January Medium-Long Range Discussion

[Carvers Gap]

1 hour ago, fountainguy97 said:

For people East of the Plateau you want the EURO to keep trended for a negative tilt.  The only way we score is if we get a low to form and fire convection. If not then yes. The moisture will go poof.
 

the good news is the gfs is ticking that way but still not enough. That's the only way this brings much of anything to Eastern areas.

 

Need this to continue. We don't need an 1" of precip with this. Its so cold just need a few hours of good rates.

Models still bouncing around all over the place.  I swore years ago never to track a storm from seven+ days out.  Now, I remember why.  Not again after this one.  LOL.  Yeah, east -> west trajectories are not how we score in most of the eastern valley.  There has to be a component where the system backs(slp forms to our east) and preferably a component where moisture comes from the southeast or even southwest(even w/ the risk of a warm nose).  Really, I don't think clown maps are going to matter with this one.  What is going to matter is how much moisture is on the qpf map for each area.  What I will be watching is how much moisture is going to be available.  If areas get 0.2 - 0.3 (water equivalent), that "could" be really good if the precip line is far enough behind the front.  If the precip arrives with the front, totals will be much lower.  So things to watch for me are where the precip is in relation to the front and overall precip amounts for the event. Even at TRI where this has been a strong "no go" for days, if we get 0.1" of water...that could be a couple of inches of snow.  For now, I still think the eastern valley is going to need a lot of help as you note.  I think a general 1-2" of snow is in play for most eastern areas.  To get above that, we are going to need something similar to what you have shown.

FWIW, the 6z GEFS trended way down on storm totals, but it is still bouncing around.  

[Carvers Gap]

From MRX this morning:

Early next week VERY cold temperatures will dive out of Canada
towards the southeast US. This will definitely bring with it
bitterly cold temperatures dropping into the teens an single digits
on Tuesday and Wednesday morning. And in addition accumulating
snowfall in the valley cannot be ruled out. This snowfall
possibility is still 5+ days out so the models/forecast can AND WILL
change over the next few days, and focusing in on a single
deterministic model run this far out is unwise. Probabilistic
guidance continues to show the possibility of seeing an inch of snow
Monday/Tuesday at around 50% along and north of Interstate 40,
dropping down to around 25% chance near the TN/GA border. The
probability to see 3 inches of snow drops down to around 20% along
Interstate 40. Many people will focus on the snow potential early
next week, but there is MUCH higher confidence on the bitterly cold
temperatures the first half of the week. With winds expected to see
an uptick at times we could see single digit wind chill values at
Chattanooga Tuesday morning, and even sub zero wind chill values on
the plateau at this time.

[fountainguy97]

1 hour ago, Carvers Gap said:

Models still bouncing around all over the place.  I swore years ago never to track a storm from seven+ days out.  Now, I remember why.  Not again after this one.  LOL.  Yeah, east -> west trajectories are not how we score in most of the eastern valley.  There has to be a component where the system backs(slp forms to our east) and preferably a component where moisture comes from the southeast or even southwest(even w/ the risk of a warm nose).  Really, I don't think clown maps are going to matter with this one.  What is going to matter is how much moisture is on the qpf map for each area.  What I will be watching is how much moisture is going to be available.  If areas get 0.2 - 0.3 (water equivalent), that "could" be really good if the precip line is far enough behind the front.  If the precip arrives with the front, totals will be much lower.  So things to watch for me are where the precip is in relation to the front and overall precip amounts for the event. Even at TRI where this has been a strong "no go" for days, if we get 0.1" of water...that could be a couple of inches of snow.  For now, I still think the eastern valley is going to need a lot of help as you note.  I think a general 1-2" of snow is in play for most eastern areas.  To get above that, we are going to need something similar to what you have shown.

FWIW, the 6z GEFS trended way down on storm totals, but it is still bouncing around.  

