Spring/Summer 2018 Mid to Long Term Discussion.

[Carvers Gap]

@1234snow ...like clockwork.    Thunder in the mountains during winter -> snow within two weeks.  I know...I know...it is spring, but still funny nonetheless.  Winter storm watches up in the mountains of North Carolina and SW VA.  WWA for those in SE KY.

.LONG TERM (Tuesday night through Monday)...We start the period with
an area of low pressure swinging across the forecast area with
ongoing light rain showers in place. As the low pulls east Tuesday
night, colder air will advect into the region with stout nw flow
behind the low. As temperatures drop through the night, rain will
transition over to snow. The highest elevations will see snow as
early as 00Z Wednesday. The snow line will quickly work its way down
in elevation and areas around 3000/4000 feet should be seeing snow
by roughly 03z. Depending on which model you look at, snow could
start as early as 09Z for some valley locations and by 12z at the
latest. Depending on how quickly the rain transitions over to snow
in valley locations will determine the amount of accumulation, if
any. As of now it looks like our favored upslope terrain, above 5000
feet, could see 2 to 4 inches with up to 6 across areas such as
Mount LeConte, Sam`s Gap, and Roan Mountain. Areas between 2000 and
4000 feet 1 to 3 inches. Portions of the northern plateau, northeast
TN, and southwest VA up to an inch in some valley locations. Where a
dusting is possible across the central valley. We will continue to
watch this system closely, especially as soon as we get past our
severe weather event moving through tonight. A mountain zone winter
weather advisory is likely with the next forecast update tomorrow
morning. Light snow showers still in place Wednesday morning but
tapering off by late morning for the valley. Light snow showers will
linger on and off across the high terrain through the day. Highs on
Wednesday are the coldest of the period with highs in the upper 30s
to mid 40s. A few light snow showers could even linger into
Wednesday night due to the upslope flow. Lows overnight will be in
the mid to upper 20s for most.

 

[John1122]

I expect to get an inch or so if this comes through at night. Possibly even more than that. If nothing else I should be able to go above 2500 feet for a few inches.

[John1122]

00z suite so far, 2-4 inches of snow falls across portions of the area, I'd expect 1/4th-1/2 that to manage to stick if it gets heavy during the night. If during the day time I'd expect it to coat the ground briefly during heavy showers but melt off at times.  

[Holston_River_Rambler]

I agree with John, elevation and night will work wonders with this one. 

Some oddities though: 

Scott County, VA not in a WWA from MRX?? Don't know that I've ever seen that if Lee and Washington County, VA are in one.  Jeff mentioned in the Winter Spec. thread, it's not just a NW Flow, (MRX in their AM discussion has even mentioned that beautiful phrase, "deformation zone") so even though some of the Hi-Res models show the central valley of East TN getting downsloped, I'm wondering if the radar verifies a little more fulsomely here. Also, there is a lot of energy floating around and interacting aloft, so wonder if there might be some squally surprises.  For me in Knoxvegas just seeing some snow fall would be nice, getting a coating on grassy surfaces (the wording I used to hate) would be a solid win.   

The rest of this speculation is only aimed at SW VA, from Abingdon then N and E

All high-res models are showing a strong area of precip developing over SW VA this evening near Marion and Wytheville as a strong short wave at 500 mb starts to go negative over the TN Valley (really nice location for many of us if it wasn't March 20). This upper energy consolidates with other pieces coming in from the NW and cuts off over central KY. Also, I learned earlier in the winter from following "crankyweather guy" that sometimes there can be a heavy band of snow along a little front? that forms as energy from a low transfers to the coast. Not sure at all about this part, but it looks to me to be part of what's enhancing the precip I'm talking about since a primary low is dying over WV and a new one is forming along the coast and there seems to be a line of enhancement between the two. The precip (as of 6z models) looks to be so strong that it quickly cools the column and changes everything over to snow. Looks dynamic to me, so maybe thundersnow where this happens? Almost entirely out of our subforum area, but if this moves just a hair back to the SW, maybe Blunderstorm and others in the far NE reaches of SW VA can get in on it? Either way it looks fun to watch develop and maybe even on webcams.  The NAM is, as perhaps you'd expect the most amped, but ARW2, RGEM show a similar process.  

[Carvers Gap]

Just flipped through he overnight model suite and morning 6z run.  I have been watching this for some time.  Just have not written much as I think most were getting weary of the snow talk during what should be spring. (If you want to see a broken record....just go look at the BN temps on the Weeklies.  On the bright side, it does finally show seasonal temps by late April.) March snows are notorious for surprises and difficult in forecasting.  I generally just look at it like this...mountains (as usual) get more but the discrepancy is usually much more.  The Valley is a total crap shoot - as there are multiple drivers for snow there but elevation is the issue and time of day. This system is tricky.  Many of the short range models have a slp developing in the lee of the Apps which is partly energy transfer and partly just a vortex rotating into the area.  Big takeaway is decent amount of energy rotating through as it cools off.  MRX has a great write-up this AM BTW.  I wasn't going to include it, because it was so long...but it is truly a good write-up. 

