Winter Speculation 17/18 -December Thread

[Carvers Gap]

With 72 hours to go, ladies and gentlemen, that is what you call consensus.  

1.  12z UKMET/12z EURO:  Slider and OTS

2.  18z ICON/18z NAM/12z NAVGEM:  Miller A

3.  12z and 18z GFS:  Miller B/Hybrid A

I think the phrase, "All options are on the table," probably applies even at this close range.  Wow.  FWIW, my money is still on some sort of Miller A or hybrid Miller A.  And that is not worth much.

[uncheelfan]

So option 3 is what we really want correct?

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[1234snow]

18z GFS is certainly amped up this run. I could see a trend for the model to become even further amped up on future runs based on the 500mb presentation. SWVA and parts of west TN get thumped on this run.

[Holston_River_Rambler]

43 minutes ago, uncheelfan said:

So option 3 is what we really want correct?

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I think it really depends on where you are in the sub-forum. If you're in the Tri-Cities area and north and east, you can weather a Miller B better than folks south and west. Miller Bs can also be good for the western areas of TN, the upper plateau, and southern Kentucky. Where I'm at in Knoxville, I'd prefer a Miller A  with surface low tracking from New Orleans, through south Georgia and to the Outer Banks.  Miller Bs that approach from the southwest love to send a surface low up the great eastern valley as they transfer to the coast and this can cause problems with the temperatures in the lower and mid levels of the atmosphere.  

[Carvers Gap]

1 hour ago, uncheelfan said:

So option 3 is what we really want correct?

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All three work.  Option 1 is more of a mid-winter/"cold already in place" snow scenario which we do not have. A Miller A or hybrid A will work, but the low needs to track close enough but not to close, preferably through the Piedmont and just inside Cape Hatteras.

[Holston_River_Rambler]

24 minutes ago, Carvers Gap said:

All three work.  Option 1 is more of a mid-winter/"cold already in place" snow scenario which we do not have. A Miller A or hybrid A will work, but the low needs to track close enough but not to close, preferably through the Piedmont and just inside Cape Hatteras.

True.  I should have added that option 1 can be really good at that time of year, but I guess I was thinking more how out to sea the UK and Euro were at 12z with this particular storm. That's too far out to sea! 

[Carvers Gap]

Quick Weeklies update(should be the last one by me for the season and it is a good one to end the season on)...plenty of blocking, BN temps throughout the 46 day run.  Snow meteogram for Elizabethton(NE TN) looks like the dead of winter.  LOL.  No idea if correct.  But the SSW and -NAO have done their work.  Man, if that had only happened during mid-winter.

[uncheelfan]

Im just hoping that the storm system is so strong that the ull makes colder air than the models are predicting and gives all of us a paste job!!! The next 2 weeks is our window and all i want is one good storm to produce a decent snow especially for NE TN. Please Please lets reel this one in lol!!!!!

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[Carvers Gap]

I should add that I don't think we will have weeks like this week(snow showers/wind chills in the 20s) during the entire spring.  BN later in spring can still put temps in the 60s for highs...so chilly but not necessarily snowy.  I suspect we catch a warm break later this month and then maybe a reload.  Bowling ball lows will all have to be watched now.  Honestly, I like cold...not so much in April though!

[Carvers Gap]

I took a look at the Canadian Weeklies and they do support colder than normal temps through early April...BUT with warmth building from the southwest during April.  So there is that good news.

[John1122]

00z GFS drops 4-8 inches over most of Eastern Kentucky. I'll be driving across that area right around changeover if it's right. I have to be in Lexington at 10:45 and will be there 3 or 4 hours at minimum. By late afternoon Eastern KY is getting plastered. 

The NAM/Canadian do not support that solution though. 

[Holston_River_Rambler]

I feel like the EPS members improved overnight. Out of 50, I'd say most had a better 500mb look than yesterday and a few (more than yesterday at 12z) had a really nice vort. passing at a neutral tilt overhead, overnight Sunday night.  

GFS operational ups the ante and still ticks north with its surface low, with the GEFS mean surface low is still a little south. Looking at all 15 GEFS, looks to me that most are a little further south than the operational at 6z. I'd say the Canadian Ensembles look similar to the GEFS. 

NAVGEM, our compromise from yesterday, rushes an initial wave out to sea, but really tries to strengthen the 500 mb vort, pop a second low in south Georgia, and shoot it up the coast. It fails to do it though. 

UKMET is unreadable since my site for it, meteocentre, is not working for me.

12km NAM looks more like the NAVGEM in that is seems to have gone a little further south with an initial wave and is trying to pop a low from the 500 mb vort. I've also noticed the NAM likes top op random surface lows wherever it sees the strongest convection, so there's that. 

