December 2020 Medium/Long Term Pattern Discussion.

[Holston_River_Rambler]

EPS mean looks more like the OP overnight:

A question I have looking at this mean, is will the Surface Low try to jump to or at least toward the coast? I don't really understand the dynamic between a surface low and its upper level support. Sure, give me a normal shortwave on satellite and I think I could ball park where the surface reflection would show up, but this seems like it will be a unique lil beastie. 

I have a gif saved of a storm whose 500mb vorticity evolution reminds me of this one, but I won't say it out loud. The energy looked stronger with that one and it all came together further south. 

The 6z GEFS is still a west of the Euro, but seems to be getting a little closer to its solution, especially in the means as the storm develops and heads NE:

 

 

 

[Carvers Gap]

6z GEFS is a Miller B with energy transfer east of the mountains after it cuts.   0z EPS is more of an Apps runner with equal members on each side.  Still a ways to go.  As others have noted the energy behind that first system is very interesting.  BOTH the Euro and GEM operationals bring it up the Piedmont as a Miller A.  Still a lot of options on the table.  NE TN could score with the first storm even if the storm cuts as the storm has both upslope and wrap around....but it sort of has to be the same Miller B that DC scores with - meaning the energy transfers earlier.  The 6z GFS operational actually develops a lee side low, and that is one scenario for E TN.  Middle and western portions of the forum area have a real chance with system one.  TRI picks up 2-3" of snow with each system on the operational Euro.  It is a bit surreal to be tracking anything when one thinks of where modeling was (excluding the GEM) early last week.  LOL..

[Carvers Gap]

I should sat at met85 mentioned, the system early next week is a money set-up for upslope areas.  

[Carvers Gap]

6z GEFS snow mean (which has admittedly been a metric which has been absolutely worthless during the past two winters) has 4-6" of snow over E TN. The EPS is 2-3"  with more in the mountains...and an elevation dependent look.  I like to use NE TN as a benchmark, because it is easier to see if the storms are elevation dependent - and it is close.  

One interesting note in the LR, both the GEPS and GEFS have moved to a cleaner ridge out West which is more of a -EPO(GEPS is both PNA and EPO ridge)...but the interesting thing is they pull the trough back.  The EPS pretty much holds the upcoming pattern in place.  My thinking(and it could be wrong) is that if we can get the EPO ridge after the PNA(due to retrograding), that we might be able to squeeze another week or two out of the pattern.  If the GFS and GEPS verity later in the run, that is a very stable look and not as wonky as the upcoming first two weeks of winter.

JB has noted that he thinks the pattern flips to an eastern ridge prior to Christmas due to the MJO...well, plus that fits their seasonal forecast.  The Weeklies on Monday did sort of fit that idea, but they IMHO really didn't lock that eastern ridge into place.  Right now, I think LR forecasting is not for the faint of heart as this early Dec pattern resembles more of an El Nino(trough in the SE) than a Nina.   I do think because we are getting this early chance, that opens the door for 1-2 more windows later this winter...but who knows.  

[Holston_River_Rambler]

I saw that MRX overnight mentioned the WPC and hadn't looked at their maps yet:

 

not unhappy with that look 5 days out. 

[John1122]

12z modeling suite so far features a definite southward trend away from cutters. If we keep it up we might end up with a slider/Miller A. 

 

The Canadian mauls the mid-state. 

 

[Carvers Gap]

29 minutes ago, John1122 said:

12z modeling suite so far features a definite southward trend away from cutters. If we keep it up we might end up with a slider/Miller A. 

 

The Canadian mauls the mid-state. 

 

Ditto.  Yeah, take a look at the Canadian at 500 after d5.  PNA on steroids.   If that verifies, going to be tough for anything to cut after the first storm, and it may not either.

[Carvers Gap]

Man, the 12z Euro...that is a whopper of a storm.  I would be licking my chops in middle TN.  Wow.  Foot totals on the Plateau.  Two foot totals in central KY.

[Carvers Gap]

...And if that is even the slightest over amped, that is coming east some.  What a storm on that run.

[Carvers Gap]

And another storm comes right after it which gets suppressed by the massive NW flow - the first storm almost acts like a southerly displaced 50/50 low.  That could verbatim get places in our southern reaches some frozen stuff.  

[Holston_River_Rambler]

EPS still looking good and even a little east of the OP

[Holston_River_Rambler]

 

[Carvers Gap]

2 minutes ago, Holston_River_Rambler said:

EPS still looking good and even a little east of the OP

That is an inland runner right there.  Looks like very little energy transfer.

