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

[Carvers Gap]

Winds 40+mph, wind chills -10F to -20F, light snow.  That is winter at its best for December.  It's beginning to feel a lot like Christmas....or Fairbanks, Alaska.  

 

 

[Carvers Gap]

Interesting to see the mention of ZR in NE TN.  The CMC nailed that if right.  Otherwise, this is for posterity.  MRX afternoon disco:

Wendesday night into Thursday morning there is a possibility for a
brief window of freezing rain in the far northeastern TN counties
and SW VA as isentropic ascent leads to precip spreading back into
the area from the south and southeast. Not expecting any impacts as
precip amounts will be light, and increasing southeasterly flow will
also yield some downslope warming. Regarding those winds, some
models show 40-50kt flow around the 850mb level, which could yield
some high winds in the mountains and foothills. However there`s
enough uncertainty here about whether we even reach advisory
criteria, that we will hold off on any wind headlines for Wed night
into Thu morning. On Thursday a 500 mb low dives through the upper
plains and midwest, into the Ohio Valley just north of our area,
driving a strong cold front eastward into the region Thu night. More
rain will spread into the forecast area ahead of this Thu evening.

The front is expected to cross our area quickly during the overnight
hours, between 06Z and 09Z. Temperatures will drop abruptly - and I
mean very abruptly - immediately following this frontal passage,
causing rain to transition to snow. This will occur between midnight
and 3-4 am Friday morning, with temperatures falling through the
day. Friday high temperatures will likely occur at or just after
midnight, and temps will drop into the teens and single digits by
the time you are waking up on Friday. Models suggesting anomalous
850 temps ranging from -25C to -27C. These dangerously cold
temperatures will persist through the weekend and are not expected
to climb above freezing again until Monday afternoon.

In regards to snow amounts: only light amounts are anticipated,
trace to 1" in most places, higher in mountains. Despite the minimal
snow accumulations expected, the concern continues to be any
precipitation or pre-existing rain on the roads freezing to the
roadways which would be supported by the incredibly low temps. The
frigid air fills in behind the front and will squeeze out any last
precip, so isolated to scattered flurries and snow showers remain
for Friday. Storm total snow is only a few hundredths of an inch
across the valley, with higher totals around 0.75-1.4" in SW VA and
in the mountains

Late Thursday night and into Friday a Wind Advisory may be necessary
as forecast wind gusts are expected to be 20-30+kts in the valley,
and 25-35+ kts in the higher elevations. Piggy backing off of the
that, another main concern with this system is the subsequent
dangerously low wind chills due to the bitter cold and elevated wind
speeds. Forecast wind chills on Friday are as low as -10 and even
-20 in some higher elevations, which may also warrant a Wind Chill
 Advisory, and possibly a Wind Chill Warning beginning Friday
 morning. Will leave that to future shifts.

To summarize: our main message continues to be the threat of
dangerously cold temperatures and wind chills, as well as the
potential for travel impacts following the cold frontal passage and
arrival of frigid air Thursday overnight.

 

[fountainguy97]

Can't get behind the GFS. 3KM NAM paints a .5-1" swatch across the state.  I think it's a novelty event.

There is very little NW flow of any kind associated with this event. It's nearly all frontal. And even that is in question.  Should be a very very minor snow event looking at things this afternoon. Gfs is in need of an emergency shutdown and repair. Maybe this will age poorly lol

 

12z  euro and GFS still have the same qpf. One is frozen one is not.
 

Main show is the sheer amount of cold we will have Friday. 

[Carvers Gap]

18z GFS does not budge.

[Holston_River_Rambler]

If anyone is looking for a reason to hug the NAM this afternoon during happy hour, you could consider that it has been trending ever so slightly from a purely N --> S precip shield associated with the arctic front to one that is more SSW --> NNE.

I feel like that orientation is better for any anafrontal sort of lift for precip. 

 

 

[John1122]

We are still maybe 24 hours from the NAMRGEM wheelhouse on these type of events. I expect the GFS to either throw in the flag or get others onboard in 36 hours or so.

[Daniel Boone]

2 minutes ago, John1122 said:

We are still maybe 24 hours from the NAMRGEM wheelhouse on these type of events. I expect the GFS to either throw in the flag or get others onboard in 36 hours or so.

