2/19-2/20 Miller A Magic?

[Daniel Boone]

1 hour ago, fountainguy97 said:

Yeah that's the only player we can get anything of note from at this point for E and NE regions. The initial precip shield is doomed to the transfer. Maybe a very lucky few get 1-2" Wednesday morning at best. 

Spoke with MRX earlier and that along with downsloping is their Concern. They're thinking Northern section's of the Valley and the Plateau will get at least 1-3 with possibly more(basically conservative approach) but, area's closer to the Smokie's not much while the Smokies do well. Of course, this was based on overnight and morning run's undoubtedly.

[Holston_River_Rambler]

Euro upped .qpf a tick again at 12z. Looked RGEMish. 

[PowellVolz]

One thing that’s not going to make forecasting this easy is this system potentially has a very low floor and a high ceiling depending on different variables that can’t really be pinpointed now. GOM convection could play a major role in return flow. 

[Math/Met]

1 hour ago, Daniel Boone said:

Spoke with MRX earlier and that along with downsloping is their Concern. They're thinking Northern section's of the Valley and the Plateau will get at least 1-3 with possibly more(basically conservative approach) but, area's closer to the Smokie's not much while the Smokies do well. Of course, this was based on overnight and morning run's undoubtedly.

Downslope is always a concern with southerly flow at 850mb, but I'm actually becoming less concerned about that as we get closer to the event. The southerly flow at 850mb is pretty weak. 925mb winds are northeast over NE TN. The surface wind is down valley with a bit of an inverted trough along the mountains. In my opinion, this could minimize downslope potential. With limited moisture to work with, we need to limit any downslope in those areas.

[Carvers Gap]

Nice improvement by the 12z Euro.  

[Daniel Boone]

27 minutes ago, Math/Met said:

Downslope is always a concern with southerly flow at 850mb, but I'm actually becoming less concerned about that as we get closer to the event. The southerly flow at 850mb is pretty weak. 925mb winds are northeast over NE TN. The surface wind is down valley with a bit of an inverted trough along the mountains. In my opinion, this could be minimize downslope potential. With limited moisture to work with, we need to limit any downslope in those areas.

Yeah, that makes sense. Probably the Transfer the biggest concern although, the heavier area from the incoming System does appear to be shifting South some and may hit the area fairly good before a Transfer.

[Carvers Gap]

I don't know if this helps, but when I walked out this morning, the top layer of ground was frozen pretty solid.  I saw ice crystals growing in the mulch.  With the very cold winds today, cold temps tonight, and chilly day tomorrow, I think snow could accumulate decently if rates are good(not great but good).  If ground temps were crazy warm, there would have been no dusting of snow in JC this morning.  We had snow on some of our rooftops here.   It looked like it was pouring snow at higher elevations.

[Wurbus]

Just took a look at the SREF's and ,unsurprisingly, it appears the greater valley has mixing issues. Not 100% sure it will happen, but it does happen as energy transfers around here quite a bit.

[ShawnEastTN]

Didn't the Euro have the system in January pretty anemic until just before go time? Am I remembering that wrong? Seems it was on the lower end of qpf and then started bumping QPF run after run up until go time. Maybe I'm mixing it up in my head with another storm. Though it was similar if I remember where GFS was more juiced and Euro less and the euro basically came around towards the GFS.

[PowellVolz]

Nashville just pulled the trigger on WS warning and filled in everyone else with an advisory 

[PowellVolz]

1 minute ago, ShawnEastTN said:

Didn't the Euro have the system in January pretty anemic until just before go time? Am I remembering that wrong? Seems it was on the lower end of qpf and then started bumping QPF run after run up until go time. Maybe I'm mixing it up in my head with another storm. Though it was similar if I remember where GFS was more juiced and Euro less.

Yes and no if I remember correctly…. The Euro was the first mod to start showing qpf issues while most of the other mods were not. Then the other mods and the Euro kinda met in the middle 24 hours or so out if I’m remembering correctly 

[John1122]

MRX goes with a WWA north of 40 and basically west of 81.  Surprised they sent it up this early and surprised it's only an advisory in my area after model trends from today beefed up totals on the N. Plateau to 3-4 inches in less than 12 hours.

