2016-2017 Great Tennessee Valley Winter Discussion

[John1122]

The GFS is starting to hint there cold be some snow all along the NW side of the precip shield. It has some 1+ inch dots in SW Tn showing up. The Canadian is 1-3 from the N Plateau to NETN/SWVA. 

I think the NW edge of the precip shield will be snow at some points, especially at elevation. It will have a tough time sticking though. Sort of like the clipper a while back. It snowed enough to have accumulated 3-4 inches but less than half that stuck.

OHX write up below. I won't bother with MRX, per usual they seem to believe that snow can't fall from the sky when temperatures are above freezing. I never saw a drop of rain from that clipper with temps in the 38 degree range at the start of the precip. Also had 8 inches of snow at 35 a few years ago when they forecast nothing but rain because temps were in the mid 30s.

Quote

Models have expanded precip chances a bit earlier than previous
runs, and now have precip sneaking into the mid state on Tuesday.
The upper low that will be over TX on Tuesday will creep eastward
and phase with the upper trough over the Great Lakes region by mid
day Wednesday. Rain chances move in Tuesday morning for western
areas, and expands eastward during the day. Currently the I-40
corridor has chance pops during the day, with the rest of the
area seeing schc for now. Best shot overall will be overnight
Wednesday just as the shortwave trough phases with the larger
trough to the north. The cold front from the larger northern
trough will also be entering the region overnight Tuesday into
Wednesday, and may drop temperatures enough for some mixed
precipitation. 850mb temps have dropped a bit each run between the
models, and if that trend continues, having mention of a mix of
frozen precip types may need to be added to the forecast. It seems
the shortwave over the region now phasing with the larger upper
trough is helping bring colder air in early enough while precip is
ongoing. Currently, 850mb temps drop below 0C just as most of the
precip is exiting the region Wednesday morning, but still have
mention of a rain/snow mix on the Plateau where temps look to be
cold enough. Again, if the cooling trend continues within the
models, frozen precip chances will have to be expanded westward
from the Plateau during the early morning hours Wednesday.

 

[Carvers Gap]

Will be interesting to see the weeklies tonight...the 0z liked cold going back west and bleeding eastward in waves.   What happens in November the winter will remember, right?  Looks like that pattern may return. I still like the time frame between Feb 25 through the first week of March as a period of potential cold and storminess.  I do not think it will be cold the entire time.   A potential active GOM track is shown developing on the GFS.   Not sure if that is real or not.  The GEFS cannot be trusted as it has shown a perpetual cool down in d+10 for a couple of weeks.  

[weathertree4u]

35 minutes ago, Carvers Gap said:

Will be interesting to see the weeklies tonight...the 0z liked cold going back west and bleeding eastward in waves.   What happens in November the winter will remember, right?  Looks like that pattern may return. I still like the time frame between Feb 25 through the first week of March as a period of potential cold and storminess.  I do not think it will be cold the entire time.   A potential active GOM track is shown developing on the GFS.   Not sure if that is real or not.  The GEFS cannot be trusted as it has shown a perpetual cool down in d+10 for a couple of weeks.  

I know I just read over what you guys say more so than what the local weather people say. Too often it seems that they just repeat, sometimes verbatim, the morning forecast discussion from the NWS, which of course is not bad but there seems to be little thought involved. I can recall as a kid watching the weather from Bill Hall, he was the man! Back then, mets had to draw on the Lows and Highs on the wipe off board when they did the live weather, there was much more "experience" involved over modeling. Likely modeling was in its infancy in the late 70's and 80's not sure when that came on the scene really.

 

[Carvers Gap]

JB did mention(finally and after my earlier posts for the record) a lag for temps to respond to the MJO.  In my opinion, the weather on the east coast has lagged in response to the MJO by roughly one week(sometimes up to ten days) this winter.   We should be in phase 8 today or tomorrow according  to Daculawx.  We need it to make it to phase 1 for a storm in the east.  So, wee will see how the wx looks in 7-10 days.   Then, we shall see if the MJO loops back quickly.  JB did make a convincing case that the SOI is about to fall as heights are predicted to rise north of Australia, 

[Carvers Gap]

53 minutes ago, *Flash* said:

Basically, some snowflakes may mix in early Wednesday, but we'll need the precip shield to swoop in earlier during max cooling and hope for some colder trends the next 24-36 hours. I guess north fringe residents in higher elevations may see some brief stickage, but like Carver mentioned, my attention can't help but hone in on the d10 'threat'. And yes, like Admiral Ackbar warned, it's a trap. I know. Can't help it. I'm a hesitant punter I guess.

Yeah, we just like sticking our hand on a hot stove.  Can't get enough pain.  Been a death star of warmth this winter....need a proton torpedo down the exhaust port to save it, i.e. late season winter storm.   I do like seeing the track out of the GOM on repeated GFS runs.  That is how things used to be...reocurrring rains or snows originating from a GOM/nor'easter track.  I count four-ish on the 12z alone.  

