1/10-1/12 Southern Slider

[TellicoWx]

Definitely need to keep an eye on the moisture return between 500 and 700..dry air in that area is goofing around to varying degrees across all the models. Once the comma head arrives, that issue is resolved.

[Runman292]

1 hour ago, John1122 said:

I could live with this. 

 

 

[John1122]

Euro is stuck at 18 hrs. 

[John1122]

Because we can't have nice things, the Euro is still falling apart with this, and that was just about it's worst run of all. It falls on it's face after coming out of East Texas and slowly shears out and dies. One thing you can say, no model is going to really win this, because all of them are all over the place with this potential event. I'd settle for the ICON, which is about down the middle of the UKIE/Euro vs Canadian/GFS.

[Uncle Nasty]

5 days out, I'm surprised Morristown is even mentioning amounts. That's a possible good sign. They do have Chatty with the possible dreaded WAA.





Area Forecast Discussion
National Weather Service Morristown TN
333 AM EST Mon Jan 6 2025



Discussion:

.LONG TERM...
(Tuesday through Sunday)
Issued at 254 AM EST Mon Jan 6 2025

Key Messages:

1. Cold temperatures continue through the week.

2. No significant weather through Thursday night.

4. Another good chance for wintry precipitation Friday afternoon
through Saturday.

Discussion:

Cold arctic airmass behind todays frontal system will remain locked
in across the area this week, generally running 10 degrees below
normal or more with no locations after today through Friday above 40
degrees. Nighttime lows will be mostly teens to lower 20s with skies
mostly clear and winds lighter through early Thursday night. A zonal
flow aloft will keep the middle of the week period fairly quiet.
Weak systems to the north may bring some clouds to southwest
Virginia and extreme northern Tennessee Tuesday night and Wednesday
night but no precipitation expected.

Thursday night the pattern changes as the next southern system
begins to develop. On Tuesday over the southern Rockies a surface
low pressure and an upper level low begins developing over northern
Mexico and begins to spread precipitation across the desert
southwest and west Texas Wednesday. The system continues to develop
Thursday with gulf moisture then spreading into the lower
Mississippi Valley. The ECMWF has the system more developed than the
GFS Thursday. Both models keep surface low along the coast Thursday
night and Friday. A good southwesterly flow aloft will bring the
moisture northeast into the Tennessee Valley Friday. GFS/NBM brings
a significant 2 inch or so snowfall for the Tennessee Valley and
several inches for the higher elevations especially across the
Smokies lasting through the day Saturday, but ECMWF model keeps the
heaviest precipitation along the Gulf Coast and much lighter
snowfall farther north across the CWA Friday night and Saturday
morning. Models keep temperatures cold in the 30s Friday as the
moisture moves in with slightly warmer temperatures Saturday and
Sunday. Sunday clouds decrease with the precipitation ending. Any
winter precipitation that falls through Saturday may keep high
temperatures down even with the sunshine. Will have to watch later
model runs to see if more agreement happens with the threat for
significant snow or if the system will stay farther south on the
Gulf coast. Also as a southwest flow develops out ahead of the
system and if it slows down its eastward movement temperatures may
warm more than forecast reducing potential snowfall amounts.

Sent from my SM-S916U using Tapatalk

[TellicoWx]

While the snow map looks nice on the 6z GFS, I would use alot of caution. The soundings up the valley and plateau have significant dry layer in the DGZ. If anywhere close to right that wouldn't be snow...more like a freezing rain/sleet type anywhere across East TN. Plus side is no warm nose....column is sub 32 even across the southern valley.

[TellicoWx]

Sounding from the 6z over the central valley at hr 111 (map shows snow, sounding says otherwise). For those that are new or have not read soundings much...The DGZ is the dendric growth zone, or where the temp passes between the -12 to -17 layer. To form snow flakes, that are has to saturate..if not precipitation can still form but as a rain drop instead. If temp is below freezing the rest of the way to the surface, you get sleet or even freezing drizzle. Usually happens as snow is winding down, and you get that brief period of pixy dust or icing even tho it's still 25° outside.

 

On the sounding I circled the DGZ (yellow section of the red temp line), significant dry air in that region = no snowflakes.

[Kasper]

1 hour ago, TellicoWx said:

Sounding from the 6z over the central valley at hr 111 (map shows snow, sounding says otherwise). For those that are new or have not read soundings much...The DGZ is the dendric growth zone, or where the temp passes between the -12 to -17 layer. To form snow flakes, that are has to saturate..if not precipitation can still form but as a rain drop instead. If temp is below freezing the rest of the way to the surface, you get sleet or even freezing drizzle. Usually happens as snow is winding down, and you get that brief period of pixy dust or icing even tho it's still 25° outside.

 

On the sounding I circled the DGZ (yellow section of the red temp line), significant dry air in that region = no snowflakes.

I would say we probably need to wait another run or two to let models digest the cold air and see if that trend continues! Hopefully it doesn’t 

[AMZ8990]

6z GFS snow totals for Friday/Saturday

[AMZ8990]

00z CMC onboard with the storm as well, looks like we have most of the models starting to align to a similar look/orientation.

 

[nrgjeff]

I just got back from a week-long vacation. I see y'all saved the best for later this week. Thank you!

GFS has surface warm nose problems, which is related to the DGZ* problems (few posts above). But the GFS still has greater snowfall than the Euro. What a silly model!

ECWMF has a more consistent snow profile (thickness temps) no sounding available my preferred site. EC is lighter total precip, but I prefer the EC over that GFS warm nose crap. 

*lighter precip. warmer sfc temps

[AMZ8990]

[Holston_River_Rambler]

I know it isn't for our area, but do y'all feel like the current system over performed preip. rates wise? I feel like it did. Maybe a good thing if we end up with the Euro trying to crap out as moves east. 

