January Medium-Long Range Discussion

[Carvers Gap]

It is important to take the snow off the ground from the two systems this week(tonight and Friday).  Once one does that, most of the eastern valley is blanked by the 18z GFS.  TRI has been blanked for the past two runs.  The previous snow on the ground makes those runs look better than they actually are.  The anafront dies after it comes across the Plateau.  For TRI, right now we are chasing a cold front and not snow.

[BNAwx]

5 minutes ago, Matthew70 said:

I will take 3-6” anytime any day in the winter. So many not happy it’s not showing a foot.  Not here just other places.   That amount with the temps will be bad enough.  It won’t melt.  If we get a lot more then it will cripple the area with the temps coming behind it. 

There’s a reason Nashville has rarely witnessed a 12”+ snowfall.  Too far west to get prime snowfall from a Miller A out of the gulf and no elevation to enhance lift.  There’s more reasons I’m sure.  We’re more likely to get to that total from a well placed upper level low.

[Carvers Gap]

For western and middle forum areas it is 4-5 inches of snow near the MS River and 2-3" of snow to the Plateau w/ diminishing amounts as one goes eastward.  There is a lollipop over TYS, but the rest of the eastern Valley gets 0.5-2".  Kuchera is probably a bit more.  But that run was rough compared to where it was a couple of days ago.  

Very close to tracking just a brief, intense snow band for the eastern 1/3.  Hopefully we see it look a bit better during the next couple of days....but the system is trending w/ less precip w/ each passing run.

[PowellVolz]

Didn't see this, but pretty much what I was wondering as well. 

Not something we deal with much. I know the Christmas 2020 system was highly localized. I had around 6” in Halls but 10 min west of me in Powell had 2”. A friend in deep W Knoxville had almost 6”. My in laws in Union County, about 15 min away had an inch or so.


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[Silas Lang]

2 minutes ago, PowellVolz said:

Not something we deal with much. I know the Christmas 2020 system was highly localized. I had around 6” in Halls but 10 min west of me in Powell had 2”. A friend in deep W Knoxville had almost 6”. My in laws in Union County, about 15 min away had an inch or so.


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Yeah,my folks in Anderson County had about 1.5 inches. We stayed over for Christmas and driving back it was weird seeing it get snowier as we went east. Pretty tight gradient. I had about 5 inches in Fountain City. 

[PowellVolz]

For western and middle forum areas it is 4-5 inches of snow near the MS River and 2-3" of snow to the Plateau w/ diminishing amounts as one goes eastward.  There is a lollipop over TYS, but the rest of the eastern Valley gets 0.5-2".  Kuchera is probably a bit more.  But that run was rough compared to where it was a couple of days ago.  
Very close to tracking just a brief, intense snow band for the eastern 1/3.  Hopefully we see it look a bit better during the next couple of days....but the system is trending w/ less precip w/ each passing run.

GFS Kuchera….hope it is ok to show




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[Carvers Gap]

1 minute ago, PowellVolz said:

GFS Kuchera….hope it is ok to show




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Is that for the storm only?  The problem I am seeing w/ some of the maps is they include 1-2" of total snow from tonight and Friday.  I have the map for the storm, and it isn't close to that.

[Carvers Gap]

Here are the Kuchera and 10:1 maps:

 

[ShawnEastTN]

Here is kuchera Sunday before the storm.

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[ShawnEastTN]

Makes me question the calculations between Weatherbell and Pivotal weather as they don't seem to line up.

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[Carvers Gap]

10 minutes ago, ShawnEastTN said:

Makes me question the calculations between Weatherbell and Pivotal weather as they don't seem to line up.

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I can say this, the amount of 24 hour precip has dropped since yesterday.  If we can get 0.35"(18z GFS) of water to fall into very cold air, we could reach Pivotal's algorithm fairly easily and surpass it.  But the main message on modeling since 12z is that the front dies as is comes of the Plateau.  That said.  It is just Tuesday, and the details are 100% going to change over the next 5-6 days.  

And also, we are in the 5-7 day window where models are notorious for losing storms.  Let's see where this is by say Thursday.  Since the maps are posted here, we can see if modeling ups totals.  

[Carvers Gap]

11 minutes ago, ShawnEastTN said:

Makes me question the calculations between Weatherbell and Pivotal weather as they don't seem to line up.

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I have found WxBell algorithms to be decent.  Pivotal is almost always overdone for MBY.  

[ShawnEastTN]

Agree, though I also think it appears to be moving through faster on 18z compared to previous runs. CAA seems to blast further south quicker.

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[Stovepipe]

The buffkit meteograms show a bump at 18z from 12z for both TYS and TRI, 11:1 and Cobb.  Not by much, but notable.

[ShawnEastTN]

I really wouldn't be surprised if in future runs it pops a low in the Gulf that hopefully will be a good tracking storm. Fingers crossed it does.

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[John1122]

This is just from the Sun/Monday system. 

 

Edit nvm. Posted wrong image 

 

[Carvers Gap]

20 minutes ago, ShawnEastTN said:

Agree, though I also think it appears to be moving through faster on 18z compared to previous runs. CAA seems to blast further south quicker.