[Carvers Gap]

As much as we like to give models a hard time...they have been decent this winter.  When have they shown a consistently decent winter threat inside of five days only to take it away?  The LR models have struggled in the LR and have given a couple of false positives for cold...but inside of ten days the operationals have been generally warm.  We have had little to track and rightfully so w record warm January and February weather.

[Carvers Gap]

That was a wonky run of the 12z Euro...finally gets a low on the trailing front.  Then it falls off a cliff.  Yes, I know I said the models were doing well.  Just because a run is wonky does not mean the model is bad. The Euro can take a few runs to shift.  The 12z was a major break in continuity...and not necessarily in a bad way.

[BlunderStorm]

Even that is pushing it Flash and I am about as far north and elevated as this forum generally goes. I am expecting flurries mixed with rain. Low Expectations are the best policy especially this late in the game. As for the rain 2017 has been a soaker so far with 9 inches of rain in the last 30 days according to my rain gauge.

[nrgjeff]

Tuesday night, especially early Wednesday morning, I like some light snow Upper Plateau into northeast Tennessee (TRI). Even MRX may have boundary layer issues though. NAM Op is a little warm and too moist south. NAM Para gets colder faster north of I-40/81/26. It also picks up on subtle forcing coming out of Kentucky. Should benefit east Kentucky highlands and southwest Virginia too. BNA cold will probably be tardy. TYS probably stays too warm. No chance CHA. However the elevation based forecast favors Upper Plateau to TRI and adjacent KY/VA.

[Daniel Boone]

Excellent post Jeff! Pretty much what I'm thinking as well. Was gonna make a post when got time. Glad you mentioned the Nam warm bias. Also when looking at 2m maps some want to take that as ground level here. The entire board tn valley area is higher than that.

[1234snow]

Tuesday night, especially early Wednesday morning, I like some light snow Upper Plateau into northeast Tennessee (TRI). Even MRX may have boundary layer issues though. NAM Op is a little warm and too moist south. NAM Para gets colder faster north of I-40/81/26. It also picks up on subtle forcing coming out of Kentucky. Should benefit east Kentucky highlands and southwest Virginia too. BNA cold will probably be tardy. TYS probably stays too warm. No chance CHA. However the elevation based forecast favors Upper Plateau to TRI and adjacent KY/VA.

Jeff do you envision snow in the early morning hours in SWVA/NETN at elevations below 1,500 feet?

[Carvers Gap]

Weeklies...last one of the season for me unless there are changes.  Feb 25 - March 3 look like a decent pattern at 500mb and is reflected as such by 850 temps.  As we have often seen this winter, the 2m temps on the model do not correspond to the pattern at 500...and often the model has been correct in showing that.  Proceed at your own risk...  Looks like a stormy timeframe w some potential.  Plenty of energy sliding under a mean eastern trough...eventually the trough retrogrades to the nation's midsection....will comment more later.  Some may argue that the storm pattern west of the Apps is decent until mid-March.  Temps due to climo and pattern will be an issue that can only be ironed-out event by event.  Would think the mtns might do well above 3,500'.

[Carvers Gap]

0z 3 km NAM is pretty interesting for SW VA and the mountains there and E TN.

[BlunderStorm]

57 minutes ago, Carvers Gap said:

0z 3 km NAM is pretty interesting for SW VA and the mountains there and E TN.

A somewhat significant heavy wet snowfall localized over us. A type of event which will leave a large amount of the public unaware due to the lack of hitting any (major) population centers. I must say after seeing how the models have unfolded after the last few hours my view has changed. There is a chance this may unfold after all. NAM 4km is less enthusiastic about the snow. NAM isn't bad. RDPS affects just SWVA . GFS has the low a little stronger and little further north over Atlanta at hour 36 resulting in snow lingering for a greater amount of time, good for SWVA not good for TRI.

[John1122]

We'll see if the HI-RES NAM is sniffing something out. It appears to really change areas over to heavy snowfall due to heavy precip rates. That would likely cause some top down cooling of the column. I've seen it happen before. 3-5 inches of snow above a certain elevation, all rain below. Very sharp cut off both north to south and elevation wise.

[John1122]

Most models are showing 1-3 inches for my area tonight. I would love to get the surprise. Could be some heavy rates in areas that do change over. If nothing else maybe I can drive up a little and see some snow.

[BlunderStorm]

On the latest NAM 3km the cold arrives later however the precipitation shield improves quite a lot. The other models still remain down to Earth.

 

[AMZ8990]

1 hour ago, BlunderStorm said:

On the latest NAM 3km the cold arrives later however the precipitation shield improves quite a lot. The other models still remain down to Earth.

 

Do you really trust the NAM??

[BlunderStorm]

53 minutes ago, AMZ8990 said:

Do you really trust the NAM??