[Holston_River_Rambler]

Key parts of their rationale for accums:

If this precipitation moves
in earlier in the morning we`ll likely see more accumulating snow
before sunrise, but if it holds off even just a couple of hours and
doesn`t start to precipitate in the southern Appalachians until
after sunrise, then chances for accumulating snow really decreases.

Once the sun comes up and starts to impact the cloud layer history
indicates that snow occurring during the daytime, in the later parts
of winter with the higher sun angle, and when temperatures are
around or just above freezing... It can lead to much slower snow
accumulations. In addition there could possibly be some downsloping
flow which warms up the atmosphere and eats into the QPF totals.
With temperatures expected to slowly climb through the day to above
freezing for most of the Valley locations any precipitation that
lasts into the afternoon hours will have a decent chance of flipping
over to cold rain, which would also help wash away some of the snow
that might have accumulated earlier in the day. At this time the
most likely scenario is to see advisory level snowfall for much of
the Valley locations, with the lowest amounts in the south and along
the foothills of the Appalachians. We could see 4+ inches in the
higher elevations of the northern Cumberland Plateau and over into
far southwest Virginia on Wednesday as they`ll have the  snow begin
the earliest and the coldest temperatures throughout the day.

[John1122]

I'm not sure where MRX is seeing all the warmth they are. I don't get above 28 degrees on any modeling on Wednesday. The Euro has me at 20f at 1pm.

[Carvers Gap]

The 18z RGEM just ran.  Good chance the mountains eventually are upgraded to WSW or WWA.   MRX is either not including the upslope event which follows or doesn’t believe it will happen.   February systems tend to have a bit more juice.  Time will tell.

[PowellVolz]

29 minutes ago, John1122 said:

I'm not sure where MRX is seeing all the warmth they are. I don't get above 28 degrees on any modeling on Wednesday. The Euro has me at 20f at 1pm.

I’m also not agreeing with the issues of the sun in the morning thoughts. I agree it is part of the big picture but them acting like an hour or two onset delay is going to have major implications on the final accumulations is a head scratcher IMO. I don’t see the sun cutting into snow totals first thing in the morning with a low of 25 degrees in Knoxville, a solid cloud deck and snow falling. It hasn’t gotten above 38 degrees since yesterday afternoon, a low of 26 last night and the temps staying about the same until Wednesday morning should aid in snow accumulations IMO. 

[tnweathernut]

IMO, classic case of MRX overthinking things and trying to be too cute. They don't really even have to go out on that limb right now, so why do it?  Just go with a general 1-3" and fine tune it tomorrow morning.  Getting into this fine of detail 48 hours in advance of a .1-.3 QPF system is silly and drives me nuts.

[tnweathernut]

The timing is more important than anything else.  Because of the cold, why not focus mainly on that.  An early morning start for east and northeast TN will have an impact on travel and schools.  That, more than amounts should be the concern.  Focus on timing.  It will be cold enough for problems, that much we know.

[Daniel Boone]

1 hour ago, John1122 said:

MRX goes with a WWA north of 40 and basically west of 81.  Surprised they sent it up this early and surprised it's only an advisory in my area after model trends from today beefed up totals on the N. Plateau to 3-4 inches in less than 12 hours.

If I were them i'd go with winter weather advisory for now but, also add a winter storm watch. In the discussion I would explain the reasoning. My gut tells me they will upgrade to a winter storm watch in the morning for the northern plateau and SWVA.

[John1122]

I'm also just mystified by the sun angle talk. That's more a thing for March events when it's snowing and 35. Mid February is prime snow climatology for Tennessee/Kentucky/Virginia. 

[Daniel Boone]

2 hours ago, Wurbus said:

Just took a look at the SREF's and ,unsurprisingly, it appears the greater valley has mixing issues. Not 100% sure it will happen, but it does happen as energy transfers around here quite a bit.

The problem is, the Model tends to go straight to mixing or Rain when projecting a Temp above 32 at Ground level. We all know, even if the Temp goes above 32 that if it's below that 200 ft up it's still going to be Snow particularly if the air is not 100% saturated or the gl temp is greater than 35. Even with that threshold if the flakes are big enough it would still be considered wet snow. Radar is faulty itr also as it can be pouring snow but if the Temp is estimated to be 32 or greater it'll show Rain or mix, depending on which radar used.