Yeah need that backing into the cold boundary from a developing coastal.  Probably need a thread for 12z. Mid-west TN basically a lock for some frozen

[Carvers Gap]

1 hour ago, fountainguy97 said:

Yeah need that backing into the cold boundary from a developing coastal.  Probably need a thread for 12z. Mid-west TN basically a lock for some frozen

I was reading JB this morning, and he thinks the storm will be flatter.  I have no idea what that means in regards to the outcome of this storm, but there seems to be a school of thought that modeling is adjusting quickly to the block, and this is not dialed-in.  I was looking at Holston's 1988 post in banter, and maybe this is a 1988(light) set-up.  The 6z Euro control pretty much completely lost the entire storm once it left west TN.  LOL.  The 6z mean looks like 0z.  The Euro seems to be transitioning to more of a dying cold front over this forum area, and a developing low from the Panhandle to off the EC.   Not sure if it helps us, but it could bring some semblance of a slug of moisture up the eastern valley if that developed.  Some super sketchy solutions out there right now.  I don't know which to trust.

[Holston_River_Rambler]

That's definitely an interesting look at H5 on the control, and that is after the front has washed out. 

[Silas Lang]

16 minutes ago, Holston_River_Rambler said:

That's definitely an interesting look at H5 on the control, and that is after the front has washed out. 

What does this look imply? Sorry not good at reading these maps. 

[Holston_River_Rambler]

It's the control, so the resolution is lower, but it looks quite a bit slower that the OP for one thing.

Here is the 0z OP for the same time:

The end result might not be any different, but I like the idea of 2 shortwaves interacting near the MS river and Gulf coast:

There's room to amplify and a semi phased shortwave trough to go negative at the right longitude for us.

You can see it trying to do it on the 0z Euro. 

See how as the shortwave (indicated by the blue lines) rolls overhead precip increases pretty quickly over east TN. 

Maybe if it can dig more and slow a bit we get more of a Miller A type solution. 

 

[fountainguy97]

7 minutes ago, Holston_River_Rambler said:

It's the control, so the resolution is lower, but it looks quite a bit slower that the OP for one thing.

Here is the 0z OP for the same time:

The end result might not be any different, but I like the idea of 2 shortwaves interacting near the MS river and Gulf coast:

There's room to amplify and a semi phased shortwave trough to go negative at the right longitude for us.

You can see it trying to do it on the 0z Euro. 

See how as the shortwave (indicated by the blue lines) rolls overhead precip increases pretty quickly over east TN. 

Maybe if it can dig more and slow a bit we get more of a Miller A type solution. 

 

Yes I believe that's a suitable outcome for all of TN. Middle/west gets the frontal aspect and then the lingered shortwaves backfill the front as a low pops for the east. 
 

it's not worth much the but 12z NAM is in line with the euro of a slower and more solidified "backend" shortwave (I guess that's how we will call it)

[snowbird1230]

8 minutes ago, fountainguy97 said:

Yes I believe that's a suitable outcome for all of TN. Middle/west gets the frontal aspect and then the lingered shortwaves backfill the front as a low pops for the east. 
 

it's not worth much the but 12z NAM is in line with the euro of a slower and more solidified "backend" shortwave (I guess that's how we will call it)

Does the NAM go out that far?

[Holston_River_Rambler]

1 minute ago, snowbird1230 said:

Does the NAM go out that far?

This is high stakes territory snowbird, we've reached the land of "extrapolate the NAM" 

[PowellVolz]

It's the control, so the resolution is lower, but it looks quite a bit slower that the OP for one thing.
Here is the 0z OP for the same time:

The end result might not be any different, but I like the idea of 2 shortwaves interacting near the MS river and Gulf coast:

There's room to amplify and a semi phased shortwave trough to go negative at the right longitude for us.
You can see it trying to do it on the 0z Euro. 

See how as the shortwave (indicated by the blue lines) rolls overhead precip increases pretty quickly over east TN. 
Maybe if it can dig more and slow a bit we get more of a Miller A type solution. 
 

How much If any does the tilt matter for a winter storm? I know what it means for severe weather.


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[PowellVolz]

Does the Euro still have issues with hanging energy back?


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[weathertree4u2]

One of our local Nashville mets said this morning, that it would likely be Saturday give or take before they could lock in amounts but that it looked like at this time that chances were good for areas along and north of I-40 to receive accumulating snow Sunday into Monday - all of this, as has been discussed should come into better focus over time. 

[Carvers Gap]

The 12z GFS backed the flow by turning(ever so slightly) the system to the north after first flattening it out.  If that lows trends closer to the coast, more interesting system ensues.  Makes a huge difference for E TN.

