Historic Christmas Cold & maybe snow?! Dec 23rd-30th

[TellicoWx]

Kentucky Gov. advising people to get to where they are going by Thurs afternoon and plan to stay there until Mon possibly.

[fountainguy97]

Models really drying this front up as it makes its way across. EURO may end up correct after all haha

[PowellVolz]

Models really drying this front up as it makes its way across. EURO may end up correct after all haha

energy transfer maybe?


.

[Daniel Boone]

10 minutes ago, fountainguy97 said:

Models really drying this front up as it makes its way across. EURO may end up correct after all haha

Shouldn't surprise us. That far SE System yesterday hogged a decent amount of moisture from our south. The system off the coast will zap some toward it. Not alot to work with. 

[Daniel Boone]

1 hour ago, John1122 said:

The craziest thing to me is my high is predicted to be 6 Friday for the daytime, and 14 for Saturday but nothing below 0. Rare to get daytime highs in the single numbers and stay above 0.

Yeah. You can bet if skies clear and winds subside they'll be below zero reading's one or two of the mornings. 

[TellicoWx]

Also have to take into account the downsloping off the plateau. For east Tennessee area, the only places i look to have anything of possible significance is the plateau and east of Hwy 411 toward the foothills/mountains. 

[Silas Lang]

25 minutes ago, TellicoWx said:

Also have to take into account the downsloping off the plateau. For east Tennessee area, the only places i look to have anything of possible significance is the plateau and east of Hwy 411 toward the foothills/mountains. 

That's my guess. Downsloping. Seems pretty consistent with topography. Counties directly bordering the plateau to the east get the worst shaft. 

[John1122]

Gonna choose to hug the HRRR for now. The higher the resolution the model, the better for mby. It may be finding the low atmosphere level snow better. These are simulated radar runs and snow will be falling from atmosphere levels lower than the radar can find in some cases. 

[TellicoWx]

MRX upgrades entire area to Windchill Warning:

WIND CHILL WARNING IN EFFECT FROM 4 AM EST /3 AM CST/ FRIDAY
TO 1 PM EST /NOON CST/ SATURDAY...

* WHAT...Dangerously cold wind chills expected. Wind chills 10 to
  20 below zero lower elevations, and as low as 25 to 35 below
  zero at the higher elevations.

* WHERE...Southwest North Carolina, east Tennessee and southwest
  Virginia.

* WHEN...From 4 AM EST /3 AM CST/ Friday to 1 PM EST /noon CST/
  Saturday.

* IMPACTS...The cold wind chills could cause frostbite on
  exposed skin in as little as 30 minutes.

* ADDITIONAL DETAILS...Wind gusts Thursday night through Friday
  are expected to be between 30 and 50 mph. Winds this strong may
  result in downed trees and power lines, which may cause power
  outages while temperatures are extremely cold.

[ShawnEastTN]

Also have to take into account the downsloping off the plateau. For east Tennessee area, the only places i look to have anything of possible significance is the plateau and east of Hwy 411 toward the foothills/mountains. 

I think downsloping plays a part in most anafrontal situations, but the flow in most anafrontal situations is more w to nw. The flow post fropa is mostly modeled as due north, while that still contends with downslope, I question how much it affects the situation being from that direction instead of W to NW. I think this storm is a unicorn of sorts without a standard analog to compare. I think most of what we are seeing with qpf as modeled with the southern extent of the precip generally speaking is that its drying up as it moves east.

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[Runman292]

Speaking of historical cold, when was the last time all of TN had a wind chill warning?

[Jed33]

28 minutes ago, TellicoWx said:

MRX upgrades entire area to Windchill Warning:

WIND CHILL WARNING IN EFFECT FROM 4 AM EST /3 AM CST/ FRIDAY
TO 1 PM EST /NOON CST/ SATURDAY...

* WHAT...Dangerously cold wind chills expected. Wind chills 10 to
  20 below zero lower elevations, and as low as 25 to 35 below
  zero at the higher elevations.

* WHERE...Southwest North Carolina, east Tennessee and southwest
  Virginia.

* WHEN...From 4 AM EST /3 AM CST/ Friday to 1 PM EST /noon CST/
  Saturday.

