December 2020 Medium/Long Term Pattern Discussion.

[Holston_River_Rambler]

Dr. Schmaybe lives up to the name:

 

Looks more progressive a la the GFS. 

[Holston_River_Rambler]

Climo call for eastern TN  areas:

 

Moisture chasing cold. A slushy inch possible on grassy surfaces above 1500', higher accumulations possible above 3000 feet. Schmaybe mood flakes in valley locations below 1500'

 

[Holston_River_Rambler]

I don't think any one solution is a done deal yet. Individual impulses in the amplified flow will have a say. Still not much consistency IMO. 

[Met1985]

9 minutes ago, Holston_River_Rambler said:

I don't think any one solution is a done deal yet. Individual impulses in the amplified flow will have a say. Still not much consistency IMO. 

Same thing as I was thinking.  There has been no consistency at all for this storm. 

[TellicoWx]

1 hour ago, Holston_River_Rambler said:

I don't think any one solution is a done deal yet. Individual impulses in the amplified flow will have a say. Still not much consistency IMO. 

The two camps have been fairly consistent the last couple days at H5...12z I think signaled which camp is caving (Euro towards the GFS). Both have a spoke of energy rounding the flow at 12z (GFS just had more of a surface reflection)...that spoke is gonna vary probably all the way until 24-36 hrs from the start. When/if Ops start losing that, then we will trouble. Euro wasn't a hair from the GFS solution.

[Holston_River_Rambler]

4 minutes ago, TellicoWx said:

When/if Ops start losing that, then we will trouble.

Yup. I bet there will be a good NAMing though, before all is said and done, either way it falls out. 

[Carvers Gap]

Will keep it quick...Seems like models are narrowing down to a solution which will involve a wave running along a very strong cold front on Christmas Eve.  I have been using the term "low confidence" during the past few days.  Sometimes waves/weak slp along a front a money and sometimes not.  Super difficult to predict due to timing and location of the disturbance along the boundary in relation to our location.  For now, looks to me like a strengthening area of slp will slide through western North Carolina.  Normally, that track is bad mojo for E TN.  With the cold air modeled to quickly rush into the region, there is a chance that this might involve accumulating snow north of I40 in the eastern Valley.  Any amount of snow is a bonus on Christmas!   After last winter, tracking a potential winter event this year is pretty awesome.  Either way, cold air will quickly spread into the region on Thursday night.  My "lean" is that this could strengthen over time as models now seem to have the synoptics of the storm within their grasp.  Lots of speculation in that last sentence, so take with a huge grain!  As for a second wave which accentuates the snow on the back side, big question mark.  If it does not feed into the front, it likely could keep snow in the air on Christmas days with intermittent snow showers.  The next 24 hours of modeling will likely tell us if this storm will be a nuisance or something bigger.  If anyone is traveling through the Appalachian Mountains on Christmas Eve(specifically I--26, I-40, or I-81), they need to stay up-to-date regarding local weather forecasts.  

 

[Carvers Gap]

MRX with an excellent write-up...

The most uncertain part of the extended forecast will be the
potential for snow across portions of the forecast area. Again as
noted previously, there remains large disagreement with regards to
how quick the cold front moves through the area, and how quickly the
cold air is able to move into the region. The more progressive GFS
suggests most of the precipitation will be out of the area by
Thursday morning with snow showers from northwest flow aloft into
Thursday night. The ECMWF and CMC are slower with a frontal passage
late Thursday, but have trended a bit quicker than previous runs.
Previous runs of the ECMWF depicted wrap around moisture and
precipitation but the 12Z runs have backed off on this solution, and
are in good agreement with the 12Z CMC. Climatologically speaking,
such a deep trough should promote surface cyclogenesis somewhere
across the southeast or mid Atlantic during this time. The 20.00 and
20.12 suite of guidance is suggestive of this solution but again
there remains a lot of uncertainty regarding where this low sets up
and how strong the low will be. All of this will play an integral
role in how much moisture will be left over for potential wintry
precipitation. The official forecast as of this afternoon suggests
temperatures will fall behind the front late Thursday and into
Thursday night. Rain will change over to snow from west to east late
Thursday with light snow showers or flurries lingering across
northern portions of the forecast area through Friday. It is still
too early to forecast snow amounts with any amount of certainty.

