December 2020 Medium/Long Term Pattern Discussion.

[Holston_River_Rambler]

This time weathermodels had all snow too. 
 

[John1122]

The Christmas time frame has shown up on the GFS a few times too. Looked like anafrontal snow showers. Oddly those have produced two years in a row for me now when not much else has. 

[Windspeed]

This is a pretty big deal and thought it should go here.

[Holston_River_Rambler]

Not much more than a curiosity, but the NAM, RAP, and HRRR show some snow trying to move up I-40 from Memphis towards Nashville tomorrow AM between 7 AM and 10 AM central time. 

The NAM is the least interested, but ti still has a brief window, and here is it's sounding:

The Euro shows some mixed precip, but not much more. I'm betting too little too late, in terms of cold chasing moisture, but will be watching when I wake up tomorrow to see if anything like this happens. 

 

Here is the latest HRRR, for full snowy, and probably overdone, effect. 

[John1122]

7 minutes ago, Windspeed said:

This is a pretty big deal and thought it should go here.
 

I'm approaching 100 inches this year but probably won't quite get there although the GFS has me pretty close with some of it's big totals showing up. Though technically I'm partly in the Cumberland river basin.

[Carvers Gap]

D9+...12z EPS has basically a double block. EPO and Atlantic. 

[Carvers Gap]

The 18z GEFS hammers NC with two storms.  The first is nearly perfectly placed and if real, would also likely hammers E TN.  There is a second right after it.  If one takes the progressive GFS at its word, that is right where we want both storms.  Certainly laid down the gauntlet.

[nrgjeff]

Following up on the record TVA rainfall...

Christmas looks like cold chasing rain! What's new around here? Could be worse. At least Christmas should be sunny on northwest flow.

Cynical negativity aside, variability may continue into January. Looks like even if New Years warms up, another shot of cold is likely the following work week. 

Key is to keep getting cold shots deeper into January and hope something lines up. I share Carver's cautious pessimism, but there's still hope. It's early.

[Carvers Gap]

Low confidence.  At this point today, just not seeing anything but a "thread the needle" scenario for snow.  CFSv2 shows some hope after week one, but not holding my breath.  Trends during the past 24 hours have been towards a big ridge building in after Christmas - surprise!  Total flip.  Big amplification around Christmas, and almost immediately replaced by a ridge.  Better than a torch and not really hostile to snow...but not really anything that looks as awesome as a couple of days ago.  Pretty sure a good church of those runs was a mirage - may come back later, but 12z looking rough.  

[Wurbus]

I think we need a Christmas miracle!

[Holston_River_Rambler]

Well the good news is, we’re not in any bulls eyes for the 24 or 25th yet, so it can’t trend to severe yet. 

[John1122]

I suspect we will at least see snow showers and snow flurries on Christmas. It's a straight up Arctic airmass and it will wring out moisture.

I'm also convinced it will snow/rain/be cloudy in general on the 21st too. Ever since the perfect eclipse weather I've been cloudy or precip has been falling for every celestial event. I had a seemingly endless evening cloud streak trying to see Neowise.

[Holston_River_Rambler]

I think Happy Hour GFS is about to create some wonky bizarro storm. Dropping energy over Cabo San Lucas after Christmas. 

[Holston_River_Rambler]

Gives our N. areas a nice overrunning event, but that piece of energy over Cabo just gets stuck. 

Two big highs drop down through hr 280:

 

 

 

 

[Holston_River_Rambler]

I think one of the reason some of the longer range looks have seemed to go downhill a little (as I look at 500mb heights on the same GFS post hour 300), may have to do with a convection flare up, north of the equator, over the ever popular MJO regions 5 and 6:

 

Compare to a few days ago:

 

 

[BNAwx]

I’m sure reality will prove me wrong when it’s all said and done but it seems like the base state this year is to be average or cooler than normal.  Projected warms ups are somewhat muted in the long range.  Last year, it was the opposite.  We kept expecting cold to take over but it never panned out.  The MJO screwed us over last year and never looked back.  
 

I hope this is one of those rare years where the NAO and AO regions continue to cooperate. Over the past few years, a Bigfoot sighting is more likely than those two indicies lining up.  Maybe we’re finally due.

 

[Wurbus]

CMC had an odd run. Develops the low along the front around Christmas and it comes up through east TN. I would think middle TN would score with that look. Although, at this point, it is an outlier.

