11/28-29 Snow Event

[Cyclonicjunkie]

Nearly all models have come into agreement of closing off an upper level low and retrograding this system into the Ohio Valley/ Great lakes region. There is very good support for this to happen and this is not your everday ULL either...this is being advertised as a very deep and potent upper level low.

There are many smaller scale details to workout such as the exact track of this system and the exact strength of this system. Most models close this low off near the TN valley and move it up towards the great lakes where it just sits and spins for days. In my opinion this is the most likely track for this system and the one that I will use to go into more detail.

IF this scenario plays out there will be snow falling in the TN valley as thickness values crash behind the cold front. Now being that this system gets cutoff from the jetstream it will have nothing to steer it and it will just sit and spin over the great lakes for a few days where it will fetch precip all the way down into Tennessee and maybe even further south. This is a very powerful system and it will likely grab vort maxes from several hundred miles away and rotate them thru the area as it is spinning over the lakes.

Its way to early to be talking about where any accumulation occurs as we still dont know the exact track....models have latched on to the general scenario that I have just told you about but there will likely be several changes as the models get a better handle on this situation and exactly where the snow occurs will become more clear...but there will be a very large area that will be effected by the snow if models are correct.


Alot of model support for a day 7 threat.

12zGFS



The 12zECM is super sexy



12zCMC is much further west but still snows on west TN






OH yeah...I forgot to add the 12z Nogaps which is even more sexy

[Adam]

Toot getting me excited already, I didn't believe I would get any snow last year when a similar event happened. I did though, I had about an inch when all was said and done. I still don't think we see any accumulation outside of the Plateau and the mountains.

[Clarksville Snowman]

Finially winter time model madness begins!! I am ready for some winter with some good tennessee snows hopefully.

[jmundie]

What I don't understand is why this thing isn't colder in the core.

But, I guess most ull's are modeled to warm, hence why they end up being surprise snow producers.

And this one is mammoth. Just plain gigantic.

[Adam]

What I don't understand is why this thing isn't colder in the core.

But, I guess most ull's are modeled to warm, hence why they end up being surprise snow producers.

And this one is mammoth. Just plain gigantic.

Your right which is the only chance of any accumulating snow in Middle Tennessee. Unless it just snows really hard.

[Cyclonicjunkie]

Toot getting me excited already, I didn't believe I would get any snow last year when a similar event happened. I did though, I had about an inch when all was said and done. I still don't think we see any accumulation outside of the Plateau and the mountains.

Adam...this is not an elevation dependant snow threat its a cold core low which makes its own cold air...but like I said earlier its way too early to be talking accumulations. 

[Math/Met]

It is probably too far off to mention this, but this system could be the first real mountain wave threat this fall as well. Of course, there are a lot of details to be worked out, including the low placement, stability of the atmosphere, and the exact wind profile. But, that is something to watch for East Tennessee on the warm side of this low. It could be an entertaining system.

[Eric]

What I don't understand is why this thing isn't colder in the core.

But, I guess most ull's are modeled to warm, hence why they end up being surprise snow producers.

And this one is mammoth. Just plain gigantic.

I'll take a stab at this one....and I could definitely be wrong.  The progged H5 temps feeding into the ULL are only -25C (-13F).  While the air is of cPk origin, it's being modified as it's pulled out of Canada into the ULL.  IIRC, the air temp in Fairbanks earlier this week was -30F...that air is still locked up over the Arctic via the polar jet.

[Adam]

Adam...this is not an elevation dependant snow threat its a cold core low which makes its own cold air...but like I said earlier its way too early to be talking accumulations. 

Yeah but what are the odds of it getting cold enough here. The ground temperature will not even be close, I don't think.

[Cyclonicjunkie]

Yeah but what are the odds of it getting cold enough here. The ground temperature will not even be close, I don't think.

I really didnt want to talk about accumulations this early but if you insist

Im sure you have heard that it dont have to be freezing for snow to accumulate? Strong upper lows are very dynamic and if you get under the right amount of upper level energy...snow will have no problem accumulating. With that said it wouldnt surprise me one bit if temps dropped several degrees below freezing statewide with the monster ULL that is being modeled. I dont think people realize how powerful the storm is thats being modeled ....some of the models in the past have closed this thing off with FIVE closed contours. That is a beast of a storm and would advect serious amounts of cold air into the region.

Now with all that said... this storm is still a week out and is subject to drastic changes

[Adam]

Since you know what you are talking about, I will leave it at that. I was just saying that it would be hard to accumulate with the warm ground temps.

[jmundie]

I'll take a stab at this one....and I could definitely be wrong.  The progged H5 temps feeding into the ULL are only -25C (-13F).  While the air is of cPk origin, it's being modified as it's pulled out of Canada into the ULL.  IIRC, the air temp in Fairbanks earlier this week was -30F...that air is still locked up over the Arctic via the polar jet.

Yeah - I've been noticing there seems to be  a small disturbance at h5 that seems to be blocking the true cold from dumping out of Alaska. If that gets pulled into this trough, then it seems there would be uninterrupted flow through Alaska down into our mega low... That seems to be the only thing getting in the way of a nov 51 repeat

[Cyclonicjunkie]

Since you know what you are talking about, I will leave it at that. I was just saying that it would be hard to accumulate with the warm ground temps.

Lol...I was just saying that this will not be limited to the higher elevations if it happens...but yes snows that occur with warm ground temps tend to take longer to overcome the melting process at the surface. But with a dynamic system such as the one being modeled.... snow rates are usually rather high and warm ground temps cant hold off the rate of snow that is falling and then the snow that has fell creates a cold layer on the ground and wa-la you now have a conducive surface for snow to accumulate on.

In no way am I saying that you are going to get accumulating snow with this system

[tennessee storm09]

another thing thats very impressive will be the sustain winds along with gusts... isobars look very tight.

[Math/Met]

another thing thats very impressive will be the sustain winds along with gusts... isobars look very tight.

Yes, the GFS really starts to crank up the LLJ over Tennessee in response to the pressure gradient between the strong low and the high pressure off the East Coast. This along with several other factors is why I think this could be a mountain wave wind event over the mountains and foothills of East Tennessee. A lot could change in the next few model runs, but it has that look at the moment.