[Hillbilly]

1 hour ago, Holston_River_Rambler said:

Key parts of their rationale for accums:

If this precipitation moves
in earlier in the morning we`ll likely see more accumulating snow
before sunrise, but if it holds off even just a couple of hours and
doesn`t start to precipitate in the southern Appalachians until
after sunrise, then chances for accumulating snow really decreases.

Once the sun comes up and starts to impact the cloud layer history
indicates that snow occurring during the daytime, in the later parts
of winter with the higher sun angle, and when temperatures are
around or just above freezing... It can lead to much slower snow
accumulations. In addition there could possibly be some downsloping
flow which warms up the atmosphere and eats into the QPF totals.
With temperatures expected to slowly climb through the day to above
freezing for most of the Valley locations any precipitation that
lasts into the afternoon hours will have a decent chance of flipping
over to cold rain, which would also help wash away some of the snow
that might have accumulated earlier in the day. At this time the
most likely scenario is to see advisory level snowfall for much of
the Valley locations, with the lowest amounts in the south and along
the foothills of the Appalachians. We could see 4+ inches in the
higher elevations of the northern Cumberland Plateau and over into
far southwest Virginia on Wednesday as they`ll have the  snow begin
the earliest and the coldest temperatures throughout the day.

One thing missing from the MRX discussion—and a pet peeve of mine—is the lack of consideration for when the forecast is wrong. What if sun angles have less impact than expected? Roads could become covered and dangerous quickly and school systems often treat forecasts as certain for making decisions, when in reality, there should be more risk aversion for public safety. Warnings and advisories aren’t just about forecast accuracy—they’re about giving the public the right information to prepare and too many people don't take it seriously unless they are under an advisory or warning.

[Vol4Life]

There’s still plenty of time for MRX to issue an advisory for Knoxville and points south.  And that’s what I think they will eventually do.

[Holston_River_Rambler]

WBIR in house model showing snow starting at my location around 11pm tomorrow night. Wish I knew which model that was. 

[John1122]

28 minutes ago, Holston_River_Rambler said:

WBIR in house model showing snow starting at my location around 11pm tomorrow night. Wish I knew which model that was. 

WVLT had the same thing. Showed my area at 4 inches by 2pm Wednesday with another burst of snow around midnight Thursday. I honestly wouldn't be surprised if it wasn't the GRAF which a lot of TV stations use now. 

[Matthew70]

Off subject but did you all know there is a bill to make it illegal to storm Chase?

[Daniel Boone]

1 hour ago, John1122 said:

WVLT had the same thing. Showed my area at 4 inches by 2pm Wednesday with another burst of snow around midnight Thursday. I honestly wouldn't be surprised if it wasn't the GRAF which a lot of TV stations use now. 

Yeah, if it's showing same solution it's same. I think it is the Graf but not sure. WCYB uses it now I think. WJHL uses a different one. I can't recall what theirs is. From what I understand it's basically a GFS spinoff. Theie Model has Snow starting around 5 A.M. Wednesday. It has it shooting up through Kentucky before sliding SE. Also has it changing to Rain from Knoxville eastward and NE to the Scott/ Lee County line for a short time before changing back. I disagree with that as the Model is probably using the 32 gl rs demarcation. It still spits 3-5" for Lee , Hancock and Grainger Counties and points west.

    

[PowellVolz]

2 hours ago, John1122 said:

I'm also just mystified by the sun angle talk. That's more a thing for March events when it's snowing and 35. Mid February is prime snow climatology for Tennessee/Kentucky/Virginia. 

my exact thoughts…. Almost like they are trying to talk themselves out of predicting snow. Considering their track record…. Im good with the Debbie Downer approach until we see flakes on the ground. 

[PowellVolz]

1 hour ago, Holston_River_Rambler said:

WBIR in house model showing snow starting at my location around 11pm tomorrow night. Wish I knew which model that was. 

I believe they use something similar to the Columbia SC news station that I’ve posted a couple of times. 

[PowellVolz]

1 hour ago, John1122 said:

WVLT had the same thing. Showed my area at 4 inches by 2pm Wednesday with another burst of snow around midnight Thursday. I honestly wouldn't be surprised if it wasn't the GRAF which a lot of TV stations use now. 

That’s the same one the Columbia station was using.