3km NAM is further north, its vort is more wound up, and still looks like it wants to go somewhere nice after the end of its run.

0z ARW2, only out to 48 hours,  looks very amped too as the vort drops through the upper midwest

6z RGEM looks like a its heading for a nice vort pass too. 

Juicier, amped mesoscales on to something since hey, its March and things may be more wound up and that seems to have been the trend with these upper lows this month?

I'll also add that this vort seems to be trending to pass overnight Sunday into Monday which can't hurt with temps. 

EDIT: forgot the 6z ICON.  It keeps the vort. wound up, but drops it to Savannah. Not before giving East TN and especially higher elevations some nice snow Monday morning as it passes.  0z ICON looked REALLY nice for East TN and SW VA

 

[Holston_River_Rambler]

I'll also add that Hi-Res short range models show a firehose of moisture shooting into SW VA overnight for almost 10 hours! In some areas this looks to fall as snow. ARW2 is the most aggressive, but its there on the NAM and RGEM. Will be interested in how this plays out for anyone that lives in that area.  I bet High Knob gets slammed. Only limiting factor I could see (and I may not be so good at reading those sounding plots on Tropical Tidbits) is that most of the frontogenetic forcing is below 700 mb (not sure if that matters since the area is also under the left exit region of a jet streak) and it doesn't look like there is full saturation into the DGZ. 

Any and all feel free to set me straight. Selfishly using this to try to learn more about using the different features on Tropical Tidbits models. 

[Carvers Gap]

Just a little bit of spread on the SREF plumes this AM.

[Holston_River_Rambler]

Interesting to note a secondary vort. at 500 mb now trailing after the first on short range, hi-res models. The secondary one has trended stronger and further west on the past few runs and is starting to interact with some Pacific energy as it rotates through. The secondary vort. starts to interact with the first one and dig the whole trough deeper and starts to give it a more neutral tilt as it passes.

12z GFS and NAM models have this 2nd vort more pronounced as it drops in. ICON 12z seems to have a piece of it but nothing near what the GFS and NAM have. The RGEM had it at 6z but as of 12z it looks a little less defined. 

This feature has only been showing up the past few runs and I'm really interested to see if it sticks around and what implications it could have as everything develops. 

Looks to me like everything is trending toward a Miller A/ hybrid (as Carvers has said) with maybe a little piece of a surface low sneaking up from Huntsville toward Chattanooga and Knoxville.  12z Euro is of course not out yet, but it looks to me like 0z overnight had groaned and lurched in this general direction. If we split the difference between the Euro/ UKMET to the south and the GFS to the north, we get a really nice Miller A track! 

[nrgjeff]

Yes the blue on the vorticity chart is NVA negative vorticity advection usually associated with ridging. Literally, negative vorticity is anti-cyclonic flow. Our friend PVA is positive vorticity advection or cyclonic flow advection.

12Z GFS just jumped on the more southern route (surface low). Key is that middle vort lobe dominating. If the first dominates, the whole thing ejects north and warm. If the very last one dominates, unlikely, things dry out. The middle one needs to prevail. 12Z NAM looks like a rogue run; I'm ignoring it. 

UPDATE: The ICON drops the hammer while the 12Z Euro has just-in-time JIT boundary layer cooling. I'm never a fan of JIT anything from severe moisture to winter cold, esp the Valley. I prefer cold air in place over JIT. Still looks good for Plateau, Mountains and probably even TRI.

Might have more of the same in coming weeks if you believe the CFS and ECMWF weeklies. Looks not cold enough for Valley snow and not warm enough for severe. Still chances at higher elevations. Cooler regime change was helped along by that SSW. Sometimes SSW linked blocking sticks around longer than other blocking. We'll see.

Was I actually hoping for the Valley? I will just start booze and basketball early. 

[Holston_River_Rambler]

At least the timing (wee hours of Monday AM) looks about as good as it could get as of now. For me in my particular my location (a whopping 900 feet in Knoxvegas) I agree with Jeff that marginal situations never seem to work out.  I'll take a hour or two of wet snow early Monday AM and a grassy inch as a win, if I can get it. Hope plateau, Tri, and SW VA come away with a bigger win. 

[John1122]

The Euro is a big hitter for North Carolina. It'd be their 3rd or 4th major snow event this year. Clearly showing why this forum was needed. Our weather is way different in winter than areas East of the Apps. They feast while we famine and vice versa. 

[uncheelfan]

It's awful quiet in here. Must be pretty much a rain event for most of our area. Im tired if seeing just flurries i want a decent accumulating snowfall. Im not askimg for a foot or anyting out of the ordinary i would be delighted with just a couple to 3 inch storm!!!!!!!

