January 7 - 8 ULL potential

[tnweathernut]

4 minutes ago, Daniel Boone said:

Riding the Rap...maybe my possible big dog bold prediction trigger will be pulled shortly, lol

Just don't start the sentence by telling everyone you know MathMet says a foot is coming....  

[tnweathernut]

1 minute ago, John1122 said:

This one will either end power for some or go down as a moderate to large bust. Maybe even both. That is the nature of ULL snows and their path will likely not be correctly modeled even going off short term now cast models like the HRRR and RAP for more than a few hours in advance. In this scenario bet on elevations but expect your bet to possibly bust wildly even in valley floors.

My thoughts exactly..............

[Icy Hot]

National Weather Service MRX is still not impressed. Only saying 50% of snow for KTRI.

[PowellVolz]

National Weather Service MRX is still not impressed. Only saying 50% of snow for KTRI.

They were never impressed with Dec 24th until Knoxville had 4-6” on the ground


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[Vol Man]

This just popped up on my AccuWeather app....for Kingsport

[Olhausen]

5 hours ago, Holston_River_Rambler said:

6z Euro:

 

Middle Tennessee  is getting the shaft so far this winter. All the good snow has been east and that trend looks to continue.

EDIT: for the Nashville north area anyways.

[fountainguy97]

9 minutes ago, John1122 said:

This one will either end power for some or go down as a moderate to large bust. Maybe even both. That is the nature of ULL snows and their path will likely not be correctly modeled even going off short term now cast models like the HRRR and RAP for more than a few hours in advance. In this scenario bet on elevations but expect your bet to possibly bust wildly even in valley floors.

ULL driven events like this are the absolute worst type of winter event. haha this thing will be "trending" one way or the other up to the last minute most likely.

 

I have to say I'm pretty optimistic with 12km nam, RGEM, RAP and the 3km all showing enhacned banding features. just a matter of where they end up.  Its possible a band of 2" hr rates swings through most of NE TN. and wherever it pivots could get slammed. 

[PowellVolz]

ULL driven events like this are the absolute worst type of winter event. haha this thing will be "trending" one way or the other up to the last minute most likely.
 
I have to say I'm pretty optimistic with 12km nam, RGEM, RAP and the 3km all showing enhacned banding features. just a matter of where they end up.  Its possible a band of 2" hr rates swings through most of NE TN. and wherever it pivots could get slammed. 

I’ve always felt like ULL usually over perform because the mods don’t handle dynamic cooling well. Then again sometimes they can wrap up dry air and destroy itself.


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[fountainguy97]

10 minutes ago, PowellVolz said:

I’ve always felt like ULL usually over perform because the mods don’t handle dynamic cooling well. Then again sometimes they can wrap up dry air and destroy itself.


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i feel like you are right. Mostly because globals often struggle with the mesoscale nature of convection.  And that explains why the GFS family struggles and the EURO does a tad better.  EURO imo has always been the better ULL model.  And speaking of. 12z euro is also starting to pick up an enhanced band of convection. although not as expansive north as high res models. Nice to see EURO still delivering significant snowfall to the Eastern areas and backing up the high res amounts.

This to me validates those beefier high res runs of the RAP and 12km NAM.

[Holston_River_Rambler]

28 minutes ago, Olhausen said:

Middle Tennessee  is getting the shaft so far this winter.

Seems like y'all always get missed. Y'all deserve a Miller B that hammers you and warm noses us. (I hate Miller Bs, lol). 

[Holston_River_Rambler]

Speaking of my own backyard (and probably screwing myself in the bargain), I am just SW of the 3000' Frozen Head mts and have noticed here that we can sometimes squeeze out some extra precip if it is coming in from the SSW (up the valley and then up the plateau, and then up the higher mts). Some of the hi res models have been showing something that looks like that. Not sure if it is some synoptic/ mesoscale feature or the terrain though, in terms of what the models are showing. 

[Daniel Boone]

31 minutes ago, fountainguy97 said:

i feel like you are right. Mostly because globals often struggle with the mesoscale nature of convection.  And that explains why the GFS family struggles and the EURO does a tad better.  EURO imo has always been the better ULL model.  And speaking of. 12z euro is also starting to pick up an enhanced band of convection. although not as expansive north as high res models. Nice to see EURO still delivering significant snowfall to the Eastern areas and backing up the high res amounts.

This to me validates those beefier high res runs of the RAP and 12km NAM.

Trended SE from 06z. Hopefully, not an actual trend . Euro did similar with Christmas Storm at this range. Hopefully,  same deal here. Short range main watch party from here in anyway.

[PowellVolz]

i feel like you are right. Mostly because globals often struggle with the mesoscale nature of convection.  And that explains why the GFS family struggles and the EURO does a tad better.  EURO imo has always been the better ULL model.  And speaking of. 12z euro is also starting to pick up an enhanced band of convection. although not as expansive north as high res models. Nice to see EURO still delivering significant snowfall to the Eastern areas and backing up the high res amounts.
This to me validates those beefier high res runs of the RAP and 12km NAM.

Doesn’t the Euro have issues with cutting off the precip shield to quick on the NW side at times?


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[fountainguy97]

2 minutes ago, PowellVolz said:

Doesn’t the Euro have issues with cutting off the precip shield to quick on the NW side at times?


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Almost always. Yes. Most globals have convective feedback issues which can stunt precip growth away from the center of a storm system. 
 

Iike @Daniel Boone said it’s time for high res models to take the lead. But I find it encouraging to see euro coming in beefy for the mountains. 

[Holston_River_Rambler]

SREF H5 mean looks more...energetic...with the energy. 

