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

[Carvers Gap]

But...we are going to have to see it get some support.  It is on an island with that run.  So, all caveats apply when looking at clown maps of one outlier run.  Let's hope it is the beginning of a trend.  The run does make sense though.

[tnweathernut]

5 minutes ago, Carvers Gap said:

Addendum...that map is heftier due to upslope which follows in the 24 hours after the front.  Many areas north of I-40 pick up 1-2" more in the bitterly cold air that the precip falls into.

Christmas Day 2020 was more special for me than the rain changing to snow that fell Dec 24th……. The wrap around produced very heavy snow at times here in N Johnson City.  Was beautiful.

[tnweathernut]

6 minutes ago, Carvers Gap said:

Addendum...that map is heftier due to upslope which follows in the 24 hours after the front.  Many areas north of I-40 pick up 1-2" more in the bitterly cold air that the precip falls into.

Christmas Day 2020 was more special for me than the rain changing to snow that fell Dec 24th……. The wrap around produced very heavy snow at times here in N Johnson City.  Was beautiful.

I will add, it was also not well modeled very far in advance…….

[PowellVolz]

Christmas Day 2020 was more special for me than the rain changing to snow that fell Dec 24th……. The wrap around produced very heavy snow at times here in N Johnson City.  Was beautiful.
I will add, it was also not well modeled very far in advance…….

You can say that again


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[Knoxtron]

 

 

[PowellVolz]

 
 

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[Knoxtron]

19 minutes ago, PowellVolz said:

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[Stovepipe]

40 minutes ago, Knoxtron said:

 

[Wurbus]

I love looking at the difference in temps on model runs with this front....whether we score with any snow or not, it is impressive

[Stovepipe]

 

That's a white Christmas for much of the forum area considering likely ratios.

[Carvers Gap]

Pretty significant upslope signal for NE TN and SE KY. 2-3" fall after the initial front.  Let's see if it has any support.  This is basically the same set-up as 6z, just a little bit less juice.  There are some changes to the overall storm.  As this nears the coast, we could see one final switch-up in modeling, and that may account for the changes we just saw.

 

[Stovepipe]

I'm really sorry for the animals and homeless people that will have to brave this.

[Carvers Gap]

I think it is reasonable to say that there is potential for some snow with this front.  Could be flurries.  Could be snow showers.  Could be light to moderate snow.  The CMC has it, but likes middle TN more.  The one thing I noticed is the 12z sped up the second storm quite a bit, and the spacing between the first and second storms decreased by quite a bit.  Upper middle/west TN continue to be in the consensus sweet spot w/ NE TN being a wild card - may depend on totally on upslope(not good for MBY but good for areas east of I81).  I highly doubt modeling is anywhere close to nailing down ana front amounts if those do indeed occur.  While I don't trust the GFS at all past d7, it seems a bit more adaptable than other modeling w/ stronger storms in close range.  Good test upcoming.  I would not be surprised to see it score a coup, though amounts were slightly lower this go around.

[Carvers Gap]

Tagging onto @Stovepipe

[Carvers Gap]

For posterity.  Departures from normal and not actual temps.  12z GFS...

 

[ShawnEastTN]

Usually in anafrontal snow chasing rain situations if you are in the Great Valley of East Tennessee you painfully watch and wait for the cold to spill over the plateau it creates a daming that slows the cold and allows moisture to exit before the cold spills over meaning we often get ripped off. However I think this may be the strongest arctic front I can remember in at least a decade, and with the pressure gradient I don't think the plateau will hold the cold back and create the delay we often see. This likely has high potential to bust higher in the Great Valley than normal anafrontal events of the past, keeping in mind though that most anafrontal events for the valley of east Tennessee are dusting to an inch type of events for most, so to bust higher doesnt mean crazy amounts but still potentially higher than most anafrontal events. Kind of excited to see this transpire, definitely not our everyday arctic front scenario.

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[Carvers Gap]

32 minutes ago, ShawnEastTN said:

Usually in anafrontal snow chasing rain situations if you are in the Great Valley of East Tennessee you painfully watch and wait for the cold to spill over the plateau it creates a daming that slows the cold and allows moisture to exit before the cold spills over meaning we often get ripped off. However I think this may be the strongest arctic front I can remember in at least a decade, and with the pressure gradient I don't think the plateau will hold the cold back and create the delay we often see. This likely has high potential to bust higher in the Great Valley than normal anafrontal events of the past, keeping in mind though that most anafrontal events for the valley of east Tennessee are dusting to an inch type of events for most, so to bust higher doesnt mean crazy amounts but still potentially higher than most anafrontal events. Kind of excited to see this transpire, definitely not our everyday arctic front scenario.

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This thing is coming like a freight train.  

