Math/Met

43 minutes ago, John1122 said:

18z Euro was similar but less in SEKY for snow through 90 hours. That was the last map I was able to see. . Ratio'd I'd say 3-5 Plateau, 2-4 Central Eastern Valley and Southern Ky, 4-8 in NETN/SWVA.  That said, it's still snowing in most of East Tennessee at 90 on there.

I don’t have access to the 18z, but it looks like it increased precip along the eastern areas. Is that what you see? I haven’t seen snow maps or temperatures, so I’m not sure how that translates to snow accumulation.

Edit: Never mind, I found a snow map.

57 minutes ago, John1122 said:

The Euro doesn't see as much downsloping for the NE so that's good. 

Things could change with the orientation at 850mb, but I’m leaning towards the Euro in terms of the amount of downslope over NE areas.  Usually the Euro does a good job of showing 925mb wind acceleration through the French Broad valley in NC during a downslope situation.  I don’t see much of that with this system looking at hour 72. The 925mb flow isn’t cross barrier for most of the region.  The ESE winds at 850mb would still be a factor but less compared to what the GFS shows.  Small changes could make a big difference in how significant the downslope is, so it’s something to watch for sure.

1 hour ago, Carvers Gap said:

You know I haven't even look at winds with this.  Winds aloft must be humming to produce those solutions.  The Euro is less sensitive to it.  Hopefully it will be a good test as to weather the GFS is a bit too sensitive to it.  It has been such a long time since we have had this type of system, I am going to have to brush up on the bias with these.  @Math/Met, you are the expert on winds in the mountains in Greeneville.  Is the downslope overly pronounced on that run or legit.  I am not sure.

The 850mb winds turn from E to SE at around 96 hours. That’s what the FV3 seems to be depicting in that area. It shows up on the 850mb Vertical Velocity products.

I certainly can’t dismiss that output, but I think it could be overdone.  Based on that track, it’s really not a situation that I would normally worry too much about true downslope winds (when temperatures skyrocket along the foothills). The 925mb winds aren’t orthogonal to the mountains and winds near the surface are from the northeast.  In my opinion the GFS has a tendency to go overboard with downward vertical velocities in that area as well. It tends to paint a bullseye of downward velocities in that exact location. I’ve seen it on several occasions.  I’m not sure if it is correct or not, but I’ve seen unusual VV outputs in that area with southeast winds at that level.

I know that doesn’t answer the question, but that’s about all I can tell you at this point.

15 minutes ago, TellicoWx said:

I'm focusing on that too. The position of the low at 850mb makes a huge difference for parts of East TN. We want the flow over our region to have more of an easterly component and less of a southerly component. For multiple reasons (less WAA, less downslope potential…).

11 minutes ago, John1122 said:

Neighboring WFO in Kentucky, NC and VA have issued winter weather advisories for snow overnight and into tomorrow. Waiting to see if MRX follows suit. Fairly robust wave working through the area over the next 24 hours. Just had a burst pass through that was blinding for about 10 minutes. Hopefully they increase in frequency overnight.

Model soundings show fairly steep low level lapse rates and saturation extending into the snow growth zone tonight. I would expect there to be some decent snow shower activity. Just need to get lucky and be under the right band. 

24 minutes ago, John1122 said:

 I've never been to Camp Creek, do people live there? I can't imagine the shingle replacement costs each year if they do.

Yes, it is a small community at the base of the mountains. The NOAA wind tower is located at Camp Creek School. There is also a Free Will Baptist Children’s Home next to the school. Most homes in that area have a metal roof.

The winds aren’t just a Camp Creek problem. Almost the entire southern half of Greene County is really windy in these situations.  South Greene High School has been damaged several times over the years

Up to 81mph at Camp Creek on the latest update.

90mph recorded at Cove Mountain.

Downslope winds helped to erode the area of precipitation and the mountain wave event has started. Already gusted to 71mph at Camp Creek.

I'll post this in the obs thread since my previous mountain wave post was here. 

MRX issued a Wind Advisory for the mountains of East TN for tomorrow.  The low level jet near the mountains isn't overly strong with this system, but there is still plenty of wind energy available. Model soundings over that area are very favorable for mountain wave development after 15z tomorrow.  I think this has potential to be a moderate mountain wave event for a few areas. 

I just wanted to say that the discussion about the Bays Mountain snow band was really interesting. I’ve always had an interest in the effects of the terrain on our local weather, but I’ve never focused on that particular area before. I think Jeff’s explanation was spot on (as usual).

Someone also mentioned the band that set up in the Cocke County area. That is something I’ve noticed several times during a more westerly wind flow.  It’s probably a combination of convergence and upslope enhancement in that region.  These effects seem to be more significant during really cold air masses, when the dendritic growth zone is closer to the surface and the resulting low level vertical motion extends into the DGZ.

A wind event is underway for parts of East TN. Camp Creek has already gusted to around 63mph, and the 00z Nam has the LLJ strengthening over the next few hours. Even though the 850 mb wind direction is south/southwest, winds closer to the surface are more of a cross barrier flow. 925mb wind direction is typically a better indication of potential downslope winds for this area. This shouldn’t be a major event, but a few hours of strong gusts are possible.

JoMo,

I don’t post here often, but it’s awesome to hear that you made it through the storm. It was apparent that the people on this board truly care, and we are all glad you’re safe.