<Begin MRX quote>
The cold air behind the frontal passage will allow the rain
showers to change to snow showers across the higher terrain first
this evening, and then into the Plateau overnight. For the valleys
of southwest Virginia and northeast Tennessee and gradual change
over to snow showers is expected early Wednesday morning.

Due to low-level instability, orographic lift, and deformation
zone wrapping around upper low, a prolonged period of snow showers
are expected across the area through Wednesday evening. Snow
accumulations will be elevation dependent given the relatively
warm ground and strong ultra-violet radiation melting snowfall.

Have issued a winter storm warning for the higher elevations of
southwest Virginia, such as High Knob, and the far eastern
Tennessee Mountains. Places like the higher terrain of the Smokys
will likely see the greatest snow accumulations.

Light snow accumulations are also possible over the lower
elevations of southwest Virginia and northern Plateau. May need to
issue a winter weather advisory there later this morning.

Besides the snow, freezing temperatures are expected area-wide for
Wednesday night/Thursday morning. A freeze watch will likely be
issued later today.

.Long Term (Thursday through Monday)...
Temperatures will remain around 10 degrees below normal with
northerly/northwesterly flow bringing in colder and drier air. After
a brief break from precipitation chances during the day on Thursday,
chances ramp back up Thursday evening/night. A shortwave will move
in from the northwest and bring out next chance at precipitation.
With the temperatures expected to get near or just below freezing on
Thursday night/Friday morning we can`t rule out the possibility of
additional winter weather. Right now the best chances look to be in
the higher terrain and NE Tennessee and SW Virginia...But as usual
with these events a lot will depend on the temperatures overnight,
so potential snowfall amounts at this time are a bit tricky. But
currently widespread heavy snowfall is generally not expected in our
forecast area.
<End MRX quote>

Here is the Euro map from 0z and it looks reasonable if maybe not slightly too hefty for the Valleys and underdone in the mountains.  That is to be expected by a global model.

[BlunderStorm]

The trick in getting this heavy snowfall would be in getting the temperatures down faster which I'm not too confident will occur. I have never understood the significant difference in temperature between the New River Valley and Holston/Clinch River Valleys. This difference in temperature is usually between Marion and Wytheville as well as between Tazewell and Bluefield. It can prove to be quite significant and I have noticed over the years as my weather awareness has increased. Keep in mind there is no mountain range separating the towns just the flow of streams in the two valleys with Clinch mountain running parallel. The 3km NAM, RGEM, and HRRR all show this very well for tonight with a sharp temperature gradient.  Similar to what happened last week I speculate a late change over in the early morning will happen that hangs on through the day snowing but perhaps not accumulating. Perhaps finally amounting to an inch or more after dark. Areas east of me will likely see their totals increase drastically over a short distance. I am not sure how scattered the snow will be on the back side, high resolution models from a glance do in fact seem more scattered and less as a shield of precipitation but it may be wrong.

[Carvers Gap]

The 12z 12kNAM also shows a shift northward w the snow shield which is a very normal trend with spring storms.  Still, plenty to watch.  Really, I am hoping the mountains see something as I am willing and able to travel if the roads are clear...and of course if there is snow in them thar hills.

[Carvers Gap]

I should add that the 12kNAM will likely verify as the snow hole is right over my local, and Chattanooga is also without snow.  I have seen this movie before.  Any snow is bonus snow at this point...flurries, snow showers, or for a lucky few..accumulation.  When I lived in JC for a few years, March seemed to always hold a few surprises.  

[BlunderStorm]

Yep you weren't kidding Carver this run of the NAM

is certified by the Kingsport Snow Hole of Approval... 

[Holston_River_Rambler]

57 minutes ago, BlunderStorm said:

I have never understood the significant difference in temperature between the New River Valley and Holston/Clinch River Valleys. This difference in temperature is usually between Marion and Wytheville as well as between Tazewell and Bluefield.

Yeah, I've always noticed there are two zones in the eastern subforum areas that seem to be geographic boundaries for weather. The first is the one you mention. It's like there's a balance point somewhere along I-81. Maybe just high enough in elevation to delineate two zones. There is also another one that seems to start at the border between Greene and Hamblen counties on I 81 in TN.  

[Carvers Gap]

48 minutes ago, BlunderStorm said:

Yep you weren't kidding Carver this run of the NAM

is certified by the Kingsport Snow Hole of Approval... 

Kingsport is like the Chattanooga of this latitude.  We get more snow because of our position in relation to the Atlantic and we are just close enough to get upslope snow.  It also gets much colder up here than compared to southern areas of the forum.  But where we are in the Valley provides exponential opportunities for lesser amounts - rain/snow shadow city.  We are like a decent mid-major basketball team in a Power 5 conference up here.  We get on a good run from time to time...but the blue bloods usually win.  There are events where I am only a ten minute drive from decent snow.  Roan mountain saves the day usually...we drive there when we get whiffed over here.  Takes about an hour, but well worth it.  Plus, when I get home I don't have to shovel.