* IMPACTS...The cold wind chills could cause frostbite on
  exposed skin in as little as 30 minutes.

* ADDITIONAL DETAILS...Wind gusts Thursday night through Friday
  are expected to be between 30 and 50 mph. Winds this strong may
  result in downed trees and power lines, which may cause power
  outages while temperatures are extremely cold.

I can’t recall ever seeing  WC Warning since I’ve lived in E TN! Advisory yes, only warnings for the mtns. Takes a lot for MRX to issue one for the valley 

[Jed33]

19 minutes ago, Runman292 said:

Speaking of historical cold, when was the last time all of TN had a wind chill warning?

I don’t recall a statewide one either! Maybe in the 80’s but it’s been awhile.

[Wurbus]

At least I got the historic cold part right in the thread name.....

[PowellVolz]

I think downsloping plays a part in most anafrontal situations, but the flow in most anafrontal situations is more w to nw. The flow post fropa is mostly modeled as due north, while that still contends with downslope, I question how much it affects the situation being from that direction instead of W to NW. I think this storm is a unicorn of sorts without a standard analog to compare. I think most of what we are seeing with qpf as modeled with the southern extent of the precip generally speaking is that its drying up as it moves east.

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This was my thoughts on the downslope issues. My area of the valley doesn’t have downslope issues with a NNW wind.


.

[Carvers Gap]

1 minute ago, Wurbus said:

At least I got the historic cold part right in the thread name.....

If many get an inch or two of snow.....you get them both.  Honestly, with as wild as this is about to get(tropical storm force winds and sharp temp drop)....the thread will deliver.

[ShawnEastTN]

MRX afternoon disco is up. I noticed my point forecast snow accumulation increased, not by much from less than .5", to less than an inch so decided to check if they had the discussion up, MRX mentions they were slightly increasing snowfall amounts due to WPC guidance. Good read though.

https://forecast.weather.gov/product.php?site=NWS&issuedby=OHX&product=AFD&format=CI&version=1&glossary=1



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[Carvers Gap]

Just eyeballing, the Happy Hour run of the GFS looks a bit more robust mid-state.

[Wurbus]

2 minutes ago, Carvers Gap said:

If many get an inch or two of snow.....you get them both.  Honestly, with as wild as this is about to get(tropical storm force winds and sharp temp drop)....the thread will deliver.

Yeah. I do think the plateau, and west of it, will get an inch or two. Most of us in the valley will probably get half an inch or so. The extreme temp drop will likely catch a lot of people off guard, but at least that will happen overnight while most people are in bed.

[jaxjagman]

RGENT - WINTER WEATHER MESSAGE
National Weather Service Nashville TN
242 PM CST Wed Dec 21 2022

TNZ005>011-023>034-059-062>066-078-080-220900-
/O.NEW.KOHX.WW.Y.0010.221223T0000Z-221223T1200Z/
/O.EXT.KOHX.WC.W.0001.221223T0400Z-221223T1800Z/
Stewart-Montgomery-Robertson-Sumner-Macon-Clay-Pickett-Houston-
Humphreys-Dickson-Cheatham-Davidson-Wilson-Trousdale-Smith-
Jackson-Putnam-Overton-Fentress-Williamson-Rutherford-Cannon-
De Kalb-White-Cumberland-Warren-Van Buren-
Including the cities of Dover, Clarksville, Springfield,
Hendersonville, Gallatin, Goodlettsville, Lafayette, Celina,
Byrdstown, Erin, Tennessee Ridge, Waverly, New Johnsonville,
McEwen, Dickson, Ashland City, Kingston Springs, Nashville,
Lebanon, Mount Juliet, Hartsville, Carthage, South Carthage,
Gordonsville, Gainesboro, Cookeville, Livingston, Jamestown,
Allardt, Franklin, Brentwood, Murfreesboro, Smyrna, La Vergne,
Woodbury, Smithville, Sparta, Crossville, McMinnville,
and Spencer
242 PM CST Wed Dec 21 2022

...WINTER WEATHER ADVISORY IN EFFECT FROM 6 PM THURSDAY TO 6 AM
CST FRIDAY...
...WIND CHILL WARNING NOW IN EFFECT FROM 10 PM THURSDAY TO NOON
CST FRIDAY...

