Dandridge Dollop 12/24/20 Storm Thread (Winter Wonderland)

[Blue Ridge]

Just now, Icy Hot said:

When did WSW criteria change? I thought it was 6" or more for our area?

From https://www.weather.gov/mrx/watchwarnadv:

[TellicoWx]

16 minutes ago, Icy Hot said:

When did WSW criteria change? I thought it was 6" or more for our area? They are calling for 2-4??? This is straight from NOAA.GOV - A Winter Storm Warning indicates that heavy snow of at least 6 inches in 12 hours, or at least 8 inches in 24 hours, is expected. It can also be issued if sleet accumulation will be at least half an inch. 

Can differ from office to office on criteria...I know FFC is real low

[Carvers Gap]

52 minutes ago, Math/Met said:

Looking at the soundings after the initial band moves through, the 3km NAM soundings are extremely impressive over NE TN on the lingering snow. Snow growth layer drops very low, so terrain induced lift extends into DGZ. Very steep lapse rates extend through the DGZ (SFC CAPE of over 50 in some areas). This all suggests potential convective snow bands and very high snow ratio on the lingering snow by 03z and beyond.  Probably 20:1 or better ratios after 03z with some of those snow bands. Those are always some of my favorite things to watch.

Yeah, that is pretty much an awesome post right there.

[RawCrabMeat]

38 minutes ago, Blue Ridge said:

Santa came early...

Edit to add: Map hasn't yet updated. Looks like they upgraded watch to warning and SPS to WWA except the furthest SW counties (incl. Hamilton). 

Edit 2: To recap: WSW for 2-4", locally higher depending on elevation; WWA for 1-3"; SPS remains for minimal accumulations and hazardous travel.

Edit 3: Map just updated. 

1-3 here with WWA already is actually surprising from mrx 

[Wintersnow888]

Could someone explain why it seems the Nashville wx office ( which is the one that issues for us in Cumberland county, not sure why we aren't under Morristown?) always is the last one to post any wsw/ or watches , and they are always a lot more cautious. They usually end up boosting the totals at the very last minute if ever, which makes them wrong alot IMBY . This time it's gone from getting maybe 3-4 down to an inch now .....ugh. I know it's hard to predict for the plateau, but sometimes I can get a better forecast from Morristown. I'm kinda new to posting but really learn a bunch from the other members, thanks! I'm about 10 mi NW of Crossville and several hundred feet higher in Cumberland county close to the Putnam county line

[McMinnWx]

Looks like we aren’t getting much of anything.  Good luck to everyone is, especially those of you in the northeast!

[Daniel Boone]

2 hours ago, Holston_River_Rambler said:

12z Euro:

 

 

Big ole 11 inch lollipop for Wise. High Knob and Black Mountain over a foot !

[Carvers Gap]

18k NAM on board for NE TN.  3K NAM is going nuts - worth a look if you live from Knoxville or eastward.  

 

[Kasper]

Well I’m going to hit the bottle tonight, tracking storms has me looking for the Vodka

[John1122]

Rgem maintains its stance of much more widespread snow vs the far east NAM camp. HRRR has random convective bands that drop 2-4 inch strips if you happen to get one. 

[Holston_River_Rambler]

42 minutes ago, Carvers Gap said:

 3K NAM is going nuts

**For Entertainment Purposes Only**

 

It really likes the Mt Rogers area/ Grayson Highlands area

[Holston_River_Rambler]

Def a fan of the RGEM for my area. Everything else is too little too late for most of MoCo:

 

Really interested to see if something like those convective bands verify under the lapse rates of the upper low. 

[John1122]

As a rule you can cut the 3k extreme totals by about 60-75 percent. I believe in the last event it showed LeConte with maybe 24 inches and I think they got 6 or 8.

[ShawnEastTN]

Def a fan of the RGEM for my area. Everything else is too little too late for most of MoCo:

 
Really interested to see if something like those convective bands verify under the lapse rates of the upper low. 

One of those bands would be awesome!!! 15:1 or 20:1 ratio with pouring snow... Just a dream to get one of those imby.

Sent from my SM-G965U using Tapatalk

[John1122]

1 hour ago, Wintersnow888 said:

Could someone explain why it seems the Nashville wx office ( which is the one that issues for us in Cumberland county, not sure why we aren't under Morristown?) always is the last one to post any wsw/ or watches , and they are always a lot more cautious. They usually end up boosting the totals at the very last minute if ever, which makes them wrong alot IMBY . This time it's gone from getting maybe 3-4 down to an inch now .....ugh. I know it's hard to predict for the plateau, but sometimes I can get a better forecast from Morristown. I'm kinda new to posting but really learn a bunch from the other members, thanks! I'm about 10 mi NW of Crossville and several hundred feet higher in Cumberland county close to the Putnam county line

Nashville being in CST almost always is a little later than MRX with disco/storm products.

[TellicoWx]

19 minutes ago, John1122 said:

As a rule you can cut the 3k extreme totals by about 60-75 percent. I believe in the last event it showed LeConte with maybe 24 inches and I think they got 6 or 8.

Wow, LaConte only got 6-8"? Recorded over a foot on the Skyway here. But, yeah it's usually about 25-30% below what the 3k shows on the peak here.

[John1122]

Quote

In fact, could be some pretty intense snow shower activity at
times as lapse rates steepen up through the dendritic growth zone.
Temperatures by Christmas morning should dip into the teens.

Snow showers will taper
off into early Christmas morning; however, a secondary vorticity
lobe looks to swing through on Christmas Day, helping to reinforce
the clouds and some snow shower activity

JKL disco about the snow showers that follow the frontal precip Thursday night and Christmas day energy.

