BlunderStorm

AREA FORECAST DISCUSSION...UPDATED
National Weather Service Morristown TN
1249 AM EST Mon Dec 14 2020

.UPDATE...
FOR 06Z AVIATION.

&&

.DISCUSSION...

Not a whole lot of change to the forecast this evening. Biggest
change was to slightly delay onset of precip across the central
east TN Valley and northeast TN by a few hours. Looking at the
latest data, still a very difficult forecast in terms of snow
potential across the northern Cumberland Plateau and southwest VA.
I think the biggest bust potential is across Wise County and
Russel County VA, our most northern counties in our CWA. By bust
I mean our current snow totals could be too low. However, I just
don`t feel confident enough to raise the current totals that are
in place. To be honest, we probably won`t have a good grasp on
snow totals until we actually see when the changeover occurs. With
this event changeover-time is everything. A changeover from rain
to snow that occurs just an hour or two earlier could raise snow
totals by a few inches and vice versa if changeover is later than
expected. The current SPS and snow totals mentioned within still
look reasonable so will let it ride for now. Will be closely
watching how this event unfolds through the night.

SR

Down to 41. Since the arrival of the rain the temperatures have proceeded to drop steadily at a degree an hour. At this rate however the sun will stagnate the drop and the system will have already mostly concluded. Still, it is movement in the right direction and with any luck the drop in temperature will accelerate. On it's own evaporative cooling may give me another degree. Wetbulb is just under 40 with 94% humidity. All the more puzzling is the wind direction from the southwest from deeper in the valley not keeping the temperature at the very least stable. Furthermore if clouds insulate then why were temperatures stable instead of dropping in the first few hours of the night while the sky was still partially uncovered? Me no understand heat dissipation.

Alright, here we go. Snow? IMBY? Will see, Currently 43 and a long way to drop.

1 minute ago, John1122 said:

The 12z Euro looked like an early December 2009 paste job here that put down 8 inches of heavy wet cement overhead while it rained north, south, east and west of here. For whatever reason this county was just in the perfect spot in the storm and it dropped silver dollars for 5 straight hours. It was mixed slush about 15 miles away in Scott and Whitley County Kentucky but just hammered here. 

Rates will overcome?

I noticed on the latest GFS run the first system that rolls through the midwest is more progressive perhaps introducing less cold to the Tennessee Valley in time for the second system. Another possibility is that with a stronger second system sporting a more defined center of low pressure it acts to warm up the valley without an area of high pressure to the NW reinforcing colder temps. If we were looking at more of a semi Miller A setup like we saw with the Euro last night perhaps it would be manageable for at least the eastern regions but this does not look to be the case with the euro biases and trend as of the 12z run. Instead echoing what Tellico said we may be looking at a weak to marginal slider with potential for snow in high elevations and maybe some lucky areas along I-40 and north. As a side-note the Canadian seems to be in general agreement with the GFS. In the meantime will see what the Euro has to say. On the bright side it would seem we will likely see multiple opportunities as December progresses and the effects of a -NAO and -AO really start to kick in. (fingers crossed)

It's looking like I end at 0.85"(ish) for the event. A few under the radar bursts managed to lay down a nice thin coating.

I know it's currently flurrying in downtown Nashville. https://www.webcamtaxi.com/en/usa/tennessee/broadway-nashville.html

Well it would seem barring some really good NW flow tonight out of everyone I have drawn the short end of the stick. Latitude and elevation be damned I got a trace. As for why, I dunno. Perhaps the atmosphere was drier here but I think it's more likely to do with the 2nd wave of energy in this system associated with the upper level low which tracked to my SW. I could be entirely wrong and I'm sure someone here would have a better understanding haha. For those of yall in harsher climos congrats though!

1 minute ago, Stovepipe said:

They bumped the valley up to a half inch.

 

8 hours ago I would have agreed with their original call. I'm glad there were willing to let up in light of this systems overperformance.

It is now steadily snowing at a moderate clip and temperatures are just barely hovering above freezing at 33. Snow has not began to accumulate on the grass however as of yet.

Just now, John1122 said:

The radar can see the lower atmosphere better the closer precipitation is to it. Snow, especially when it gets the NW flow component, comes from lower in the atmosphere. The Plateau is about as far away from each radar site in the area as possible. Especially Jamestown, and the radar beams can basically shoot over the snow at times on the edge of its range. 

Clinch mountain for example to the north of MRX has a tendency to do that I believe.

At last I can now say snow is lightly falling! Currently 34F.

2 minutes ago, BhamParker said:

18z 3K NAM looked amazing for the mountains. Shows some pretty heavy stuff for 8-10 hours. It has really gotten cold with the snow falling!

As a general rule that model tends to exaggerate orographic dependent snow accumulations. Still it can be really fun to look at.

Kingsport/Gate City seeing any action yet?

1 minute ago, fountainguy97 said:

On the cusp here. 36 surface with a tiny warm layer left.  

 

Sky across the valley is heavy and white with peaks above 3k in the clouds.  Feels like snow

Upstream radar is looking so good. I am pumped.

I feel exactly the same and your description is identical to mine.

Still dry at the NE fringe of the forum region. Down to 36F and the radar presentation is looking really healthy.

Tellico is a beautiful area having visited it during the eclipse.

Just now, ShawnEastTN said:

Had rain graupel/melted snow flake slop a few minutes ago on the Roane/Meigs county line area.

Sent from my SM-G965U using Tapatalk
 

@McMinnWx If he can get some flakes out of this you likely can too.

Just now, BhamParker said:

Tapered off to some lighter flurries at the moment, it was moderate for about 45 minutes but none of it accumulated. Looks like the good stuff will be this afternoon and into the night time hours for sure. Sure is nice seeing some flakes!

Good to hear, getting anything to stick in November is hard to pull off anyway. I'd consider it an appetizer.

8 minutes ago, PowellVolz said:

Snow reports down to the Alabama boarder assuming it’s not fake news.

It's reported along the southern plateau I buy it. Area around Sewanee and Monteagle is just under 2000'

I wonder if any flakes are making it down under that light developing band over Nashville...

Now down to 41F with a DP of 39. Was in and continue to be in the "dry pocket" (still some drizzle) but that much was a given thus far due to my location relative to the systems setup. Progression towards freezing is likely to accelerate as the front passes in the next hour. NWS is calling for an inch with models showing about 2 inches.

Currently 45F at 2100', will see how quickly the temps drop. Not extremely substantive but hey I'm here!

For the record yes it is flurrying! Currently 34!

Looks like this is likely to be the biggest snowfall this season the way it's going here. Quite impressive