* WHAT...For the Wind Chill Warning, dangerously cold wind chills
  expected. Wind chills as low as 15 below to 25 below zero. For
  the Winter Weather Advisory, snow expected. Total snow
  accumulations of one half to two inches...with local amounts of
  3 inches along the northern Cumberland Plateau. Winds will gust
  as high as 35 mph.

* WHERE...roughly the northern half of Middle Tennessee.

* WHEN...For the Wind Chill Warning, from 10 PM Thursday to noon
  CST Friday. For the Winter Weather Advisory, from 6 PM
  Thursday to 6 AM CST Friday.

* IMPACTS...Plan on slippery road conditions. The hazardous
  conditions could impact the morning commute. The cold wind
  chills could cause frostbite on exposed skin in as little as
  30 minutes.

* ADDITIONAL DETAILS...Given the fast rate of cooling behind the
  arctic front...some flash freezing will be possible whereby all
  exposed wet surfaces will freeze immediately.

[Carvers Gap]

Can anyone tell if there would be lightning w those bands just east of Nashville on the GFS 18z?

[ShawnEastTN]

RGENT - WINTER WEATHER MESSAGENational Weather Service Nashville TN242 PM CST Wed Dec 21 2022TNZ005>011-023>034-059-062>066-078-080-220900-/O.NEW.KOHX.WW.Y.0010.221223T0000Z-221223T1200Z//O.EXT.KOHX.WC.W.0001.221223T0400Z-221223T1800Z/Stewart-Montgomery-Robertson-Sumner-Macon-Clay-Pickett-Houston-Humphreys-Dickson-Cheatham-Davidson-Wilson-Trousdale-Smith-Jackson-Putnam-Overton-Fentress-Williamson-Rutherford-Cannon-De Kalb-White-Cumberland-Warren-Van Buren-Including the cities of Dover, Clarksville, Springfield,Hendersonville, Gallatin, Goodlettsville, Lafayette, Celina,Byrdstown, Erin, Tennessee Ridge, Waverly, New Johnsonville,McEwen, Dickson, Ashland City, Kingston Springs, Nashville,Lebanon, Mount Juliet, Hartsville, Carthage, South Carthage,Gordonsville, Gainesboro, Cookeville, Livingston, Jamestown,Allardt, Franklin, Brentwood, Murfreesboro, Smyrna, La Vergne,Woodbury, Smithville, Sparta, Crossville, McMinnville,and Spencer242 PM CST Wed Dec 21 2022...WINTER WEATHER ADVISORY IN EFFECT FROM 6 PM THURSDAY TO 6 AMCST FRIDAY......WIND CHILL WARNING NOW IN EFFECT FROM 10 PM THURSDAY TO NOONCST FRIDAY...* WHAT...For the Wind Chill Warning, dangerously cold wind chills expected. Wind chills as low as 15 below to 25 below zero. For the Winter Weather Advisory, snow expected. Total snow accumulations of one half to two inches...with local amounts of 3 inches along the northern Cumberland Plateau. Winds will gust as high as 35 mph.* WHERE...roughly the northern half of Middle Tennessee.* WHEN...For the Wind Chill Warning, from 10 PM Thursday to noon CST Friday. For the Winter Weather Advisory, from 6 PM Thursday to 6 AM CST Friday.* IMPACTS...Plan on slippery road conditions. The hazardous conditions could impact the morning commute. The cold wind chills could cause frostbite on exposed skin in as little as 30 minutes.* ADDITIONAL DETAILS...Given the fast rate of cooling behind the arctic front...some flash freezing will be possible whereby all exposed wet surfaces will freeze immediately.

I'm surprised MRX hasn't pulled the trigger, not so much about snow amounts, as much as the combination of flash freeze, light snow and wind chill combined makes for dangerous travel right at high travel days.