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[John1122]

Model madness abounds. The GFS transfers from East Tennessee to Savannah, Ga, dropping a little snow over North Central Tennessee and getting Kentucky in Northern and Central areas with a monster snow, also does okay in the mountains and higher spots in SWVA. Then the coastal gives North Central North Carolina a good shot of snow.

 The NAM gives 1-3 inches over Middle Tennessee and the central to southern Plateau while pounding the mountains.

The CMC is nothing for anyone and the ICON is not too far off from it.

The NAM gives the snow in Tennessee with the trailing 500mb vortex, it's further south and west than the GFS depiction. Just to the North and East of the vortex moderate snow falls. The NAM sends it from west Tennessee into Northern Alabama. That's why the Southern Plateau and Middle TN does so well. The GFS sends it from Western Kentucky into Eastern Tennessee, which is why NE of it in Kentucky gets hammered.

 

00z GFS - Heavy snow NE of the deep reds across Eastern Ky

 

00z NAM - Mod-heavy snow NE of the red in Middle Tn, South Central Plateau

[John1122]

Euro clocks Northern NC and Southern Va but doesn't do much of anything for our area. Pretty great winter on the other side of the Apps and this event might be the cherry on the cake for them.

[John1122]

MRX is kinda like "eh...model madness; ignore specific runs and watch the pattern."

 

Quote

By Sunday night, the shortwave will be swinging across the entire
forecast area. On the backside, colder air will likely bring a
change over from rain to snow, particularly in the higher
elevations. The first guess of snowfall accumulations by Monday
morning show around a half inch across the northern TN Plateau and 1
to 3 inches across the higher terrain of southwest Virginia and the
Smokys.

Another shortwave dropping out of the Great Lakes Region by early
Monday will temporarily slow the exit of the snow maker over
southwest VA. Due to the slowing nature, additional snowfall over
East TN and SW VA could bring 3 to 6 inches of snow to the highest
elevations and lesser amounts on the Plateau. Again, the models
during the season transition time sometimes have a difficult time
handling these types of scenarios. As such, confidence is still
rather low since various model solutions seem to vary greatly day to
day. However, the potential for this to happen is still very
possible.

 

[Holston_River_Rambler]

8 hours ago, uncheelfan said:

It's awful quiet in here. Must be pretty much a rain event for most of our area. Im tired if seeing just flurries i want a decent accumulating snowfall. Im not askimg for a foot or anyting out of the ordinary i would be delighted with just a couple to 3 inch storm!!!!!!!

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Speaking only for myself I'm kind of in wait and see what happens mode. I feel like all the scenarios have been discussed and shown on the models and now we wait. NAM 3k at 6z just buries the vortex into the Gulf Coast as my dreaded Canadian vortex seems to bully it south.  0z Euro, 6z GFS, ICON seem pretty similar in their overall evolution of the vortex I've been chasing in that they stretch it out and swing it through our area around Monday at 7 AM, though the 6z CMC likes the NAMs version and shunts everything south.  

Over all for me I think these things can and often have surprises at the last minute sometimes for better and sometimes for worse. Also, it is March and that may add to the surprisification.  Key for me, as it has been, is exactly how the 500 mb vortex evolves as it swings through or just south of TN.  6z 3k NAM shows how things can go very wrong and 6z RGEM shows how things can go right at least for the normally favored areas (northern plateau, southern KY, SWVA, Tri-Cities, Smokies, and elevation areas northeast).  

Edit cause I'm still poking around and drinking coffee: If I had to make a call at this point I'd favor the RGEM and GFS/ Euro. This doesn't mean snowmaggedon for any of us, but I'd say a period of wet snow Monday AM for the areas I mentioned above.  This is not just because I want someone to get something out of this, but there seems to be a trend overnight for the vortex I've been watching to interact a little with the massive vortex dropping in from the Great Lakes. Looping the RGEM at Z500 vorticity (and I could be reading this incorrectly) the vort that could bring some wet snow seems to almost be getting pulled a bit north instead of being shunted south.  I think the UKMET showed last night at 0z what might happen downstream from us if there was more interaction, but in 3 or 4 runs its gone from a shunted out to sea storm to a wound up coastal so some volatility for sure.  In reading some of the MA and NE forum area comments overnight the EPS seems to have a cluster that show something like the what the UK is showing. Still may be a whole lot of nothing but those big globals (maybe this is hearsay) don't typically move real quick. Not enough interaction for some huge storm for us, but maybe enough to keep our happy little vortex in play Monday AM.  