[tnweathernut]

Seems like the afternoon AFD from the NWS in Morristown is late today.  Maybe they are wanting to look at 18z before issuing?  I thought they normally had something out by 2:30 EST?  At the very least I think a special weather statement is warranted.  Going to be interesting to see how they handle.

[jaxjagman]

[John1122]

1 minute ago, tnweathernut said:

Seems like the afternoon AFD from the NWS in Morristown is late today.  Maybe they are wanting to look at 18z before issuing?  I thought they normally had something out by 2:30 EST?  At the very least I think a special weather statement is warranted.  Going to be interesting to see how they handle.

It's normally 3:15-4:15ish. 

[fountainguy97]

this 12km run lol 9 inches of snow in 6 hrs in southern Unicoi

[John1122]

Looks like we got NAM'd just a little bit. 

[John1122]

Middle and West Tennessee posters after the NAM.  

[John1122]

1 minute ago, Holston_River_Rambler said:

But is the NAM a conjuror of cheap tricks? 

Most assuredly. 

[Holston_River_Rambler]

1 minute ago, John1122 said:

Middle and West Tennessee posters after the NAM.  

But is the NAM a conjuror of cheap tricks

[John1122]

Just now, Holston_River_Rambler said:

But is the NAM a conjuror of cheap tricks

It's magic is tricking the board!

[Holston_River_Rambler]

Good we have a theme for this one now..

[PowellVolz]

this 12km run lol 9 inches of snow in 6 hrs in southern Unicoi

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[Olhausen]

42 minutes ago, jaxjagman said:

Looks like they added more snow to the west when compared to the morning update. If the nam was even close to correct this winter I’d be counting snow in feet by now. Reality has been just under an inch of snow for the season though.

[Icy Hot]

Winter Storm Watches now posted for NE TN and WNC border counties.

[tnweathernut]

Excellent discussion by the Morristown peeps:

AREA FORECAST DISCUSSION
National Weather Service Morristown TN
348 PM EST Wed Jan 6 2021

LONG TERM...(Thursday night through Wednesday)...

The main story for the long term period is the chance for
widespread snowfall Thursday night into Friday, with several
inches expected in the east TN mountains and a chance for some
accumulating snow down into the valley floor. Will be focusing the
discussion on this system as a result.

Thursday evening a deep southern stream upper trough will cutoff
over the Arklatex region, shifting east across northern
Mississippi and Alabama through the night and into the Carolinas
on Friday. There remains some disagreement with the placement of
the upper low as it traverses the TN/MS/AL border Thursday night,
which has implications on precip type and amounts. This lends
itself to a still-low confidence forecast for the lower elevations
of the TN valley. Elsewhere, especially in the east TN mountains
along the NC border, confidence is much higher in precip type and
reasonably high with regards to amounts.

Precip looks to spread into the southern counties during the
evening hours tomorrow, working north through the central valley
by midnight or so, and finally up into the northern zones by
daybreak Friday morning. This seems to be pretty well agreed on in
the numerical guidance. BUFR soundings from various models do not
support any snow reaching the lower elevations until after
midnight, but between evaporative and dynamic cooling and the
baseline thermal profile, expect that at minimum a rain/snow mix
will be seen fairly early on at elevations above 2,000 ft or so.
Snow levels will work their way lower through the night though,
and expect to see a rain/snow mix down to the valley floor during
during the very early morning hours on Friday. Let me go ahead and
address the elephant in the room here and say that it doesn`t
appear that this will be a very impactful snow event for the TN
valley south of roughly Morristown or maybe even a little further
north than that. Looking upstream, there is no source of frigid,
dry arctic air that will surge south into the TN valley to support
prolonged periods of snow at low elevations. Model soundings show
a weak warm nose induced by southeasterly flow across the
mountains, or perhaps a deep isothermal layer near the freezing
line, through the time period where snow will exist. Given
forecast surface temperatures, the driving factor in any
accumulating snow will be precip rates and frankly they don`t look
outstanding outside of the Appalachians where orographic lift
will help enhance rates there. Have a tenth or two of accumulation
from the southern valley up to around the Morristown area in the
forecast.

Now, moving on to the plateau, mountains, and other locales. The
best window of heavier precipitation rates looks to be from roughly
midnight Thu night through daybreak Fri morning. This is when the
best low and mid level frontogenetic forcing transits the area. More
susbtantial deep ascent will stay east of the forecast area into the
Carolinas. Likewise, a persistent TROWAL feature is absent across
our CWA, so this will be a quick hitting system in large part.
Still, given the low freezing levels to start, expect that the
mountains could pick up a quick 4-6" of snow late Thursday night as
this system passes by. Some northwest flow snow showers will likely
linger into Friday evening, but the best accumulating snowfall will
be done by late Fri morning most likely. On the plateau, the same
situation applies. Being further removed from the best forcing,
expect snow amounts in the 1-3" range there.

Having said all of that, decided to hoist up a Winter Storm Watch
for the east TN mountains and far western NC from 8pm EST Thu
through 8pm EST Fri. Confidence seems high enough to warrant that at
this time. If trends continue, will likely need an advisory for the
plateau. However, there`s enough uncertainty there, as well as the
far northern TN valley and southwest Virginia (both of which will be
furthest from the best moisture and lift) to hold off on any
headlines now. Have snowfall accumulations in the 1-3" range in
those locales as well but would not be surprised if those change (up
or down) in future forecast packages.

Otherwise, for the remainder of the long term period, cool and dry
conditions continue through the weekend. There is a chance another
southern stream system could bring chances for widespread wintry
precip again on Monday night into Tuesday, but uncertainty is very
high right now and it not worth going into detail on that system
just yet.

[John1122]

I fully expect somewhere to get 4+ inches of snow without any kind of advisory or warning.