What is more certain is that temperatures will plummet behind the
front with deep troughing expected. Temperatures as much as 10-20
degrees below average is a good probability at this point. An
increasing pressure gradient immediately behind the front will create
gusty gradient winds across most of the area. These winds will
obviously bring cold wind chills to the area Friday morning and
Saturday morning. Surface high pressure settles into the region
Saturday and into Sunday with building heights as a ridge builds
into the plains. Temperatures will begin to slightly moderate with
this building ridge but will continue to be below climatology.

 

[TellicoWx]

1 hour ago, Carvers Gap said:

MRX with an excellent write-up...

The most uncertain part of the extended forecast will be the
potential for snow across portions of the forecast area. Again as
noted previously, there remains large disagreement with regards to
how quick the cold front moves through the area, and how quickly the
cold air is able to move into the region. The more progressive GFS
suggests most of the precipitation will be out of the area by
Thursday morning with snow showers from northwest flow aloft into
Thursday night. The ECMWF and CMC are slower with a frontal passage
late Thursday, but have trended a bit quicker than previous runs.
Previous runs of the ECMWF depicted wrap around moisture and
precipitation but the 12Z runs have backed off on this solution, and
are in good agreement with the 12Z CMC. Climatologically speaking,
such a deep trough should promote surface cyclogenesis somewhere
across the southeast or mid Atlantic during this time. The 20.00 and
20.12 suite of guidance is suggestive of this solution but again
there remains a lot of uncertainty regarding where this low sets up
and how strong the low will be. All of this will play an integral
role in how much moisture will be left over for potential wintry
precipitation. The official forecast as of this afternoon suggests
temperatures will fall behind the front late Thursday and into
Thursday night. Rain will change over to snow from west to east late
Thursday with light snow showers or flurries lingering across
northern portions of the forecast area through Friday. It is still
too early to forecast snow amounts with any amount of certainty.

What is more certain is that temperatures will plummet behind the
front with deep troughing expected. Temperatures as much as 10-20
degrees below average is a good probability at this point. An
increasing pressure gradient immediately behind the front will create
gusty gradient winds across most of the area. These winds will
obviously bring cold wind chills to the area Friday morning and
Saturday morning. Surface high pressure settles into the region
Saturday and into Sunday with building heights as a ridge builds
into the plains. Temperatures will begin to slightly moderate with
this building ridge but will continue to be below climatology.

 

Excellent write-up...the development of the Lee low will be on again/off again at this range (hard enough for models to get it right at close range). If you want a "surprise" snow (whether it's in the Rockies/Appalachians/Alps)...this is the setup. It was why the studies have been conducted so much in the Alps (unfortunately our mtns don't go that high, which is why it's more rare here)..due to LP forming in the Lee of the range even when zero vort maxes was depicted in modeling. 

[McMinnWx]

The 18Z GFS ain’t backing down. 

[TellicoWx]

Decent amount of GEFS members still picking up the Lee low and hammering the eastern valley

[Wurbus]

Pretty good snow mean on the GEFS.

[Carvers Gap]

Today's GEFS extended 35 day snow totals below.  Also, take a look at the 18z CFSv2.  It(CFSv2) bounces around quite a bit, but nice run for January.  Anyway, the GEFS extended has snow all of the way to the Gulf Coast.  I think that means a trace(or more) of snow would fall in all of the lower 48 by late January.  If the advertised pattern verifies, there is a chance this has some merit.  Huge grain of salt though as always at this range!  Also, I do like this as it gives a good idea of where the storm tracks might be.....