 

[Holston_River_Rambler]

Precip and 850 temps too nice not to share too 

sorry for multiple posts but trying to do all this from my phone now 

[PowellVolz]

This is getting interesting


.

[Carvers Gap]

12z EPS is an inland runner with the main cluster running from just west of Columbis, SC, to DC.  There are solutions on either side of that FWIW, but looks every so slightly east of 0z and 6z off the top of my head.

[John1122]

If we can pull this off, we are seeing the power of the Pacific blocking and how important it is for winter weather here. It's really really tough to get anything without it. But when we get it and it's oriented correctly, look out.

Eric Webb earlier said it looked like a typhoon was trying to form in the Western Pacific in an area that would potentially prolong the +PNA pattern we are looking at now.

The Euro also extended the snow shield westward that run, creeping it closer to the Mississippi.  Plenty of potential from that suppressed following wave too.

[John1122]

The Canadian Ens are just beefy for the next two weeks outside of far western areas. Really big for the mid-state and east areas, Kentucky and SWVA.

[PowellVolz]

From MRX:

“So in closing, confidence is quite high that the higher terrain
areas will see snow during this event; how much is still to be
determined. The valley is much more uncertain as was mentioned
earlier. I will say that if recent runs of the ECMWF are correct
that there is a very good chance that most valley locations will see
some snow and perhaps even some light accumulations. However, there
are just too many uncertainties at this point to get any more
specific with the forecast. Bottom line, please stay tuned to the
forecast because this system has the potential to bring snow across
much of the area but the uncertainty is very high across the lower
elevations.”


.

[tnweathernut]

10 minutes ago, PowellVolz said:

From MRX:

“So in closing, confidence is quite high that the higher terrain
areas will see snow during this event; how much is still to be
determined. The valley is much more uncertain as was mentioned
earlier. I will say that if recent runs of the ECMWF are correct
that there is a very good chance that most valley locations will see
some snow and perhaps even some light accumulations. However, there
are just too many uncertainties at this point to get any more
specific with the forecast. Bottom line, please stay tuned to the
forecast because this system has the potential to bring snow across
much of the area but the uncertainty is very high across the lower
elevations.”


.

That’s bold wording from MRX, for a system this far away.  Generally they are extremely conservative, sometimes even as inches of snow are falling around the region.

[John1122]

It's a tough one for MRX, as much of the modeling is showing significant accumulation differences in the central/south valley areas with the Euro going in for even the valley area and the Canadian and GFS showing the classic valley wedge from Chattanooga to Knoxville. 

[John1122]

The ICON only goes out to 120 hours at 18z and it looks like Tennessee would be under the comma head from the system. It's pouring snow on the Plateau/Eastern Rim as the LP is moving across NC at the end of the run. We finally saw a rain to accumulating snow event work out last December. They had been common for most of my life before the 2000s but have gotten rare since.

[Carvers Gap]

18z GFS is similar to 12z....the overall expanse is the storms is much bigger.

[1234snow]

Very surprised that MRX has accumulating snow wording already for a system next week. That is a rarity for sure.

I hope that everyone has a great Thanksgiving! I’ve been reading and lurking in the background.

Pleasantly surprised that we already have multiple chances to track over the next few weeks. I did not expect that at all. I figured we would continue the wall to wall warmth straight out of our warm fall into most of winter with minimal cold shots.

The atmosphere seems to be acting like a Nino instead of a Nina for the next few weeks. Give me some high latitude blocking potential, +PNA, and an active subtropical jet and we will surely score one hit in December.

[Carvers Gap]

@nrgjeff, what are your thoughts on the Euro Weeklies?

[Wurbus]

GEFS snow mean looked juicy!

[Save the itchy algae!]

2 hours ago, Wurbus said:

GEFS snow mean looked juicy!

How dare you say that and not elaborate! Perma ban for you!

[John1122]

8 minutes ago, Save the itchy algae! said:

How dare you say that and not elaborate! Perma ban for you!

Here you go. 

 

 

[Wurbus]

56 minutes ago, John1122 said:

Here you go. 

 

 

Thanks John. I was just on my phone looking and saw it earlier.

[Carvers Gap]

0z GFS is rolling....probably still going to see 2-3 more runs of volatility and then see models begin to lock-in by early Saturday.