       To be honest, no. Do I think we have a chance at that validating? yes. Do I think it is likely? no. From very limited but still valuable knowledge the short term HRRR is what I prefer and it is just now gaining relevancy for what we are speaking of. The 4km has been a lot less volatile with smaller but still notable impacts. For those of us elevated north of I-40 it is worth a look. The GFS while no longer the model of choice at this range seems promising, the same applies with the Canadian. If we can get enough cooling from the snowfall it may stick to some degree but if it remains light and scattered for a long period I don't see anything sticking other then on the highly favorable mountains above 3000ft. It is not so much the likelihood of it being significant as it is the lack of warning the public has. No winter weather Advisories from the NWS. None from Morristown, Charleston, Blacksburg or other and WCYB for the most part dismissed it. (IF... ) the cards on the table are played just right we may see more then a trace. I don't think a thread for it is appropriate considering it affects a fraction of the sub-forum.

Also earlier in the morning I saw a few flakes falling believe it or not. Did anyone else?

[1234snow]

I never like these marginal situations and this one is as marginal as it gets. Elevation snows never work out in my location and in the surrounding Tri-Cities but after this winter maybe we can get a little lucky. Just watching some snow fall would be nice right now.

[Daniel Boone]

IF precip does move in this afternoon, it is possible evaporative cooling may help us all out as dews are now in the 20's in much of the area. However, if precips not heavy enough, it may just be virga for the most part with the relatively low humidity mid-lower levels..

Agree with you blunder on the lack of acknowledgement from nws offices. Should at least have a special wx statement out detailing possibility. Especially, making note of higher elevations snowfall potential.  The last system comes to mind, as the nws plainly said NO snow accs in the elevated towns of norton to gatlinburg  after changeover. They said above 3500 ft only. We had reports of half inch to an inch from 1400 ft on up in Lee and Wise county.       

 

[BlunderStorm]

35 minutes ago, Daniel Boone said:

IF precip does move in this afternoon, it is possible evaporative cooling may help us all out as dews are now in the 20's in much of the area. However, if precips not heavy enough, it may just be virga for the most part with the relatively low humidity mid-lower levels..

Agree with you blunder on the lack of acknowledgement from nws offices. Should at least have a special wx statement out detailing possibility. Especially, making note of higher elevations snowfall potential.  The last system comes to mind, as the nws plainly said NO snow accs in the elevated towns of norton to gatlinburg  after changeover. They said above 3500 ft only. We had reports of half inch to an inch from 1400 ft on up in Lee and Wise county.       

 

Morristown at the bottom of their report for weather hazards briefly mentions 1-3 inches overnight for areas at or above 3000ft. Nothing mentioned for lower lying areas.

[John1122]

The NAM knocked the other model's socks off on the clipper, especially on temp profiles. It's a razor thin situation. Reminds me of the event in December 2009 when I had 8 inches of heavy wet snow and every direction around me was mostly rain. I just happened to get under a very heavy precip area that caused just enough dynamic cooling to turn to snow. Once it did the snow was extremely heavy and allowed the atmosphere to stay just cold enough for snow. I could see somewhere managing that. Especially elevations at or above 2000 feet. I think 3500 and up are almost a lock for snow. LeConte will possibly get it's best event of the whole winter. 

The 3k and the RGEM are insistent on snow falling. The HRRR and RAP are close to the end of their range with it. But are also showing Plateau/SE Ky/SWVA/Mountains snowfall.

[Carvers Gap]

I like the EPS d10-15.  Whether it verifies I don't know...but that sort of looks like winter.  

[BlunderStorm]

It is easy to become doubtful of positive signals for winter weather past 10 days given how our winter has been.

[Carvers Gap]

The models handled this storm really well.  Snowed and rained where predicted.

[BlunderStorm]

I would have to agree for the most part. The low lying clouds and wet snow have made for some pretty images as well.

[nrgjeff]

Agree the models did well.

2 hours ago, Carvers Gap said:

The models handled this storm really well.  Snowed and rained where predicted.

Almost always one can make a manual adjustment toward snow Upper Plateau. Models correctly went no this time. Models also had the yes TRI/VA. Short-term and hi-res NWP continues to improve even while the GFS continues to degrade, lol.

Welp. when's the next chance of severe on the Euro?

[EastKnox]

So being new to all of this an soak it all in, am I right in saying that there is potential phasing of pieces of energy below?  And if so, this would be a potential weather-maker for us?

[Carvers Gap]

4 hours ago, EastKnox said:

So being new to all of this an soak it all in, am I right in saying that there is potential phasing of pieces of energy below?  And if so, this would be a potential weather-maker for us?

Looks like it phases over PA/NY.  But yes, that is a phase or at least a partial phase.  Western energy goes to Michigan while the southern piece strengthens on the frontal boundary of the Michigan energy.  The southern piece races northward and is absorbed.  That has been there for many runs and probably is not completely ironed-out in its details.  Lows over the GL area usually mean no snow here.  Looks like 850s crash...but too late.  Definitely worth watching if not just for the curiosity of being interested in how this plays out.  Could be a blizzard for the Plains and/or MidwesrMidwest depending on how the details work out.  I hold out slim hopes here...but they are indeed slim.