 

 

[Carvers Gap]

The 6z RGEM and ICON(maybe the Euro and GFS) do provide some hope in they way that they track the system. I suspect we are going to see this system track a little north at the last minute....I could be wrong.  That is a very carefully(cleverly?) worded statement by MRX regarding snowfall over E TN and SW VA - and I don't blame them.  I do agree with them that confidence is low.  I just flipped through the models...many variations including a whopper of a 6z RGEM and a whiff of the 6z NAM.  If the heaviest of this arrives at night, we have a chance.  If it is during the daytime, no dice.  March storms are notoriously fickle to predict, and this one is no different.  But I might add, they are fun to track though.  They are similar to that nice South Holston brown trout that just won't take anything, but keeps on taking surface flies.  Makes the game that much more interesting.  At this point, it does appear that this system will be elevation dependent as many March storms are, but I would not be surprised to see some surprises(even at lower elevations) where rates and bands set up(if they do indeed setup).  What makes March systems tough to predict is that sometimes they have more energy than originally predicted due to increasing day length and can have more precipitation than modeled.  I can say with complete confidence that I have no idea at this point what this is going to to do.  Like I have said before, I could just go w rain and be safe(even true during winter, but definitely during March)....but how that northern piece dives into that system is up for grabs it appears and MRX does a nice job of discussing that as well.  Temps do look marginal in the valleys, but how that piece of energy dives in during that storm sequence changes temps w each run, one way or the other.  I think the -NAO and SSW have done their work.  Otherwise, we would not be tracking this weekend's storm nor would we have seen snow in the foothills and mountains earlier this week w snow showers in the valley.  I am glad I do this for a hobby today...and don't have to make a call on this Sunday night and early Monday.  

Proud of the Vols for gutting one out last night.  Tough game against Arkansas tonight.  I think the final four of the SEC tourney are the best in the league at the moment.  UK/AL/TN/ARK will represent the forum well this weekend.  

On a final note, this spring could be a decent one for high elevation snow if the Weeklies are even remotely correct.  That was probably the second coldest run I have seen by them, so chilly that I question the run as a bit of an outlier.  But the control had many bowling ball/coast-to-coast lows.  There will be a warm-up after this weekend's system, and then it shows another significant cold spell(not January cold, but relative to norms) for April.  Fingers crossed that someone sees some snow this weekend, then a warm-up, and then watching for high elevation snows during bowling ball season.  Probably would not hurt for someone to create a spring thread after this weekend's system has run its course.  

[Holston_River_Rambler]

17 minutes ago, Carvers Gap said:

I am glad I do this for a hobby today...and don't have to make a call on this Sunday night and early Monday.  

I had the same thought this morning while typing out my bit! 

[John1122]

12z suite is getting closer to agreement. Snow axis is very close on them. The GFS and NAM slam Kentucky. The RGEM slams the Plateau. The 3K NAM gets North Central and NW Tennessee.  The ICON is a 1-2 inch event from the Plateau west to Jackson.

[Carvers Gap]

Surprised there is not much discussion.  The MAJOR news is the 12z NAM and GFS now showing a big nor'easter where there was none at 6z.  That very well could mean that the models are not done w the hybrid Miller A trend.  The CMC is a pretty good amount north of I-40...4-6" of snow.  The main news is the most models are now much stronger w/ the coastal low, and I doubt those consequences have been ironed out.  

[Carvers Gap]

Not to mention the RGEM does not look too bad on yet another run.

[Olhausen]

6 minutes ago, Carvers Gap said:

Surprised there is not much discussion.  The MAJOR news is the 12z NAM and GFS now showing a big nor'easter where there was none at 6z.  That very well could mean that the models are not done w the hybrid Miller A trend.  The CMC is a pretty good amount north of I-40...4-6" of snow.  The main news is the most models are now much stronger w/ the coastal low, and I doubt those consequences have been ironed out.  

I definitely can't help but be a little excited waking up to these model changes overnight. I'd really be excited if I lived just a little further north in middle Kentucky. This storm is looking like it could bring some surprises to some. I'm in White House so hoping those bigger totals can move down this way by go time.

[Carvers Gap]

2 minutes ago, Olhausen said:

I definitely can't help but be a little excited waking up to these model changes overnight. I'd really be excited if I lived just a little further north in middle Kentucky. This storm is looking like it could bring some surprises to some. I'm in White House so hoping those bigger totals can move down this way by go time.

Yeah, we remain just on the southwest end of where things could hold surprises.  But the big news is that the 12z suite is starting to show some major coastal solutions which would pivot the precipitation potentially over some in the forum area.  Evolving situation now.   Still plenty of uncertainty.  I suspect the Euro does not move much, but it has been slow to react this season.  I think 0z will tell the tale.  The trends now are what is important.  Are the wx models now trending towards a bigger storm?  If so, that resets some discussion.  I think a hybrid Miller A is back on the table vs the slider that has been shown.