[Carvers Gap]

So far...the trend is to flatten the system out a bit as it enters the forum area.  I wasn't sure what JB meant by that but you can see it on the precip panels.  That is allowing for a bit more confluence - I think.

[Carvers Gap]

The CMC probably won't get there this during this run, but it has a SLP in the Panhandle at 126.   This is the trend for sure so far and a new twist.

[Carvers Gap]

at 132, it is weak, but that is a Miller A.

[Carvers Gap]

And if the GFS or CMC trend about 150-200miles northwest (plenty of time for that trend), this is a different ballgame.

[John1122]

The ICON, which was the first to show the solution the Euro had last night, is now a big hitter today at 12z except for the far southern valley of East Tennessee. It actually has temp issues there.

[Carvers Gap]

I think that we are seeing some sort of energy transfer to the coast which is why the front is dying so early now.  Not sure if that helps, but definitely can see it on the CMC. 

[Carvers Gap]

3 minutes ago, John1122 said:

The ICON, which was the first to show the solution the Euro had last night, is now a big hitter today at 12z except for the far southern valley of East Tennessee. It actually has temp issues there.

Yep, sure does/did.  It comes out flatter, and then almost pops what I would call a lee side low which hugs the Apps.  

[fountainguy97]

1 hour ago, Holston_River_Rambler said:

This is high stakes territory snowbird, we've reached the land of "extrapolate the NAM" 

"I swear bro. The NAM has this one nailed. Trust me"

 

someone start the thread. My last one went poof haha

[John1122]

The old extended NAM would have some 30+ inch lolipops for us. DGEXerizating it was called.

[Holston_River_Rambler]

3 minutes ago, fountainguy97 said:

"I swear bro. The NAM has this one nailed. Trust me"

 

someone start the thread. My last one went poof haha

IMO we wait until this next cutter is out of the way. 

[Holston_River_Rambler]

This is such a weird complicated set up I'm going to try to do a bigger post later with all the elements going into this potential. 

[PowellVolz]

That weird lollipop keeps popping up over Knox, Blount and Sevier Co. Kinda weird… it’s not every run but it’s been there about 50% of the time. Could this be some kind of backing or damming with the anafrontal moisture up against the GSM?


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[Carvers Gap]

I used to think those were erroneous lollipops, but Knox Co has to have some sort of micro-confluence there.  Tellico had a great illustration overnight.  On more than one occasion, Knoxville has outperformed areas to the north.  I do think the front gets sheered by the time it gets to TRI as precipitation tries to get over the Apps.  But that alley to the west of Knoxville seems to let a lot of precip in....I see that w/ summer thunderstorms as well.  It seems if one area can dodge the Plateau rain shadow, it is Knoxville.

It is also possible that there is some smoothing from the Smokies which affects that.  We often have way to much digital snow here as modeling will often smooth snow amounts too much.

[John1122]

The UKIE is full western trough/se ridge and we stay warm dry over most of the state. It and the Euro often have similar outcomes as they likely have some common dna. We will see if the Euro is more like it soon. 

[Daniel Boone]

9 minutes ago, PowellVolz said:

That weird lollipop keeps popping up over Knox, Blount and Sevier Co. Kinda weird… it’s not every run but it’s been there about 50% of the time. Could this be some kind of backing or damming with the anafrontal moisture up against the GSM?


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Model's have ingested data from previous similar situations. Could be those occurences produced more in that area, ie., Christmas 2020. That would reflect from the Model's output. 

[PowellVolz]

I used to think those were erroneous lollipops, but Knox Co has to have some sort of micro-confluence there.  Tellico had a great illustration overnight.  On more than one occasion, Knoxville has outperformed areas to the north.  I do think the front gets sheered by the time it gets to TRI as precipitation tries to get over the Apps.  But that alley to the west of Knoxville seems to let a lot of precip in....I see that w/ summer thunderstorms as well.  It seems if one area can dodge the Plateau rain shadow, it is Knoxville.
It is also possible that there is some smoothing from the Smokies which affects that.  We often have way to much digital snow here as modeling will often smooth snow amounts too much.

Our last two decent valley systems, Christmas 2020 and March 2022(?) over performed in a 50 mile radius over Knoxville and both of them had some trailing moisture up the valley that just enhanced over Knox Co but didn’t really funnel north of there. Just sorta dead headed.


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