[PowellVolz]

Usually in anafrontal snow chasing rain situations if you are in the Great Valley of East Tennessee you painfully watch and wait for the cold to spill over the plateau it creates a daming that slows the cold and allows moisture to exit before the cold spills over meaning we often get ripped off. However I think this may be the strongest arctic front I can remember in at least a decade, and with the pressure gradient I don't think the plateau will hold the cold back and create the delay we often see. This likely has high potential to bust higher in the Great Valley than normal anafrontal events of the past, keeping in mind though that most anafrontal events for the valley of east Tennessee are dusting to an inch type of events for most, so to bust higher doesnt mean crazy amounts but still potentially higher than most anafrontal events. Kind of excited to see this transpire, definitely not our everyday arctic front scenario.

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One thing that will also help (or hurt) is we are dealing with mid 40’s for several days before the snow starts instead of mid 60’s which is more typical. My point is there will be a wet ground with temps falling into the mid teens with snow showers. A 1/2 to 1” of snow will make the roads a disaster.


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[ShawnEastTN]

One thing that will also help (or hurt) is we are dealing with mid 40’s for several days before the snow starts instead of mid 60’s which is more typical. My point is there will be a wet ground with temps falling into the mid teens with snow showers. A 1/2 to 1” of snow will make the roads a disaster.


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Agree, this will probably be the worst rapid freeze up we've had in many, many years. The wet surfaces will rapidly become encased in ice then covered in whatever amount of snow we get. This could be one of the worst events for roadways in quite a long time and of course occurring on a high travel period. I fully expect winter weather products to be issued by all the regions NWS offices for the freeze up during high travel days even if we get only an inch or less snow.

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[John1122]

A baby step, but the UKIE went from absolutely no snow in Tennessee to .5 to 1 inch across most of the Western 2/3rds and far Eastern Mtns.  I believe it really struggles with post frontal snow and I am not sure it ever caught on to Christmas 2020.

[John1122]

Very small step on the Euro as well. Wasn't a lot but it was a slight increase from 00z last night.  It just cuts everything off really fast. That's actually not super common with powerhouse arctic fronts, they usually squeeze out every last drop of moisture. It just wraps in an incredible amount of dry air. The GFS has 80 percent RH at 700mb over me at 102, the Euro 12 percent RH. The Canadian has 60 percent.

[John1122]

Its going to be a midnight high on all models. We will struggle to escape the single digits to low 10s Friday during daylight hours.

[Silas Lang]

50 minutes ago, John1122 said:

Very small step on the Euro as well. Wasn't a lot but it was a slight increase from 00z last night.  It just cuts everything off really fast. That's actually not super common with powerhouse arctic fronts, they usually squeeze out every last drop of moisture. It just wraps in an incredible amount of dry air. The GFS has 80 percent RH at 700mb over me at 102, the Euro 12 percent RH. The Canadian has 60 percent.

This is a good point. Regardless of how much snow we actually get, there should definitely be some lingering showers and flurries. It will definitely be a good winter day in the least. 

[PowellVolz]

Its going to be a midnight high on all models. We will struggle to escape the single digits to low 10s Friday during daylight hours.

I really think there will be some extra energy and lift moving through the flow that the mods won’t pick up on. I also think lapse rates will be high enough that downsloping won’t kill the valley like it usually does. I haven’t looked hard enough at the projections of the placement of the low but my location does best when the flow is more NNW than your typical NW. Anything west of you John that turns towards the valley usually dries up when it clears Anderson Co.


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[ShawnEastTN]

Something else to note until this powerhouse storm gets through models will have a hard time seeing any clippers or energy diving out of the plains behind the storm. Think we still have potential for something after the storm, but before troughing eases back.

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[Knoxtron]

Not sure how much is matters but looking at the Euro progression, seems to be very consistent on the surface freezing line passage time. However, the depth of the cold immediately behind the front has become more stout... prob changes next run lol

 

 

 

[PowellVolz]

MRX is starting to downplay the backside snow. Not that they ever played it up or anything but they are saying the mods are trending away from snow. I haven’t been able to looked deep into the mods but reading this board gave me the impression that we held steady or maybe got a little better today.


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[ShawnEastTN]

MRX is starting to downplay the backside snow. Not that they ever played it up or anything but they are saying the mods are trending away from snow. I haven’t been able to looked deep into the mods but reading this board gave me the impression that we held steady or maybe got a little better today.


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Agree, guess they view GFS as a bit of an outsider or 18z trended less.

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[matt9697]

3 minutes ago, PowellVolz said:

MRX is starting to downplay the backside snow. Not that they ever played it up or anything but they are saying the mods are trending away from snow. I haven’t been able to looked deep into the mods but reading this board gave me the impression that we held steady or maybe got a little better today.


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Nashville is doing the same thing, maybe if they all say it then it will come true 

[Jesse from KY]

3 minutes ago, PowellVolz said:

MRX is starting to downplay the backside snow. Not that they ever played it up or anything but they are saying the mods are trending away from snow. I haven’t been able to looked deep into the mods but reading this board gave me the impression that we held steady or maybe got a little better today.


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NWS Jackson is currently thinking around an inch overall:

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Presently, snowfall amounts look to be around an inch.
Snowfall amounts are very dependent on the track which could change
drastically based on the final track of the low.