Jan 16-17th Boom or Bust

[Silas Lang]

6 minutes ago, Holston_River_Rambler said:

Clicking on some of the soundings on Pivotal, it looks like some of the precip it is rendering as rain is borderline snow. I clikced on Knoxville on this map:

 

and got this sounding:

 

Looks like it may just be extremely shallow boundary layer warmth and not a warm nose. 

Just curious, does this help explain the difference in modeling snow totals? Like some runs have nothing while the last GFS was pretty good. 

I know there is a lot going on with this storm and the low placement, but just curious if some models are interpreting rain as snow and vice versa. 

[Holston_River_Rambler]

I've been trying to see what the pivotal soundings say at TRI, but it pivotal apparently thinks I want a severe sounding instead of a winter sounding for that area. I tried to click a normally good down sloping area like N. Sevier or Greene county and it still says snow, even though the model shows rain, but where it shows snow in N. Grainger or Hancock county, the sounding guesses rain as the precip, lol. 

[ShawnEastTN]

Clicking on some of the soundings on Pivotal, it looks like some of the precip it is rendering as rain is borderline snow. I clikced on Knoxville on this map:

 
and got this sounding:

 
Looks like it may just be extremely shallow boundary layer warmth and not a warm nose. 

I have seen those temp differences in previous downsloping storms, where I'm at or below freezing on the Roane/Meigs line and go east toward the mountains and Maryville is close to 40 degrees. That explains a lot of models showing a strip of higher totals from McMinn and NNW with a sharp cutoff east towards the mountains.

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[Holston_River_Rambler]

10 minutes ago, Silas Lang said:

Just curious, does this help explain the difference in modeling snow totals? Like some runs have nothing while the last GFS was pretty good. 

I know there is a lot going on with this storm and the low placement, but just curious if some models are interpreting rain as snow and vice versa. 

IMO, based on the soundings, the hi res models really think we will suffer from insolation and downsloping tomorrow. It could be right, but based on what the soundings show, I would guess precip type will be rate dependent. I have a hard time believing that there won't be snow if we get good rates and are in the deformation zone and there's not really much of a warm nose. Here is a 12z RGEM sounding from just north of Chatt:

 

 

If there's a warm 850 or 925 layer, it can rain even below freezing, but when temps are dropping with height, it just seems snow is more likely. We do live in the valley though, so if anything can go wrong.... 

[Holston_River_Rambler]

And it is snowing again up here in MoCo. Very wet snow, lol. 

[Holston_River_Rambler]

Here's an experiment. Here is what the RGEM sounding has for me right now:

 

That ain't bad. Neighborhood weather station is at 38 and we have snow falling. I mean, light snow and maybe some rain mix. If we had some good rates I think the boundary layer would dynamically cool.  

[Carvers Gap]

12z GFS continues the trend of bumping up totals in E TN - Chattanooga...Wow!!!

[TellicoWx]

@Holston_River_Rambler...here's the Xsec at TYS from the 12z RGEM and 3k NAM...trend the last 4 runs has to been slowly erode the finger quicker. At Lovell, the finger is almost completely gone, which is what is jumping the totals over the southern valley on some models

[WinterWonderland]

23 minutes ago, TellicoWx said:

@Holston_River_Rambler...here's the Xsec at TYS from the 12z RGEM and 3k NAM...trend the last 4 runs has to been slowly erode the finger quicker. At Lovell, the finger is almost completely gone, which is what is jumping the totals over the southern valley on some models

So we're not getting  the "finger" as bad as we were?  

[Weathertree2]

5 minutes ago, WinterWonderland said:

So we're not getting  the "finger" as bad as we were?  

Perhaps depends what model you choose.

[John1122]

Snow showers this morning at 35 degrees. 8-13 inches here across most modeling as the event is imminent. What could possibly go wrong? 

[Daniel Boone]

I think ur golden there man.

[John1122]

2 minutes ago, Daniel Boone said:

I think ur golden there man.

MRX lowered my chance of > than 4 inches from 70+ percent to 40ish percent from last night into today. They seem convinced models aren't right here. 

[bearman]

Looks like lookout has some snow at the moment.