[John1122]

3 minutes ago, TellicoWx said:

Wow, LaConte only got 6-8"? Recorded over a foot on the Skyway here. But, yeah it's usually about 25-30% below what the 3k shows on the peak here.

After looking at the next day's post on high on LeConte, they ended up with 11 inches. So slightly less than 50 percent of what the 3k was showing. It really keys on higher terrain and just dumps snow on those spots for some reason.

[ShawnEastTN]

I guess with the front now bisecting Arkansas approaching the Mississippi River this really is going to rapidly move into nowcast obs mode. We going to continue on this thread or someone opening an obs thread?

 

Edit to add: speaking of which 20 degree difference between southern AR and NW AR.

 

Sent from my SM-G965U using Tapatalk

 

 

 

 

 

 

[TellicoWx]

I know, I know..it's the HRRR in la la land (end of it's run)..but something interesting. As the center of the trough passes by, there is an enhancement of snow over the valley. Something to watch for on the other short range modeling. With the way everything is modeled, and such a vigorous trough (evident by the numerous banding features on all short range models), while the wrap around low moisture is almost locked in, I think there is a "potential" to bust high across the valley back to middle TN on the forcing from the trough itself (wringing out all available moisture/ terrain enhancement for the plateau adding even more lift/ and the high snow ratios shown)....but could be wishful thinking too lol

[ShawnEastTN]

I know, I know..it's the HRRR in la la land (end of it's run)..but something interesting. As the center of the trough passes by, there is an enhancement of snow over the valley. Something to watch for on the other short range modeling. With the way everything is modeled, and such a vigorous trough (evident by the numerous banding features on all short range models), while the wrap around low moisture is almost locked in, I think there is a "potential" to bust high across the valley back to middle TN on the forcing from the trough itself (wringing out all available moisture/ terrain enhancement for the plateau adding even more lift/ and the high snow ratios shown)....but could be wishful thinking too lol

I am of agreement. I think this has high potential to bust higher for central and southern valley, plateau and highland rim.

 

Sent from my SM-G965U using Tapatalk

 

 

 

[Kasper]

13 minutes ago, TellicoWx said:

I know, I know..it's the HRRR in la la land (end of it's run)..but something interesting. As the center of the trough passes by, there is an enhancement of snow over the valley. Something to watch for on the other short range modeling. With the way everything is modeled, and such a vigorous trough (evident by the numerous banding features on all short range models), while the wrap around low moisture is almost locked in, I think there is a "potential" to bust high across the valley back to middle TN on the forcing from the trough itself (wringing out all available moisture/ terrain enhancement for the plateau adding even more lift/ and the high snow ratios shown)....but could be wishful thinking too lol

I’ve had the same thoughts, as vigorous as the front and overall NW flow, I think we Squeeze everything out

[TellicoWx]

From the 18z 3k, another feature that shows how vigorous this trough is...How many times do you see a model producing intense lake effect snow off Lake Wheeler in N. AL?

[John1122]

The RGEM is capturing the likely secondary snow better than the GFS/NAM/Euro. The HRRR is capturing it too. The RGEM has been consistent for two days that snow will linger. These major league Arctic airmasses are able to squeeze everything out, the snow growth zone -15c temps get low in the atmosphere and create the snow that falls that doesn't even show up on the radar because it's falling from so low in the atmosphere. 

[Holston_River_Rambler]

Always like it when the airmass is so cold, you can see it in IR satellite during the day:

 

 

Grays that look like clouds sliding through SE OK, but there are no clouds, just cold:

 

Front is popping some convection now too, over central AR:

 

and speaking of lapse rate snow showers, they look pretty healthy in the upper left of that gif, over KS

 

[ShawnEastTN]

The RGEM is capturing the likely secondary snow better than the GFS/NAM/Euro. The HRRR is capturing it too. The RGEM has been consistent for two days that snow will linger. These major league Arctic airmasses are able to squeeze everything out, the snow growth zone -15c temps get low in the atmosphere and create the snow that falls that doesn't even show up on the radar because it's falling from so low in the atmosphere. 

I trust that aspect of the RGEM as it really dealt well with the trailing energy with the last event also. The NAM had snow out of my area while it was still snowing the RGEM nailed it.

Sent from my SM-G965U using Tapatalk

[1234snow]

Always like it when the airmass is so cold, you can see it in IR satellite during the day:

 
 
Grays that look like clouds sliding through SE OK, but there are no clouds, just cold:
 

Front is popping some convection now too, over central AR:

 
and speaking of lapse rate snow showers, they look pretty healthy in the upper left of that gif, over KS
 

Not sure if this system will fit the definition of a “Blue Norther” for those folks in Texas/Oklahoma but it is certainly dropping due south.

You can really see the orientation of the trough well in those animations.

[BNAwx]

I don’t think here just east of Nashville that we’ll see any anafrontal changeover.  I’m more interested in the energy coming in behind it on Christmas Eve into Christmas morning.  If we get anything, I’d say that’s where it comes from.  Considering how cold it will be, it won’t take much to at least whiten the ground if we can get under a decent band.  

[TellicoWx]

OPRH (measure of potential snowfall rate) sounding over Monroe Co at the time of change over. -2.35, could be some really intense rates right after it changes over.

[Carvers Gap]

18z GFS was putrid as was its ensemble.  6z was similar.  So, 12z seems to be the outlier for that model during the past couple of days.  Wonder if it is its progressive nature?  Other modeling seems to be fairly settled.