1/10-1/12 Southern Slider

[Hurricaneguy]

9 minutes ago, tnweathernut said:

More of a microclimate thing, Jax.  Unicoi, Greene & parts of Washington County tend to pull downslopes and dryslots like a magician pulls a rabbit from a hat.  It's a talent we have in spades.

For real! I'm mega scarred from last year's letdown in Greeneville. Everyone celebrating while I'm surrounded by slush. I'm cautiously optimistic for Friday. Honestly dont even know if I can get excited this time until the ground is completely white.  Last time that happened March surprise storm 2022 btw

[ladyjmayo]

2 hours ago, Carvers Gap said:

Give me the 12z Canadian ensemble and let’s roll.

I'll second that!

[Reb]

MRX disco

 

858
FXUS64 KMRX 072021
AFDMRX

Area Forecast Discussion
National Weather Service Morristown TN
321 PM EST Tue Jan 7 2025

...New SHORT TERM, LONG TERM, AVIATION...

.SHORT TERM...
(This evening through Wednesday)
Issued at 320 PM EST Tue Jan 7 2025

Stubborn clouds are slowly eroding across the Valley but may try to
return overnight. Otherwise, cold temperatures will maintain their
grip on the area tonight and Wednesday, with Valley highs again
mainly in the 30s. Expecting any overcast morning clouds to scatter
out around midday.

A mostly zonal pattern aloft will do little to dislodge the cold
surface air, but a weak disturbance may touch off some flurries
Wednesday afternoon and evening across SW VA.

&&

.LONG TERM...
(Wednesday night through next Tuesday)
Issued at 320 PM EST Tue Jan 7 2025

.LONG TERM...

Key Messages:

1. Confidence is strongly trending in favor of a significant winter
storm across the southern Appalachian region, with widespread
accumulating snow possible over the forecast area Friday into
Saturday.

2. Some uncertainties remain though - especially with regards to
amounts. Time will bring those details into focus however.

Discussion:

The main focus for the long term is the potential for widespread
heavy snow on Friday and Saturday, so the discussion will
concentrate on that as the remainder of the period is uneventful.

Thursday and Thursday night, an upper ridge will be situated from
the Great Lakes southward through the Ohio valley and into the
central Gulf coast, with surface high pressure over the southern
Appalachian region. Thursday afternoon through Friday a southern
stream upper low/trough shifts east from New Mexico and west Texas,
while a northern stream disturbance moves into the upper midwest
from Canada, resulting in a strong Gulf Coast surface low and
a widespread winter weather event for the southeast CONUS.

Timing:

Thursday night lows will be in the teens to low 20s, with dewpoints
firmly in the teens if not single digits, so cold air will be
entrenched across the region to start the day Fri and precip should
start/continue as snow through the event. Sometime after daybreak
Friday, the precip shield with the developing system should be
spreading our direction from MS/AL, with snowfall likely arriving by
the mid morning hours in the Chattanooga area, midday towards the I-
40 corridor, and early afternoon in the north. Ending time looks to
be roughly 4-6 AM or so in the south, and something closer to 8-10
AM in the north. The end times could be a little premature as we
transition to a northwest flow regime Saturday on the backside of
the system, but as far as impactful snow accumulations in the lower
elevations go, those times are probably good estimates at this time.

Precip types:

The forecast reflects snow, or perhaps a few short-lived periods of
rain/snow mix, across the CWA at this time. Areas of possible
rain/snow mix at the beginning would be in the foothills of the TN
mountains as H85 flow comes over the Appalachians and warms on it`s
decent into the valley. That`s reflected in the H85 temps on some
models, but also worth noting that they`re still at/slightly below
freezing, so I think snow is the only ptype we`ll have to worry
with. If the track of the system changes, ptypes could as well, but
at this point it appears we will be dealing with only snow

Snowfall amounts:

The trends in ensemble guidance over the last 24 hours have been
upward with regards to amounts in general, and that`s especially so
with regards to probabilities of amounts greater than 4" or even 6".
First off, previous forecasts had favored a relative maxima of
snowfall amounts being in the southern valley, and lesser amounts in
the north. The trends have been to favor a spreading out of those
higher amounts across much of the CWA, with guidance now suggesting
that a widespread 3-5" snowfall is possible across the forecast
area. Additionally, the 24hr probabilities of seeing great than or
equal to 6" of snow by 7 AM Saturday have come up to non-dismissible
levels now, with some +40 percent odds across significant portions
of the CWA. All of that said, it`s still too early to really hone in
on a particular value/range as the track of this system will have
significant impacts on amounts. Suffice it to say that confidence in
a widespread winter weather event is definitively trending higher.