Exactly. Nam3k at this range performed terrible at my location Winter before last. Heck, it even did right before each event ! If it had been right, 80% of the Snow we got would if been Rain. 

[fountainguy97]

Gfs is certainly some eye candy. 
 

legit death band with temps plummeting. Places are getting smoked with 6" in 3hrs or less.

[Reb]

3 minutes ago, fountainguy97 said:

Gfs is certainly some eye candy. 
 

legit death band with temps plummeting. Places are getting smoked with 6" in 3hrs or less.

[fountainguy97]

20 minutes ago, John1122 said:

We are still maybe 24 hours from the NAMRGEM wheelhouse on these type of events. I expect the GFS to either throw in the flag or get others onboard in 36 hours or so.

On a positive note it is very encouraging to see the NAM favor the GFS with most of the precip behind the cold front. NAM has a long range dry bias. So maybe it'll beef up in time.

[John1122]

It's at the very end of it's range but the RAP has most of it's moisture behind the front with the storm diving SE.

[jaxjagman]

1 hour ago, Holston_River_Rambler said:

If anyone is looking for a reason to hug the NAM this afternoon during happy hour, you could consider that it has been trending ever so slightly from a purely N --> S precip shield associated with the arctic front to one that is more SSW --> NNE.

I feel like that orientation is better for any anafrontal sort of lift for precip. 

 

 

 Miles City, Montana could possibly break the HP record if the NAM is right.This is where the record HP (1064) WAS recorded Dec 24 1983.Least the NAM is showing it around that area(1069)

[Carvers Gap]

8 minutes ago, jaxjagman said:

 Miles City, Montana could possibly break the HP record if the NAM is right.This is where the record HP (1064) WAS recorded Dec 24 1983.Least the NAM is showing it around that area(1069)

Glad you mentioned that.  Yeah, multiple runs on the GFS have had it.  That would be something to behold.  I read where several ski slopes are shutting down due to the extreme temps forecast in Montana.  Those cats don't close their slopes much due to cold, especially during the holiday season.  So, when they are taking precautions due to the cold....legit cold stuff.

[jaxjagman]

6 minutes ago, Carvers Gap said:

Glad you mentioned that.  Yeah, multiple runs on the GFS have had it.  That would be something to behold.  I read where several ski slopes are shutting down due to the extreme temps forecast in Montana.  Those cats don't close their slopes much due to cold, especially during the holiday season.  So, when they are taking precautions due to the cold....legit cold stuff.

Wonder how cold it could actually get that way.Nothing that extreme has been ever digested in the models?See the GFS SHOW -31/-32,thats brutal enough

[jaxjagman]

1 minute ago, jaxjagman said:

Wonder how cold it could actually get that way.Nothing that extreme has been ever digested in the models?See the GFS SHOW -31/-32,thats brutal enough

Edit  GFS does have a 1067 last run

[beavis1729]

28 minutes ago, jaxjagman said:

Wonder how cold it could actually get that way.Nothing that extreme has been ever digested in the models?See the GFS SHOW -31/-32,thats brutal enough

NWS Great Falls mentioned in their AFD that valley locations could drop to -40 or colder under the high pressure, and that many automated thermometers may not be accurate since they are only calibrated to -40.

[Carvers Gap]

29 minutes ago, beavis1729 said:

NWS Great Falls mentioned in their AFD that valley locations could drop to -40 or colder under the high pressure, and that many automated thermometers may not be accurate since they are only calibrated to -40.

I looked at Sheridan, WY, and they have wind chills head to -40.  But -40 on the thermometer w/ wind chills is gonna get crazy.  

[Carvers Gap]

1 hour ago, jaxjagman said:

Wonder how cold it could actually get that way.Nothing that extreme has been ever digested in the models?See the GFS SHOW -31/-32,thats brutal enough

Yeah, it's rare air.  I know everyone likes snow, but to get to witness this type of extreme in December is something we don't see every season.  I looked at Cut Banks' wind chills and they are showing -50F.  

[PowellVolz]

NWS Great Falls mentioned in their AFD that valley locations could drop to -40 or colder under the high pressure, and that many automated thermometers may not be accurate since they are only calibrated to -40.

Minnesota has valleys?


.

[fountainguy97]

Deep dive into the model differences.