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[jaxjagman]

National Weather Service Nashville TN
249 PM CST Wed Dec 21 2022

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

.SHORT TERM...
(This afternoon through Friday Night)
Issued at 243 PM CST Wed Dec 21 2022

The good news first, tonight looks mostly dry, maybe a few light
sprinkles here and there as our lower levels moisten up. Should be
quite mild, with low temps in the upper 30s to lower 40s. Rain
chances will reach our northwestern areas around midday on Friday
and increase from there with the arctic front on approach. Highs
should reach the 50s area wide. Not bad, but now the bad news.

I`m looking north across western Canada, and its across the Southern
Yukon territory where a 1061 MB surface high resides. Temperatures
in that vicinity are between -50F and -60F. As the Canadian
ground truth has continued to feed into the models, we are
trending toward slightly colder temperatures. A few of the outlier
models show low temps as cold as 9 below zero for Nashville
Friday morning. This is just an outlier however, and my official
low will be +3F, with many zero degree lows for many northern
areas. The wind gradient still looks quite strong, in fact it is
ticking up up a bit as well. Latest wind chill values are forecast
to be close to 20 below zero for much of the mid state Friday
morning. High temperatures will reach just 7F to 10F over our
northern and central Plateau and 10F to 15F elsewhere. The wind
chill warning shall continue but it is now in effect for Thursday
night at 10 PM until Noon on Friday. We still may need to look at
a potential regular wind advisory for Thursday night, especially
for those first several hours following the arctic fropa. This may
be issued in upcoming shifts perhaps.

The arctic fropa itself is still expected around 5PM in our far
northwest, 7p to 8p for Nashville and the I-65 corridor, and 10Pm
along the Plateau.

As for the snow potential, that has ticked up a bit as well. The
upper trough will feed the post frontal air with added energy as it
continues to show a slight negative tilt. Furthermore, strengthening
as well as the track of the vort max has lead to more favorable
snowfall amounts. The snowfall window will occur roughly just behind
the arctic fropa and continue for several hours. We do not meet
blizzard conditions because the snowfall wont be heavy enough to
reduce the visibility down to 1/4Sm for at least 2 consecutive hours.
That said, expected snowfall amounts will range from 1/2 inch to 2
inches across roughly the northern half of the cwa. There could
very well be some localized 3 inch amounts along the higher
elevations of the northern Cumberland Plateau. For this reason, we
will be issuing a winter weather advisory for the northern half,
roughly along a line from Humphreys county to Van Buren county and
points north. The advisory will be in effect from 00Z Friday
until 12Z Friday.

Moving on, The cold weather will continue through Christmas and wind
speeds will still be somewhat elevated with low wind chill values.
On Monday we have a chance to reach above freezing, with lower to
mid 30s expected. Low temperatures will be in the single
digits Saturday morning as well.

&&

.LONG TERM...
(Saturday through next Wednesday)
Issued at 243 PM CST Wed Dec 21 2022

In the extended forecast, it looks dry with a warming trend. We will
approach 50 for highs for the middle of next week.

[matt9697]

Just now, jaxjagman said:

National Weather Service Nashville TN
249 PM CST Wed Dec 21 2022

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

.SHORT TERM...
(This afternoon through Friday Night)
Issued at 243 PM CST Wed Dec 21 2022

The good news first, tonight looks mostly dry, maybe a few light
sprinkles here and there as our lower levels moisten up. Should be
quite mild, with low temps in the upper 30s to lower 40s. Rain
chances will reach our northwestern areas around midday on Friday
and increase from there with the arctic front on approach. Highs
should reach the 50s area wide. Not bad, but now the bad news.

I`m looking north across western Canada, and its across the Southern
Yukon territory where a 1061 MB surface high resides. Temperatures
in that vicinity are between -50F and -60F. As the Canadian
ground truth has continued to feed into the models, we are
trending toward slightly colder temperatures. A few of the outlier
models show low temps as cold as 9 below zero for Nashville
Friday morning. This is just an outlier however, and my official
low will be +3F, with many zero degree lows for many northern
areas. The wind gradient still looks quite strong, in fact it is
ticking up up a bit as well. Latest wind chill values are forecast
to be close to 20 below zero for much of the mid state Friday
morning. High temperatures will reach just 7F to 10F over our
northern and central Plateau and 10F to 15F elsewhere. The wind
chill warning shall continue but it is now in effect for Thursday
night at 10 PM until Noon on Friday. We still may need to look at
a potential regular wind advisory for Thursday night, especially
for those first several hours following the arctic fropa. This may
be issued in upcoming shifts perhaps.