6z Euro vs 0z Euro:

 

I tried to to a similar comparison for the shortwaves, but giphy said it hates me and wants me to die, so you just get 6z:

 

 

 

[Met1985]

22 minutes ago, Holston_River_Rambler said:

I know it isn't for our area, but do y'all feel like the current system over performed preip. rates wise? I feel like it did. Maybe a good thing if we end up with the Euro trying to crap out as moves east. 

6z Euro vs 0z Euro:

 

I tried to to a similar comparison for the shortwaves, but giphy said it hates me and wants me to die, so you just get 6z:

 

 

 

I think we are in a much better position than currently..weak or amped going forward we still have a strong storm signal. I'd definitely like the phased part but I wouldn't mind a two small storm setup either. 

[housemtnTN]

Really hoping for some good snow totals from this system! I'm new but a longtime lurker and from what I've gathered, the system we had yesterday was likely a crapshoot for the tn valley, but this one we may have a shot for some decent snow. Wouldn't mind a repeat of last January! Don't think we'll have another one of those for a decade or more.

[Wurbus]

ICON has a light snow event across the state as it falls apart.

[John1122]

We'll see which works, but the ICON-eps ensembles have about 2x mean precip than the total precip of the OP run.

[John1122]

This one is falling apart faster than a Yugo for the eastern areas.

[John1122]

Deepening low over midlands of South Carolina and it can't generate any qpf on the NW side so far.

[Wurbus]

Like John said, it kinda falls apart over our area, but that turns into a monster for parts of the NE. 2'-3' of snow for parts of New Jersey and NYC. 969 low sitting just off the coast before it goes to sea.

[Carvers Gap]

I think we are going to see a significant winter storm over a good portion of the forum area.  I could be wrong.  But that GFS run cranks.  It definitely has some pieces the E TN peeps won't want, but the CMC is an entirely different solution.  The GFS is basically a dry slot in a comma head.  It is not so much that it falls apart as we get dry slotted.  The dry slot bullseye is going to move around some.  But the 12z suite brings frozen to most counties in our forum area.  I really, really don't want what the CMC is dishing.   However, that is a very plausible outcome, and fits climatology.  

[nrgjeff]

There is a risk of a handoff debacle, you know when the Olympic relay runners drop the baton. 

However I'm not going to fret over that on the ECMWF yet 5 days out. I'll still take the Euro risk over the GFS surface warm surface nose rubbish. The latter is particularly annoying. Just get the cold air locked in for once!

Getting back to the current system, yeah @Holston_River_Rambler it over achieved in a few areas. KCMO had thunder snow. That's always a big score. 

[Carvers Gap]

LOL.  Jeff got it first....

The other thing that we are seeing is some energy transfer from the eastern valley to the Piedmont.  This has the chance to be a major winter storm form here to the Northeast.  These types of storms often don't have details worked out until the storm is actually under way.  I have been dry slotted when there was no dry slot forecast.  I have been hammered when modeling jogged one way or the other at the last minute.  I highly doubt that modeling even remotely has the specifics worked out.  The generality is there is likely a winter storm affecting millions.  The specifics of "who" not so much.

[Hurricaneguy]

Fully convinced this will be a whole lotta nothing for East TN. I was in the warm nose last Jan. Still salty about it. Winters are just not the same anymore. 

[Matthew70]

Crazy how cold it is today.  This is definitely making it to where any frozen precip will stick. 

[Carvers Gap]

The 12z GEFS is coming in south of the deterministic not unsurprisingly.  Could it be the deterministic is trending faster than the ensemble can catch up?  Absolutely possible.  But...until that deterministic locks in, I roll with the ensemble even this late in the game.  So far, the 12z GFS is an outlier.  Now, it can score a coup.  We just saw that happen.  However, it is oscillating from amped to GOM slider with each run.  

Recommendation for now....just blend the major operational models.  That will get us pretty close.  The dry slot is a problem for E TN, but not on all modeling.  Downscoping is almost always a problem with slp on the coast.  When it is an inland runner, precip can overcome that since it is closer to the storm center.

Modeling is trying to get a handle on what could be a pretty big storm for many areas in the East.

[John1122]

Snow mean is nice board wide on the GEFS.

[Windspeed]

Fully convinced this will be a whole lotta nothing for East TN. I was in the warm nose last Jan. Still salty about it. Winters are just not the same anymore. 

ETN needs the cold surface and 850 hPa airmass to hold in place and cooperate. We're in the 120 hr range now. We may still get a warm nose, but I am hopeful the upper Holston Valley will remain cold enough. If rates are weak with low QPF, we probably lose. If rates can pump up the column, we win. Therefore, the 10-11 system may come down to the wire before we know the cutoff of the graupel vs heavy snow line. Going to require a little patience until it plays out. Curbing my expectations and perhaps the Eastern Valley gets a surprise.

[Carvers Gap]

Correction...I don't think the 12z GEFS is south.  The precip shield has expanded pretty significantly.  Track is generally the same.  

[Carvers Gap]

@Holston_River_Rambler, would it be possible for you go gif the "MSLP + Member Low Locations"  from say 60-150 hours for the 12z GEFS?  That is the one where all of the low members are one, single map.  I have been using the East Coast view FWIW.  That will give everyone a really good idea of the good and bad with the ensemble layout.  

Of note, you all can see a faint shadow of energy go through middle TN, a low in the Lakes, and predominantly most lows around Savannah.  IF there is an energy handoff, the energy would handoff to Savanah from TN.  I have seen that happen, but that is really rare.  The model shows a pretty decent signal for a coastal only, but not a guarantee.  The lows in the Lakes....yep, a problem.  That is probably what is wrecking thermals in the E TN valley.