[Daniel Boone]

Just now, John1122 said:

MRX lowered my chance of > than 4 inches from 70+ percent to 40ish percent from last night into today. They seem convinced models aren't right here. 

They're going from early morning runs and as we all know, their own opinions and biasis.

      I can see the caution within the great Valley but, not there.

[ShawnEastTN]

Looks like lookout has some snow at the moment.

Don't tell MRX this, or any reports from John or Holston. They'll say it's just solidified rain.

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[Uncle Nasty]

Just finished my weekly Costco run an hour ago. Our Costco is over the state line into Georgia. All the main roads in N. Georgia have a heavy layer of brine. I know they are thinking ahead but it will all be washed away by the rain, even if we get any frozen precip later. Probably between 1/2"-1" of rain. I don't see how the brine will have any impacts on the roads in the event of frozen slop.

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[TellicoWx]

Think the models are really struggling with the thermals, especially the southern valley. If you follow the path of the cold core as it swings thru Central MS/AL, its like they don't know how to handle it column wise once it reaches the TN/GA/NC border....hence the range is still T-10" lol. 

[Met1985]

Good luck fellas on this side of the mountain!

[bearman]

Peachtree just put 2 northwest Ga counties under a winter storm warning for tonight and sunday morning.  I supose they are on the plateau?

[TellicoWx]

10 minutes ago, John1122 said:

MRX lowered my chance of > than 4 inches from 70+ percent to 40ish percent from last night into today. They seem convinced models aren't right here. 

I think you are golden..add in the clipper system trailing right on the heels 

[ShawnEastTN]

I honestly think MRX should at least issue WWA for Knox, Loudon south. So much modeling showing that area getting potentially plastered with heavy snow potentially warning criteria snow. The only reason they don't is climatology suggests that shouldn't be the case but it wouldn't be the first time the western great valley and southern great valley score in a scenario like this.

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[TellicoWx]

3 minutes ago, ShawnEastTN said:

I honestly think MRX should at least issue WWA for Knox, Loudon south. So much modeling showing that area getting potentially plastered with heavy snow potentially warning criteria snow. The only reason they don't is climatology suggests that shouldn't be the case but it wouldn't be the first time the western great valley and southern great valley score in a scenario like this.

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Unless the NBM changes drastically (too much model spread still I think), very doubtful they will

[Daniel Boone]

1 minute ago, ShawnEastTN said:

I honestly think MRX should at least issue WWA for Knox, Loudon south. So much modeling showing that area getting potentially plastered with heavy snow potentially warning criteria snow. The only reason they don't is climatology suggests that shouldn't be the case but it wouldn't be the first time for sure the western great valley and southern great valley score in a scenario like this.

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Agree...better to alert than not even if it went the no show snow way. I think they are doing as u say and also afraid of crying wolf. 

     

[Uncle Nasty]

Sort of surprised in my current location. Just on the state line into Georgia just leaving from visiting my mom to head back to Ooltewah. It's 39° and a very light rain with some sleet pellets mixed in bouncing off the car. Originally our rain wasn't scheduled until very late afternoon.

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[TellicoWx]

Dug more into the NBM..its running hourly but cant download the grib files unless you have the credentials. This system is a big test for it, uses the current conditions to reanalyze pretty much all the models solutions for the current time frame, then corrects the known bias that is being shown and applies that to the blending for each hourly update.

[ShawnEastTN]

Dug more into the NBM..its running hourly but cant download the grib files unless you have the credentials. This system is a big test for it, uses the current conditions to reanalyze pretty much all the models solutions for the current time frame, then corrects the known bias that is being shown and applies that to the blending for each hourly update.

Yeah I don't have access to NBM.

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[TellicoWx]

So basically it's auto correcting each model with every passing hour and spitting out the final total solution

[PowellVolz]

I have this feeling I’m going to do well if temps are not an issue. To my knowledge, downsloping has never been an issue NW of 40. When we get those spring mountain wave events, it’s nothing for Sevierville to be 10-15° warmer than me.


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[PowellVolz]

Dug more into the NBM..its running hourly but cant download the grib files unless you have the credentials. This system is a big test for it, uses the current conditions to reanalyze pretty much all the models solutions for the current time frame, then corrects the known bias that is being shown and applies that to the blending for each hourly update.

Wow…


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