 

There are a couple slight differences between gfs and euro. The most prominent is that the 500mb vort is further south and in a better alignment to funnel cold our way on the gfs.  (The gfs just has a better cold push) We need to see this heavy negative tilt persistent on the GFS. I believe that orientation is a large reason that our cold push is ahead of the moisture vs behind. The gfs has a scooping trajectory that really helps accelerate our cold into the region. The EURO is more of a Linear trajectory not to mention much further north.. This goes for all levels as well.

the NAM is leaning toward the GFS on the trajectory at 500mb but not fully there.  We want to see the gfs hold it's southern most vort trajectory and even tick further south. It is our main driver for moisture.

The GFS is also just straight up more energetic with our moisture. Possibly due to our Vmax convo from above.  But it's 925-700mb moisture is a tap straight from the Great Lakes with the Gulf side aiding transport on the front line. The EURO has a much more anemic transport across all areas.

 

00z we want to see the GFS vort trajectory stay or even tick south. They are prone to ticking one way or the other up until go time.  I'm probably not understanding the root cause but rather just seeing the surface levels but that's just what my untrained eye sees right now.

 

[ShawnEastTN]

Minnesota has valleys?


.

Montana, there are so many 'M' states and their abbreviations are so similar. Though Minnesota does have valleys, albeit low relief valleys.

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[John1122]

16 minutes ago, PowellVolz said:

Minnesota has valleys?


.

They've got several mountains up to around 2300 feet. It actually looks similar to this area in spots. 

[PowellVolz]

Montana, there are so many 'M' states and their abbreviations are so similar. Though Minnesota does have valleys, albeit low relief valleys.

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Geez… my bad lol


.

[PowellVolz]

They've got several mountains up to around 2300 feet. It actually looks similar to this area in spots. 

I had no idea. I assumed it would be like Iowa, Nebraska etc…. Makes me wonder now if there’s hills in states I thought where basically flat. That’s a beautiful picture though


.

[PowellVolz]

Deep dive into the model differences.
 
There are a couple slight differences between gfs and euro. The most prominent is that the 500mb vort is further south and in a better alignment to funnel cold our way on the gfs.  (The gfs just has a better cold push) We need to see this heavy negative tilt persistent on the GFS. I believe that orientation is a large reason that our cold push is ahead of the moisture vs behind. The gfs has a scooping trajectory that really helps accelerate our cold into the region. The EURO is more of a Linear trajectory not to mention much further north.. This goes for all levels as well.
the NAM is leaning toward the GFS on the trajectory at 500mb but not fully there.  We want to see the gfs hold it's southern most vort trajectory and even tick further south. It is our main driver for moisture.
The GFS is also just straight up more energetic with our moisture. Possibly due to our Vmax convo from above.  But it's 925-700mb moisture is a tap straight from the Great Lakes with the Gulf side aiding transport on the front line. The EURO has a much more anemic transport across all areas.
 
00z we want to see the GFS vort trajectory stay or even tick south. They are prone to ticking one way or the other up until go time.  I'm probably not understanding the root cause but rather just seeing the surface levels but that's just what my untrained eye sees right now.
 

You really helped me a lot right here. I haven’t been able to dig in with the mods because of work, so I’ve been trying to catch-up as I can. Thanks


.

[Stovepipe]

The NAM is all over the place with the timing and amount of precip.  Like John said, it's still early for that model.  It'll be interesting to see where it settles the next couple of runs.

 

[ShawnEastTN]

I had no idea. I assumed it would be like Iowa, Nebraska etc…. Makes me wonder now if there’s hills in states I thought where basically flat. That’s a beautiful picture though


.

Pretty much 3/4 of Minnesota is exactly how you picture it. The hilly area is mostly far northern Minnesota especially nearest to Lake Superior in the Arrowhead/Iron region.

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[BlunderStorm]

@fountainguy97Just adding to what you said,

18z GFS for 1 AM Friday juxtaposed with the 12z EURO's front placement (difference highlighted) and negative tilt (in dotted yellow). Some of the difference is in the speed of progression but some of it is indeed the cold hitting harder overrunning the precip.

As an aside interestingly the Euro has Iowa roughly 10F colder at the same hour.

[Scottie16]

0Z NAM seems to be following suite with the GFS.

[BlunderStorm]

6 minutes ago, Scottie16 said:

0Z NAM seems to be following suite with the GFS.

At this range I'm not sure if that is a positive or a curse.
But yeah, I like what we're seeing with the more robust anafrontal precip.