 

[weathertree4u]

5 hours ago, Carvers Gap said:

Today's GEFS extended 35 day snow totals below.  Also, take a look at the 18z CFSv2.  It(CFSv2) bounces around quite a bit, but nice run for January.  Anyway, the GEFS extended has snow all of the way to the Gulf Coast.  I think that means a trace(or more) of snow would fall in all of the lower 48 by late January.  If the advertised pattern verifies, there is a chance this has some merit.  Huge grain of salt though as always at this range!  Also, I do like this as it gives a good idea of where the storm tracks might be.....

 

The CFS that just ran was insanely cold and snowy for the entire state but especially so from Middle to East TN; I like winter but that run would not be good for the area. 

[Carvers Gap]

Found this to be a really interesting Tweet(saw this in the MA forum)...

 

[Carvers Gap]

Will be very interesting to see the Euro Weeklies tonight at the EPS is out on a limb with its 0z look after d14.  It could score the coup, but not a lot of support for that look right now from other global models.  My guess is there is more of a trough in the East.  There is one tucked under a monster NAO, but the EPS is trying to connect a ridge into the eastern lower 48.  That "could" happen but seems unlikely.  It and the GEFS will have to be watched for a GOA low.  If you watch the 0z EPS side-by-side, you can see it correct eastward with a system just prior to 330.  Now, since we know that is a bias...it can still be used and lines up nicely when that "golf handicap" is applied.  That said, I think this bias in the LR is going to cause problems on the Weeklies as the are derived from the 0z run.  All of that said, the EPS is a great example of how the NAO is muting a very bad Pacific set-up.  If we could get the Pac on board, we would likely see a memorable pattern if the NAO were to hold.  The 0z GEPS is quite close to that...GEFS is a nice compromise between the GEPS and EPS.

[Holston_River_Rambler]

One of the blockier patterns I've seen showing up at the  end of the Euro OP:

 

not sure if it would get the job done for us, in that specific set up, but cool to see the blocking. 

[tnweathernut]

42 minutes ago, Holston_River_Rambler said:

One of the blockier patterns I've seen showing up at the  end of the Euro OP:

not sure if it would get the job done for us, in that specific set up, but cool to see the blocking. 

This pattern would almost certainly put us in the game and we'd likely be tracking something, maybe even multiple events.  The big question is, can we trust an 8-10 day deterministic model run.........  I won't feel good about where we are headed until I'm staring at features like this at 500mb 4-5 days out.  

[Carvers Gap]

The Euro Weeklies control.....

 

[Carvers Gap]

Not to be used as a serious weather map, but the Euro Weeklies Control run says Merry Christmas to the entire freakin' forum.

[Carvers Gap]

In all seriousness, the pattern that is being depicted on LR models and Weeklies runs(CFSv2 and Euro) has one of the most impressive NAO setups that I can remember.  Pacific is TBD.  That said, looks like we are going to see some storms take the low road.  If that verifies, January would have some opportunities I think.  Trying to temper my excitement.  After last winter, anything looks better.  But honestly, the overall pattern looks old school good at times.

[TellicoWx]

5 minutes ago, Carvers Gap said:

In all seriousness, the pattern that is being depicted on LR models and Weeklies runs(CFSv2 and Euro) has one of the most impressive NAO setups that I can remember.  Pacific is TBD.  That said, looks like we are going to see some storms take the low road.  If that verifies, January would have some opportunities I think.  Trying to temper my excitement.  After last winter, anything looks better.  But honestly, the overall pattern looks old school good at times.

Agree, that's showing a prevelant low road track and in best timing for climo...If Pacific cooperates just a little could be a memorable Jan

[Carvers Gap]

4 minutes ago, TellicoWx said:

Agree, that's showing a prevelant low road track and in best timing for climo...If Pacific cooperates just a little could be a memorable Jan

What is interesting about the control run, that is multiple storms which bring that about.

