. Generally if Atlanta is having a shot at snow it's cold here and we've had it too. 

Yeah, I noticed on some OLR maps that the warm phases  near the MC don't have high cloud tops in the LR which would likely mean less convection.  Also, the MJO looks like it may rotate quickly through 6(edit) and is aimed directly at 7.  If we can rotate through 7, 8, and 1 during late December, that would be cold I think.  

During a normal winter, I almost never really worried about snow prior to Dec.  You Plateau folks have different benchmarks!  LOL.  As a kid, I pretty felt like a 1-2" snow(in Knoxville during the 70s) was expected before early Jan.  I think this year with so many warm analogs(though once small cluster is very cold), folks feel like we have to get winter before mid Jan...and they may be right.  That said, it has been a while since we have had a cold winter.  So, we are sort of due.  But I will gladly take what the Weeklies are dishing out....well, until they get warm in mid Jan.   The torch on the Weeklies has been pushed back almost three weeks now.  Small victories!

[Carvers Gap]

49 minutes ago, Daniel Boone said:

I've witnessed several decent snowfalls here over the years with a crappy Pac but, pretty much always a strong -NAO. 

    The 60'S come to mind as the -PDO La Niña Winters all had decent snowfalls. -NAO dominated those years.

Since I have been doing this as a hobby, I am not sure I can really remember tracking many -NAOs.  LOL.  I have lived through -NAO winters, but have not tracked many.  Pretty much anything is better than last winter's tracking options.  For real, how many -NAO winters have we had since 2000?

[John1122]

52 minutes ago, Daniel Boone said:

I've witnessed several decent snowfalls here over the years with a crappy Pac but, pretty much always a strong -NAO. 

    The 60'S come to mind as the -PDO La Niña Winters all had decent snowfalls. -NAO dominated those years.

In the 1960s it snowed here no matter what it seems like. 

[Holston_River_Rambler]

18z Euro, oh Lawd:

 

[Daniel Boone]

41 minutes ago, Carvers Gap said:

Since I have been doing this as a hobby, I am not sure I can really remember tracking many -NAOs.  LOL.  I have lived through -NAO winters, but have not tracked many.  Pretty much anything is better than last winter's tracking options.  For real, how many -NAO winters have we had since 2000?

They're definitely fewer and further between than pre early 1980s. There's different hypotheses/theories on why. I think Wes Junker and maybe Anthony Masiello and some others discussed this pretty in depth several years ago on Eastern WB. Can't remember what their ideas were but, was interesting. 

     

[Carvers Gap]

33 minutes ago, Holston_River_Rambler said:

18z Euro, oh Lawd:

 

WxBell has snow north of 40 - heavy on the Plateau.