&&

.AVIATION...
(18Z TAFS)
Issued at 320 PM EST Tue Jan 7 2025

MVFR to VFR conditions expected at the sites, with best chance for
MVFR overnight, scattering out to VFR during Wednesday.

&&

.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN             23  38  19  39 /   0   0   0   0
Knoxville McGhee Tyson Airport, TN  19  34  15  34 /   0   0   0   0
Oak Ridge, TN                       19  34  15  34 /   0   0   0   0
Tri Cities Airport, TN              18  29  13  28 /   0   0   0   0

&&

.MRX WATCHES/WARNINGS/ADVISORIES...
NC...NONE.
TN...NONE.
VA...NONE.
&&

$$

SHORT TERM...GC
LONG TERM....CD
AVIATION...GC

[Holston_River_Rambler]

NAM looks to be coming in juiced up. 

[TellicoWx]

WSW out for West TN and N. MS

[Carvers Gap]

3 minutes ago, Reb said:

MRX disco

 

858
FXUS64 KMRX 072021
AFDMRX

Area Forecast Discussion
National Weather Service Morristown TN
321 PM EST Tue Jan 7 2025

...New SHORT TERM, LONG TERM, AVIATION...

.SHORT TERM...
(This evening through Wednesday)
Issued at 320 PM EST Tue Jan 7 2025

Stubborn clouds are slowly eroding across the Valley but may try to
return overnight. Otherwise, cold temperatures will maintain their
grip on the area tonight and Wednesday, with Valley highs again
mainly in the 30s. Expecting any overcast morning clouds to scatter
out around midday.

A mostly zonal pattern aloft will do little to dislodge the cold
surface air, but a weak disturbance may touch off some flurries
Wednesday afternoon and evening across SW VA.

&&

.LONG TERM...
(Wednesday night through next Tuesday)
Issued at 320 PM EST Tue Jan 7 2025

.LONG TERM...

Key Messages:

1. Confidence is strongly trending in favor of a significant winter
storm across the southern Appalachian region, with widespread
accumulating snow possible over the forecast area Friday into
Saturday.

2. Some uncertainties remain though - especially with regards to
amounts. Time will bring those details into focus however.

Discussion:

The main focus for the long term is the potential for widespread
heavy snow on Friday and Saturday, so the discussion will
concentrate on that as the remainder of the period is uneventful.

Thursday and Thursday night, an upper ridge will be situated from
the Great Lakes southward through the Ohio valley and into the
central Gulf coast, with surface high pressure over the southern
Appalachian region. Thursday afternoon through Friday a southern
stream upper low/trough shifts east from New Mexico and west Texas,
while a northern stream disturbance moves into the upper midwest
from Canada, resulting in a strong Gulf Coast surface low and
a widespread winter weather event for the southeast CONUS.

Timing:

Thursday night lows will be in the teens to low 20s, with dewpoints
firmly in the teens if not single digits, so cold air will be
entrenched across the region to start the day Fri and precip should
start/continue as snow through the event. Sometime after daybreak
Friday, the precip shield with the developing system should be
spreading our direction from MS/AL, with snowfall likely arriving by
the mid morning hours in the Chattanooga area, midday towards the I-
40 corridor, and early afternoon in the north. Ending time looks to
be roughly 4-6 AM or so in the south, and something closer to 8-10
AM in the north. The end times could be a little premature as we
transition to a northwest flow regime Saturday on the backside of
the system, but as far as impactful snow accumulations in the lower
elevations go, those times are probably good estimates at this time.