[Olhausen]

Here's the latest discussion for northern middle Tennessee.

 

Edit: No discussion but rather a winter weather advisory.

 

 

I'm rooting for all the eastern Tennessee people as I know you've been shafted pretty good this year. Good luck!!

 

 

Sent from my iPad using Tapatalk

 

[BlunderStorm]

This probably falls more into the realm of observations but in my favor rain has been on and off all morning and past noon in a nearly stationary area of showers. It has been keeping the temperatures in the low 50s as opposed to the upper 50s I'm forecast for. Here are the obs from the near by airport though it is 550ft higher. https://www.wrh.noaa.gov/zoa/getobext.php?sid=KJFZ

[John1122]

It's hanging out at 48 so far here this afternoon. I wish I was at 2700 feet instead of 1700. There's some land for sale at 2900 feet here that would probably double my yearly snowfall but building a house and moving to chase snow isn't something the rest of the family is quite on board with yet.

[Carvers Gap]

Looking at snow on RadarScope just west of Nashville.  You all seeing any out that way?

[John1122]

Temp has fallen to 43 degrees, stiff northwest wind. Not checked the temp at Clarksville, but snow appears to have started there. 

[Carvers Gap]

1 minute ago, John1122 said:

Temp has fallen to 43 degrees, stiff northwest wind. Not checked the temp at Clarksville, but snow appears to have started there. 

That could be really good for you all.  

[Holston_River_Rambler]

 When I can get Wunderground's wundermap to not act up, the temp graphs for weather stations are showing temps dropping pretty steadily after the front comes through. Looks like the front is just dropping of the plateau as of now.  

[Carvers Gap]

Looks like lightning has been observed at KTRI and Middlesboro.  Crossville is sitting at 41.

[Holston_River_Rambler]

This upper low is already creating some nice instability. The clouds parted and the sun just came out for a bit here in Knoxville and I was able to get what looks to me like a thunderstorm cloud building up! This is looking WNW toward where the front is coming in from. 

[Carvers Gap]

Pretty wintry looking forecast period for mid-late March.  KTRI...

[BlunderStorm]

As of now for 6:16 PM it is 49 degrees it's looking like it's going to be a long messy change over fittingly over me and far NETN like last week between two areas of significantly cooler air. Still the front has not passed so I'm unsure how much of a drop I'll see. Thus far I've pulled victory from the clutches of defeat multiple times this winter season so it is looking great. Being young I'm almost always for snow and this is no different so it is time to get on board of this winter threat for what is likely the last go around for me and the rest of you all. If you're north of I-40, on the plateau, or feeling lucky come on aboard! UPDATE: 7:05 PM Now it's 45.

[Olhausen]

52 minutes ago, Carvers Gap said:

Looking at snow on RadarScope just west of Nashville.  You all seeing any out that way?

It started snowing at 4:30 and heavy at times but the temp is only 34 so no accumulation. I'm right on the edge of the winter weather advisory so it'll be a close call on weather I get any accumulation tonight. Either way just seeing heavy snow fall from the sky is a huge victory this time of year.

[Carvers Gap]

21 minutes ago, Olhausen said:

It started snowing at 4:30 and heavy at times but the temp is only 34 so no accumulation. I'm right on the edge of the winter weather advisory so it'll be a close call on weather I get any accumulation tonight. Either way just seeing heavy snow fall from the sky is a huge victory this time of year.

Awesome!  Anytime we can get snow falling at this elevation on March 20...bonus!  

[Holston_River_Rambler]

Interested to see if Blunderstorm gets any thunder with the precip moving that way. Very dynamic lift developing over NE TN and  SW VA as evident on GOES 16 watervapor over the last two to three hours.  May not be enough to cool the column enough for snow for his area, but still would be nice to see if some of that mid level dynamism is reflected on the ground. 

[bearman]

I have lived in West Knoxville all my 56 years and I would be very surprised if, even in the lower elevations,  snow does not fall on and off late tonight and most a of tomorrow.  Their should be some heavy bursts that whitens the ground at times.  Hear is hoping for a surprise that brings us more, then bring on Spring!

[1234snow]

Areas from Wytheville to Blacksburg have turned over to heavy snow just now.

[Holston_River_Rambler]

VA TECH webcam so we can live vicariously until everything changes over: https://vtnews.vt.edu/webcams/burruss.html 

Also, Le Conte apparently changed over at 6 PM

LATE EDIT: Image of VA TECH and radar added for future reference for the band that moved through. I'd say at least an inch in under an hour. Reports  in the SE subformum of Thundersnow just northeast in Salem, VA

 

 

[BlunderStorm]

Meanwhile 70 miles west snow is only falling at 4,500ft on the peak of Beartown Mountain just to my south and the Grayson Highlands according to the radar. It really shows the discrepancy and sharp gradient in temperatures to the east. Currently it is 44F with no rumbles of thunder to report. Of course it is expected and spirits are up at least over here.

[jaxjagman]

33 here with snowflakes flying around,nothing big hope we can get a good cell to at least put down another dusting