The arctic fropa itself is still expected around 5PM in our far
northwest, 7p to 8p for Nashville and the I-65 corridor, and 10Pm
along the Plateau.

As for the snow potential, that has ticked up a bit as well. The
upper trough will feed the post frontal air with added energy as it
continues to show a slight negative tilt. Furthermore, strengthening
as well as the track of the vort max has lead to more favorable
snowfall amounts. The snowfall window will occur roughly just behind
the arctic fropa and continue for several hours. We do not meet
blizzard conditions because the snowfall wont be heavy enough to
reduce the visibility down to 1/4Sm for at least 2 consecutive hours.
That said, expected snowfall amounts will range from 1/2 inch to 2
inches across roughly the northern half of the cwa. There could
very well be some localized 3 inch amounts along the higher
elevations of the northern Cumberland Plateau. For this reason, we
will be issuing a winter weather advisory for the northern half,
roughly along a line from Humphreys county to Van Buren county and
points north. The advisory will be in effect from 00Z Friday
until 12Z Friday.

Moving on, The cold weather will continue through Christmas and wind
speeds will still be somewhat elevated with low wind chill values.
On Monday we have a chance to reach above freezing, with lower to
mid 30s expected. Low temperatures will be in the single
digits Saturday morning as well.

&&

.LONG TERM...
(Saturday through next Wednesday)
Issued at 243 PM CST Wed Dec 21 2022

In the extended forecast, it looks dry with a warming trend. We will
approach 50 for highs for the middle of next week.

I would be surprised if we did not dip negative tomorrow night and Friday night, especially if we put a couple inches snow on the ground

[PowellVolz]

Can anyone tell if there would be lightning w those bands just east of Nashville on the GFS 18z?

Ive been playing golf so I haven’t looked good but I read yesterday somewhere that some of the meso mods were showing 25 to 50 joules at the surface post cold front across the state. Now I didn’t go confirm it but I was thinking out loud that some of the stronger snow squalls might have 30-40mph winds in them especially across the plateau. If that was true about the surface instability, I was thinking that might help fight off any downsloping in the valley.


.

[Carvers Gap]

5 minutes ago, PowellVolz said:

Ive been playing golf so I haven’t looked good but I read yesterday somewhere that some of the meso mods were showing 25 to 50 joules at the surface post cold front across the state. Now I didn’t go confirm it but I was thinking out loud that some of the stronger snow squalls might have 30-40mph winds in them especially across the plateau. If that was true about the surface instability, I was thinking that might help fight off any downsloping in the valley.


.

It is possible we could get downsloped west of 75 and 81.  It happens with big coastal storms but the opposite side of the valley.  I would be really surprised if anything slowed this front down.  I have been monitoring web cams on the front range today.   Even the folks in those areas are impressed.  

[Holston_River_Rambler]

MRX did go with the jet enhancing frontogenesis for the forcing mechanism wrt the front so hopefully that is a good sign for snowfall. I mean, it isn't the big story and it ain't a lot of snow, but even a crust would make the arctic chill more enjoyable for me. 

[Carvers Gap]

@Wurbus, if that map below isn't worthy of a thread....I don't know what is.  

[ShawnEastTN]

What is interesting to me if snow amounts are more even a small amount more say 3" with the wind as strong as its going to be and the powdery nature of this type of snow, there could be times of serious visibility issues with near whiteout conditions from blowing snow. Would be amazing to see if we end up with more than currently forecast.

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[Scottie16]

Just now, ShawnEastTN said:

What is interesting to me if snow amounts are more even a small amount more say 3" with the wind as strong as its going to be and the powdery nature of this type of snow, there could be times of serious visibility issues with near whiteout conditions from blowing snow. Would be amazing to see if we end up with more than currently forecast.

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You know the guys up in Morristown are stressing right now on issuing anything. If we had just a tad bit more moisture available we’d fall under blizzard criteria even with 2-3 inches.