Precip types:

The forecast reflects snow, or perhaps a few short-lived periods of
rain/snow mix, across the CWA at this time. Areas of possible
rain/snow mix at the beginning would be in the foothills of the TN
mountains as H85 flow comes over the Appalachians and warms on it`s
decent into the valley. That`s reflected in the H85 temps on some
models, but also worth noting that they`re still at/slightly below
freezing, so I think snow is the only ptype we`ll have to worry
with. If the track of the system changes, ptypes could as well, but
at this point it appears we will be dealing with only snow

Snowfall amounts:

The trends in ensemble guidance over the last 24 hours have been
upward with regards to amounts in general, and that`s especially so
with regards to probabilities of amounts greater than 4" or even 6".
First off, previous forecasts had favored a relative maxima of
snowfall amounts being in the southern valley, and lesser amounts in
the north. The trends have been to favor a spreading out of those
higher amounts across much of the CWA, with guidance now suggesting
that a widespread 3-5" snowfall is possible across the forecast
area. Additionally, the 24hr probabilities of seeing great than or
equal to 6" of snow by 7 AM Saturday have come up to non-dismissible
levels now, with some +40 percent odds across significant portions
of the CWA. All of that said, it`s still too early to really hone in
on a particular value/range as the track of this system will have
significant impacts on amounts. Suffice it to say that confidence in
a widespread winter weather event is definitively trending higher.

&&

.AVIATION...
(18Z TAFS)
Issued at 320 PM EST Tue Jan 7 2025

MVFR to VFR conditions expected at the sites, with best chance for
MVFR overnight, scattering out to VFR during Wednesday.

&&

.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN             23  38  19  39 /   0   0   0   0
Knoxville McGhee Tyson Airport, TN  19  34  15  34 /   0   0   0   0
Oak Ridge, TN                       19  34  15  34 /   0   0   0   0
Tri Cities Airport, TN              18  29  13  28 /   0   0   0   0

&&

.MRX WATCHES/WARNINGS/ADVISORIES...
NC...NONE.
TN...NONE.
VA...NONE.
&&

$$

SHORT TERM...GC
LONG TERM....CD
AVIATION...GC

Non-dismissable levels...

[TellicoWx]

Went with 4"-6" for the WSW

 

Edit....it is tiered, browser loaded up same page for some reason.

[John1122]

NAM with 4-6 across the area at the end and still snowing across almost the entire region. 

[dwagner88]

12 minutes ago, nrgjeff said:

Morristown does not show it on their public graphic, but one can infer some East Tenn downslope from the Nashville slide. Please no. I want everyone to do well. Slide is not for commercial use. 

 

Their >4" probability chart shows it even more pronounced. It actually intrudes all the way past I-75 in Bradley and Hamilton counties. I don't buy that. Even in very intense downsloping events (IE January 2016) I don't think I've ever seen it affect more than a 10 mile strip of land along the US411 corridor down here. BTW the probabilities for >4" are as follows:

Chattanooga: 36%

Cleveland: 26%

Athens: 33%

Knoxville: 46%

Crossville: 48%

JC: 22%

Kingsport: 25%

[Carvers Gap]

2 minutes ago, dwagner88 said:

Their >4" probability chart shows it even more pronounced. It actually intrudes all the way past I-75 in Bradley and Hamilton counties. I don't buy that. Even in very intense downsloping events (IE January 2016) I don't think I've ever seen it affect more than a 10 mile strip of land along the US411 corridor down here. BTW the probabilities for >4" are as follows:

Chattanooga: 36%

Cleveland: 26%

Athens: 33%

Knoxville: 46%

Crossville: 48%

JC: 22%

Kingsport: 25%

This afternoon MRX says this:

Additionally, the 24hr probabilities of seeing great than or
equal to 6" of snow by 7 AM Saturday have come up to non-dismissible
levels now, with some +40 percent odds across significant portions
of the CWA.

[housemtnTN]

This is getting really exciting.

[fountainguy97]

59 minutes ago, tnweathernut said:

Don't get me started about this. lol  You can ask @Carvers Gapmy thoughts on downsloping/dryslot.  Was just mentioning to him this morning about the "double whammy" snow demon not everyone gets the joy of facing.  haha  

I guess when you live where we live you can never really shake it being a concern, but it's less of a concern today than it was 36 hours ago.  Trending in the right direction.  I like the trajectory of the system and the orientation of the precipitation.