[Daniel Boone]

42 minutes ago, Carvers Gap said:

In all seriousness, the pattern that is being depicted on LR models and Weeklies runs(CFSv2 and Euro) has one of the most impressive NAO setups that I can remember.  Pacific is TBD.  That said, looks like we are going to see some storms take the low road.  If that verifies, January would have some opportunities I think.  Trying to temper my excitement.  After last winter, anything looks better.  But honestly, the overall pattern looks old school good at times.

Like your old school comment buddy. Winters of Yore ! 

      When you're an Antique like me and have been in the weather business as long as I have, you definitely know about "old School".

[BNAwx]

3 hours ago, Carvers Gap said:

Not to be used as a serious weather map, but the Euro Weeklies Control run says Merry Christmas to the entire freakin' forum.

[John1122]

It's epic cold in Russia. If we get the slightest cooperation from the Pacific and gun cross polar flow between that -NAO and a +PNA we'd all need the vodka too. 

[Holston_River_Rambler]

Long range Euro pops a Miller B, this time with a little ore cold air. Different models have been looking at that time frame for a while. Will be interesting to see if that is a legit storm window. 

Verbatim, some of you middle and west TN would like it, some, schmaybe not. 

 

 

 

[Carvers Gap]

5 hours ago, Holston_River_Rambler said:

Long range Euro pops a Miller B, this time with a little ore cold air. Different models have been looking at that time frame for a while. Will be interesting to see if that is a legit storm window. 

Verbatim, some of you middle and west TN would like it, some, schmaybe not. 

 

 

 

That is a nasty looking storm on the Euro after 200.  

[Carvers Gap]

LR after the New Year is full of uncertainty.  MJO is showing some signs of heading to low amplitude warm phases or COD areas of the warm phases.  Will the -NAO connect into a ridge over the EC?  Will a western ridge form and couple with the NAO, and thus create a very wintry pattern?  What about the SSW?  I am less and less of an SSW person.  We had a great one during a spring a few years back.  However, we had a super pattern upended by one since then.  As I watch modeling become more uncertain in the LR(even more so than it has been), makes me wonder if the SSW is wrecking havoc.  One constant on nearly all modeling is a very persistent NAO.  I think that feature has probably saved us from a torch after the first week of December when we lost the PNA.  Would be awesome to see the PNA and NAO both in favorable phases.  We may have a chance of that briefly at times.

So what do I "think" about January.  I think the NAO is going to be there through at least mid-month.  I think there are times that block will be so expansive that it will connect with the eastern ridge.  I think there will be times when it retracts and forces most storms underneath like we are seeing now.  I think there are times when we will see brief windows of a western and/or east Pacific ridge coupled with that NAO.  Right now the cold source region for air is going be much above normal re temps with the exception of Alaska.  It is entirely possible that we see a pattern where Alaska is cold and areas of BN heights stretch SE into the lower 48(northern Plains into the Mid-West).  I am not as encourage by that pattern as I was a few days ago.  I think a potential SSW is going to make, and is currently making, any LR modeling solution extremely suspicious right now.  Let's just hope it doesn't take a favorable pattern and squash it.  OTH, if it is possible the SSW could funnel cold into NA, add in the NAO..and it could get interesting.  

About the only things that I have marginal confidence about are the NAO being a constant, a persistent southern storm track in conjunction with an equal or greater number of cutters, poor cold air sources, and the MJO working back into the COD areas(at least) of the warm phases - not all of those at the same time.  Right now it is like a great pattern is competing with a really lousy pattern....some of each will likely show.   I lean AN for temps in January with normal snowfall.   The great looking pattern from a week ago seems far less certain today.  I do think a western trough is in play now for January.

[Carvers Gap]

The 6z CFSv2 for this date is much colder than other modeling for January, but its MJO is also much different(and maybe wrong?) as it is an outlier.  But it certainly shows how to have a cold-ish pattern.