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March 11th-13th Winter Weather Event. Winter's last gasp?


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4 minutes ago, Shocker0 said:

What's up with the very light amounts straight through Crossville and even north to Oneida on some models? Warm nose from hell? GFS shows nothing for central and south Cumberland but shows 5" on the far east and west parts of the county.

Looks like the 12z GFS saw a warm nose at 700 mb for some reason in the Cumberland county area:

0LyrgZn.png

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1 hour ago, Shocker0 said:

What's up with the very light amounts straight through Crossville and even north to Oneida on some models? Warm nose from hell? GFS shows nothing for central and south Cumberland but shows 5" on the far east and west parts of the county.

Heavy sleet mid-Plateau.  I think modeling is having a bear trying to figure out where to place the deformation bands.  I have seen modeling banking a band of sleet against the Plateau on recent runs.  I am trying to figure that out.  I have kicked around maybe a slight downsloping effect with surface winds.  

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3 minutes ago, Silas Lang said:

Yeah, I am not really understanding how Knoxville is escaping the warm nose while the Plateau gets a ton of sleet. Has that even happened before? Just usually seems mixing is more elevation dependent. 

Surprisingly I think it has a couple times over the past few years. I believe during our ice storm on the Plateau in 2015, Knoxville and East Tennessee mostly received snow. But yeah, I'm hoping it's not a sleet storm here the way it's starting to look on the models.

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22 minutes ago, Holston_River_Rambler said:

pretty different profile around Knoxville:

Qxp98XE.png

 

More tapered, sort of a warm cheek. I have no idea if those soundings are realistic. 

I'm terrible at deciphering these things.  Would that indicate the typical "cold rain" scenario with some sleet mixed in?

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1 hour ago, Carvers Gap said:

TRI's issue, if the LR NAM is correct(massive IF), we may be too close to the slp.  Been that way all winter.  Let's see though.  I suspect some in TRI work their way into some snow if the storm verifies.

Yeah, the model's will follow that pattern somewhat as that was ingested from this Winter's track's.

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12z GEFS for comparison 12z -> left.....6z -> right

Note the cluster of lows is back to being over Upstate-ish SC and not over the eastern slopes of the Smokies.  Good trend if you live in E TN, ie would imply less warm nose.

Screen_Shot_2022-03-09_at_11.52.54_AM.pn

 

The 12z GEFS is trying its best to get a clean pass.  It is strung out a bit more as the snow totals are lower due to that.  At first glance, I was like, this is trending closer to MBY.  Really, I think what this implies is there is less energy transfer to the coastal plain.  The SLP simply stays as one and slide up through central NC.

Screen_Shot_2022-03-09_at_11.54.26_AM.pn

 

Of note, a tertiary slp forms at the base of the departing storm.  That cluster has crept a bit closer to the coast.  It is probably too late in the process for that to have meaningful impacts here, but keep an eye on that.  

Screen_Shot_2022-03-09_at_11.55.16_AM.pn
 

 

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One further note and just to beat a dead horse... Notice the cold(orange) is moving a bit quicker.  Also notice the location of the genesis of the slp.  That is pretty much textbook for winter storms in E TN.  I make no promises as far as snow, but that is a great location.  Also, notice less of a warm-nose into TN.  Good trends on both the GFS and its GEFS ensemble below.  As @Holston_River_Rambler, that is a jog SE.  It may be just a wobble, but we really couldn't have withstood another jog NW in E TN.  Trends matter at this stage.

Screen_Shot_2022-03-09_at_12.06.13_PM.pn

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Yeah, I am not really understanding how Knoxville is escaping the warm nose while the Plateau gets a ton of sleet. Has that even happened before? Just usually seems mixing is more elevation dependent. 

As @Carvers Gap mentioned before… the closer you are to the rain, the heavier your rates will be. In this case Knoxville is closer to the heavier rates than the plateau. We won’t see much dynamic cooling in this event but with heavy rates comes some atmospheric cooling from the top down and it’s likely this is beating back the warm layer (which is probably very shallow). Another possibility is we have seen before with a NW wind, the valley can “trap” cold air all the way up to the lower mid levels in a perfect setup.


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Surprisingly I think it has a couple times over the past few years. I believe during our ice storm on the Plateau in 2015, Knoxville and East Tennessee mostly received snow. But yeah, I'm hoping it's not a sleet storm here the way it's starting to look on the models.

This is correct. In this storm the western side of the apps had major downsloping issues but for whatever reason, they didn’t make it west of the mountain counties. The valley NW of 75/40 and west of 81 had a CAD type situation. I’m just north of Knoxville and I stayed all snow and never made it out of the 20’s. At the same time Gatlinburg was in the mid 40’s with rain. I’ve actually wondered if there could have been a weak inverted trough up the valley which negated the downsloping and also added more lift in the valley to help keep the column cold.


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