Yeah I was just curious. I honestly haven't experienced many true system driven events. Vast majority of my 5 years here has been NW stuff.

the way I interpret it is a south to north element in precip trajectory can cause dry spots along the border counties. Today seems to be more of a west to east trajectory. Hoping we avoid any issues with precip lol

[TellicoWx]

ICON gonna make a run at a NAMing?

[jaxjagman]

[Reb]

[Carvers Gap]

1 hour ago, fountainguy97 said:

How concerned about dryslot/downsloping do you guys think I should be? Some earlier gfs runs that were more of a south to north orientation had a nice hole over the TN/NC border. 
 

thinking the flatter west to east we have seen more today is helping prevent that for my backyard?

Latest runs all but eliminate it.  But like tnweathernut notes, best to play that one by ear.  It is more of a disruption of southerly flow aloft by the mountains.  I don't see it as downslope or dry slot.  It looks more like a rain shadow effect.  I am sure the former plays into the rain shadow.  MRX is fully bought in to TRI getting slighted.  We'll see.  The straight line of winter storm watches along the TN/VA for this last storm left me less than enthused about that particular storm's product. I nearly got stuck on the interstate, because I followed their product for this last one.  They are rolling the dice again.  They may be right....

[Carvers Gap]

1 minute ago, Reb said:

Great share. 

My forecast range for TRI is a 57% chance of 2" of snow, or.......heavy snow.  They got it covered!  But to be far, that is kind of what modeling is showing. 

[John1122]

Euro AI is .4 minimum for the entire forecast area, that's in southern Kentucky. .45 northern areas along the border. .5 along I-40, .6+ south of 40. Ratios probably 12/13:1 north, 11-1 along 40, 10-1 south. 

[Scottie16]

Don't get me started about this. lol  You can ask [mention=769]Carvers Gap[/mention]my thoughts on downsloping/dryslot.  Was just mentioning to him this morning about the "double whammy" snow demon not everyone gets the joy of facing.  haha  
I guess when you live where we live you can never really shake it being a concern, but it's less of a concern today than it was 36 hours ago.  Trending in the right direction.  I like the trajectory of the system and the orientation of the precipitation.

TellicoWX knows all too well about it too


.

[monoptn]

I am not believing any of this until Stovepipe weighs in!

[TellicoWx]

Just now, Scottie16 said:

TellicoWX knows all too well about it too


.

Yep, no worries about downsloping (so far) here

[Bigbald]

Shew, hard to imagine  that NAM run would not have been widespread 6-12 per visual duration left..

[John1122]

Probably most concerning for far eastern areas is the dreaded downslope warming they mentioned. That would possibly see some freezing rain or sleet in those areas, as they said the surface remains below freezing. However they did say they expect all snow for everyone. 

[TellicoWx]

ICON turned the corner a hair too late...very close tho.

[Holston_River_Rambler]

RGEM looks like it will be pretty similar to 12z. 

[Scottie16]

I bet we see similar amounts to what we saw during last Januarys epic snow. 8-12 area wide!


.

[ShawnEastTN]

MEG just issued Winter Storm Watch.

 

"...WINTER STORM WATCH IN EFFECT FROM THURSDAY EVENING THROUGH LATE
FRIDAY NIGHT...

* WHAT...Heavy snow possible. Total snow accumulations between 3 and
  5 inches.

* WHERE...Portions of East Arkansas, North Mississippi, Southeast
  Missouri, and West Tennessee.

* WHEN...From Thursday evening through late Friday night.

* IMPACTS...Roads, and especially bridges and overpasses, will
  likely become slick and hazardous. Plan on slippery road
  conditions. The hazardous conditions could impact the Friday"

[John1122]

RGEM just won't lose that 725mb warm layer along the southern border that causes the sleet. The Canadian started it.  It's only on their models that shows it now. 

[housemtnTN]

2 minutes ago, Scottie16 said:

I bet we see similar amounts to what we saw during last Januarys epic snow. 8-12 area wide!


.

That would be incredible. I measured almost exactly a foot here the following morning. Back to back snow events like that for knox county I believe would be historic!

[TellicoWx]

If and  that's a big if at the moment...the system can turn sooner...someone on the eastern side will top 12"+...ICON shifted the heavy snow in Eastern NC to Western side that run. To me that's the final piece of the puzzle so to speak.