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Generally, east -> west storms moving quickly will blank TRI from I-81 westward if they are just light snow events.  Knoxville sometimes works around the rain shadow there(see the graphs Stove just posted).  I have noticed west and north Knoxville will often get more than MBY if precip amounts are equal and the trajectory is east -> west (temps about the same comparatively).  December 20' is what we need to work towards if this is going to be an anafront.  Just need the front to come roaring across the state, and roll the dice.  For now, it very much looks like this loses steam as hit crosses the Plateau with the exception of the lollipop over TYS which may or may not be legit.   But again, we are in this window where modeling just struggles.  I don't know if we lose data on the vortex over the Pacific or if it just gets sampled better as it approaches the US coast.  

[John1122]

This is the total from just the Sunday/Monday event. 

 

[TellicoWx]

1 hour ago, PowellVolz said:

In a anafrontal system, is their elements that can enhance qpf that the mods don’t pickup on? NW flow, steep lapse rates, low level moisture, etc….? I’m assuming it could be rationed higher from cold 850’s?


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In an anafrontal setup some things that models will not have a grasp of at this ramge:

1) the depth of the shallow low level moisture. This range they have a tendency to sometimes dry the DGZ out to quickly, not picking up on where the moisture banks up against micro climate areas (such as the plateau/foothills etc).

2) Under estimate how far ahead the shallow arctic air has actually advanced during very powerful cold fronts.

3) The exact placement of Vertical Velocities. Becomes more important with anafrontal due to having to rely on the UVVs more for the lift, than have the traditional SLP aided lift.

[Carvers Gap]

12 minutes ago, John1122 said:

This is the total from just the Sunday/Monday event. 

 

That fits what I am seeing(for this run).  

[Carvers Gap]

I would say if this is there at 0z, start a thread.  I would be super surprised if some in the forum don't see some decent snow from this.  I have been holding off on hitting any LR stuff today so as not to slow the roll of this great storm discussion.  The Euro ext tonight looked exceptional.

[Carvers Gap]

The Euro (ext) basically has a decent window from Jan 28 through all of February.  A quick ridge rolls through from the 23rd to the 27th, and then a trough sets up over the SE very abruptly around the 28th.  Great look.  Nice PNA ridge forms out West w/ undercutting, and trough centered just to the southwest of the Aleutians.  The 28th fits the MJO rotation almost perfectly as it should reach phase 7 by late month or early Jan.  Then I agree w/ Cosgrove, March goes warm...but I could see it start cold.  The SSW is maybe decent today?  That would bring cold 2-3 weeks from today.

[Uncle Nasty]

Essentially only down around Chattanooga is it around an inch. Though I don't fully understand considering it depicted snow the entire time, so must be accounting on some mixing to occur there. Chattanooga aside it's roughly the same 3-4" with some spots going 5-6".

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If it actually pans out like this run, it won't even be laughable anymore. Chattanooga is in a little snow dome with a dusting and the entire state getting 2"-5"+. I guess if it does happen, all we can do down here is shrug our shoulders and carry on!

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[Vol4Life]

So has the storm sped up?  Last night we were looking at Mon/Tues.  Are we now looking Sun/Mon?

[PowellVolz]

Is that for the storm only?  The problem I am seeing w/ some of the maps is they include 1-2" of total snow from tonight and Friday.  I have the map for the storm, and it isn't close to that.

No it’s not but it did not look like there’s any accumulation worth noting before the Monday system, especially in the lower elevations.


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[Carvers Gap]

Evening disco from MRX and pretty decent discussion for a system still 5-6 days out.

Sunday is dry but then all eyes turn toward our system for next
week. It`s still too early to go into much detail in regards to
snowfall amounts as timing and QPF amounts will play a large role in
accumulations. With that said, NBM probabilistic guidance is showing
roughly a 40 to 50% chance of seeing 1" of snowfall along and north
of I-40 with a 50 to 60% across southwest VA. Probabilities are lower
across the southern TN Valley at 20 to 30%. The probability for 2"
of snowfall or greater along I-40 and north drops down to a 30 to a
30 to 40% chance. While snowfall amounts are TBD there is high
confidence in much colder temperatures in place Monday into Tuesday.
The new day 7, which is Tuesday, currently has high temps in the mid
to upper 20s with overnight lows in the single digits across the
forecast area. These values are around 20 degrees below normal.

[Carvers Gap]

Winter Wx Advisory has been posted for the TN side of the Apps(higher elevations only).

[Matthew70]

Channel 4 here has scaled way back.  Some are now saying hardly any snow.  Hilarious how the pendulum swings.  If no snow I do hope this cold spell is very short lived.  I will cover my new landscaping hoping to save it.  Cold & dry can get lost for all I care.  Working in it sucks. 

[Greyhound]

Channel 4 here has scaled way back.  Some are now saying hardly any snow.  Hilarious how the pendulum swings.  If no snow I do hope this cold spell is very short lived.  I will cover my new landscaping hoping to save it.  Cold & dry can get lost for all I care.  Working in it sucks. 

Wonder how that crow tastes since they are the ones that put out that snowmageddon info yesterday?

[Matthew70]

1 minute ago, Greyhound said:

Wonder how that crow tastes since they are the ones that put out that snowmageddon info yesterday?

I’d rather them not call for it.  Thats when we usually get more snow.