[John1122]

The Euro cooks up something for Christmas eve as well. It's not the epic bomb that was the Canadian but it throws out some biting cold and anafrontal snow due to the strength and speed of the Arctic air mass. There's hardly even any rain, most of the precip except for the very leading edge is frozen. The Euro ends up here and it may be higher with ratios. Many of us would have a shimmering blanket on Christmas morning. Not much of any melting either as temps go from single digits and teens into the low to mid 20s to lower 30s.

[weathertree4u]

1 hour ago, John1122 said:

The Euro cooks up something for Christmas eve as well. It's not the epic bomb that was the Canadian but it throws out some biting cold and anafrontal snow due to the strength and speed of the Arctic air mass. There's hardly even any rain, most of the precip except for the very leading edge is frozen. The Euro ends up here and it may be higher with ratios. Many of us would have a shimmering blanket on Christmas morning. Not much of any melting either as temps go from single digits and teens into the low to mid 20s to lower 30s.

The Canadian has a similar setup but favors more of a west - middle TN area  

[John1122]

06z GFS was more progressive with the cold front blasting through the state around the 23rd into early Christmas eve. Then frigid air rushes in and wrings out what would be fluffy snow to the tune of 1-3 high ratios inches over parts of the area as temps crash through the 20s into the 10s. 

 

12/1PM temps Christmas day

 

[John1122]

The 00z GFSv16 put this out for Christmas Eve/Christmas as it's finally coming into Pivotal. It's actually sort of inline with what the Euro shows. Much warmer than the 06 GFS in the wake of the snowfall though.

[John1122]

And for people who like to just check here. That Canadian mauler that stalls the Arctic front and lets a low ride the front that thumps the middle valley areas then changes to snow in the East as the Arctic air continues to invade. In circumstances like this with that nice a cold air source. I've found the cold usually bleeds further east than modeled.  I'd love to see this one be the one that comes to pass because it really works out for the entire forum.

This is about mid-event. It hammers western areas before this and further eastern areas get in on the action after this.

[weathertree4u]

1 minute ago, John1122 said:

And for people who like to just check here. That Canadian mauler that stalls the Arctic front and lets a low ride the front that thumps the middle valley areas then changes to snow in the East as the Arctic air continues to invade. In circumstances like this with that nice a cold air source. I've found the cold usually bleeds further east than modeled.  I'd love to see this one be the one that comes to pass because it really works out for the entire forum.

This is about mid-event. It hammers western areas before this and further eastern areas get in on the action after this.

Next couple of days this system should come into better focus in the modeling but already appears there is at least some agreement of some type of system next week followed by colder temps.

[Holston_River_Rambler]

All three have the main piece of energy, and have for a few days, just a question of how the interaction happens. Like y'all said, the CMC was a beut!

A full on triple phaser (and about to be quadruple phaser over NE):

The main piece drops across the Bitter Route range along the MT/ ID border.

GFS:

 

Euro:

That little extra piece of energy that the CMC has coming across Northern CA, both the GFS and Euro snip it off over the Pac, and that piece seems to be the key to the CMC's big dog. 

 

Some of the new 6z GEFS members have low popping on the front:

 

The EPS has a few too. 

[Carvers Gap]

Any good trends with overnight model runs?

[PowellVolz]

Any good trends with overnight model runs?

Lol...


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[Carvers Gap]

To say that LR modeling is all over the place right now...might be an understatement.  Huge swings over our region from run to run.  Consistent(using that term loosely) features seem to be a -NAO...man, that might be about it.  LOL.

[PowellVolz]

To say that LR modeling is all over the place right now...might be an understatement.  Huge swings over our region from run to run.  Consistent(using that term loosely) features seem to be a -NAO...man, that might be about it.  LOL.

I’d rather see that than a big fat SER being shown for weeks because we all know the mods are probably not going to be wrong showing a strong SER.


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[Daniel Boone]

5 hours ago, weathertree4u said:

Next couple of days this system should come into better focus in the modeling but already appears there is at least some agreement of some type of system next week followed by colder temps.

Just place that solution 100 miles further East and we'd all still be fine.

[Wurbus]

Looks like CMC holds the energy back a little bit and it winds up phasing a little later. Not as big as a hit for mid/west TN as the last run. Looks like East TN gets some wrap around snow as the low travels up through East TN again.