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Freezing Rain, Sleet, Snow, Rain...Kitchen Sink (12/15-16)

Anyways, this is a storm I think that will do sleet at temps above 36 then snow till 32 then freezing rain as soon as the first lull hits with temps near 30 or below. All ptypes but the colder you get the less snow/sleet because dry air at the surface vanishes with warmer air aloft above the tree line. The Birdman Storm.
 
With the CAD deepening and looking like the high has gotten quite a bit stronger you could definitely see snow in the high elevations extending down into the far northern Piedmont. Think everyone Dow to highway 74 in NC will likely be sleet with some ZR mixed and everyone south of there into the central upstate would like be all ZR.
 
Damn we’re still trending to more confluence and GL ridging ?! Keep doing that and that introduces a quick front end snow potential for the NC Piedmont FA041B50-948E-44B3-8C2C-D05C8289EA06.gif
Even the nam is doing the same in the LR with stronger confluence >>> better GL ridging and better CAD, gonna have a pants bursting run soon ?B2F5C87E-7209-43D9-9DE2-B1EE4EA69918.gif
 
Myfrotho704_ said:
Damn we’re still trending to more confluence and GL ridging ?! Keep doing that and that introduces a quick front end snow potential for the NC Piedmont View attachment 57209
Even the nam is doing the same in the LR with stronger confluence >>> better GL ridging and better CAD, gonna have a pants bursting run soon ?View attachment 57210
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Idk man not trying to be Debbie downer on snow but it's hard to find much evidence for snow in NC. Waa in the mid levels is probably going to be stout with the H85 and H7 flows with such a southerly component. I think the better hope for many is the models are underestimating the depth and intensity of the cold push in the sfc to 925 layer and there is more sleet. I could be wrong especially if we are seeing the models as usual being late on the precip arrival
 
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SD said:
Idk man not trying to be Debbie downer on snow but it's hard to find much evidence for snow in NC. Waa in the mid levels is probably going to be stout with the H85 and H7 flows with such a southerly component. I think the better hope for many is the models are underestimating the depth and intensity of the cold push in the sfc to 925 layer and there is more sleet. I could be wrong especially if we are bc seeing the models as usual being late on the precip arrival
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I’m just saying for the very very front end part of it, the GFS tries to show a window with soundings that could wet bulb quickly, but yeah I agree at this point sleet is a win with this look, stronger CAD is just locking in freezing temps 242CDA87-4C01-48CE-A734-E42F6656BE39.png
 
Realistically if you want snow in NC the better hope is more intense secondary cyclogenesis off of the coast farther south. This would help start stacking the sfc into the mid layers and veer the flow resulting in caa and the ptype changeovers moving toward the S and east. Unfortunately as modeled right now this is a classic ice storm
 
SD said:
Realistically if you want snow in NC the better hope is more intense secondary cyclogenesis off of the coast farther south. This would help start stacking the sfc into the mid layers and veer the flow resulting in caa and the ptype changeovers moving toward the S and east. Unfortunately as modeled right now this is a classic ice storm
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Hopefully sleet can start becoming dominant if we keep trending colder
6FBEC293-D8E0-4542-A053-A3DB347E903E.gifFCF0E371-34CA-4099-808F-02EC80EB249B.gif
 
Myfrotho704_ said:
I’m just saying for the very very front end part of it, the GFS tries to show a window with soundings that could wet bulb quickly, but yeah I agree at this point sleet is a win with this look, stronger CAD is just locking in freezing temps View attachment 57212
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That's not a bad sounding at all. As we know the models often underestimate the intital fgen and upglide and are late on precip arrival. If we get one of those fingers of precip rolling in early it would certainly change things a little and maybe bring a little snow but it would also likely shift the freezing rain/sleet lines SE since it would lock in the CAD dome. This would likely keep the coastal trough at Bay since it would be bumping up against a deeper cold dense airmass and the coastal low farther east
 
I don’t care how many dislikes I get but I see promising trends for less ZR and more mixing esp for a large area (Winston-Statesville-Hickory). Honestly I’m watching for a thread the needle onset all snow if everything comes together for a large chunk of North Carolina. We can get the snow to come off the mountains if trends continue. However, keeping it all snow virtually has no chance with what I’m seeing.
 
As I mentioned yesterday, I find it suspect that this is entirely a snow -> ZR changeover, with little room for sleet. These things most always never verify that way. I would expect, especially if there are colder trends, this to be mostly sleet.
ECE069EA-116A-43F8-92DE-12B933880215.jpeg
 
This is not a favorable event for south western North Carolina. Hardest area to forecast will be near Asheville. Cold rain near.
 
In an ideal world the trailing kicker over the PNW would trend slower, the wave would dig, and the low in the north atlantic would slow and help suppress heights over the eastern us. Don't think it happens but there is room here to continue slowly inching south and coldertrend-ecmwf_full-2020121200-f102.500hv.conus.gif
 
Ollie Williams said:
As I mentioned yesterday, I find it suspect that this is entirely a snow -> ZR changeover, with little room for sleet. These things most always never verify that way. I would expect, especially if there are colder trends, this to be mostly sleet.
View attachment 57218
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Yeah soundings do have that look near Lake norman NC for example 2F70DE1B-E40F-4EC0-86AC-A011D2D19B13.pngF27FF5C5-F077-45FF-B311-4D2C15138199.png
 
ForsythSnow said:
I do see a bit of a trend in North Ga as well for onset ZR becoming possible. It's getting closer each run but I'm not too sure about the ridge strength only being a 1037.
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It’s increasing every run and inching south. These CAD situations always trend colder, stronger, and generally press into NE Georgia at least.
 
ForsythSnow said:
I do see a bit of a trend in North Ga as well for onset ZR becoming possible. It's getting closer each run but I'm not too sure about the ridge strength only being a 1037.
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1037 is very intense for a CAD high, getting close to rivaling Dec 2002 in terms of parent high intensity
 
I hinted at this in a post yesterday, but one of the big things that's going to make it difficult to see a significant period of snow (and also makes trending away from a true Miller B more or less impossible) is that this system will already be starting with a well-defined closed 850 mb circulation (and also 925 as @SD pointed out), which will trek NW of the Appalachians. As long as the flow associated with that low is dominant, we will end up with mainly southerly winds that will create a big ol' warm nose.
850_mb.png
Avoiding this requires one of a few things to happen:

- The 850 mb low needs to weaken; not sure there's been much of a trend for this, but there's still time.
- The 850 mb low needs to shift more south; again, haven't seen much of a trend of this in the last few runs; it was happening yesterday some though.
- The 850 mb low needs to slow down/shift west. This has been happening, and it allows a) the SE Canada trough to provide a dominant flow to advect more cold air ahead of the storm, and b) more time for the secondary low to develop/induce its own flow. That second point is unlikely to actually come into play (transfer is currently modeled as happening around DC-Philly), but it is a possibility. If you look closely, you can already see how the coastal low is changing 850 mb wind vectors in the image above.

What the latest models show for the strength/position of this circulation a day or so before impact:
850mb_low_ahead.gif

I think absolute best case (not expecting it) would be a trend towards a Jan. 2016 type ptype evolution; I got about 3" snow/sleet with a crust of ZR, and would be happy with half of that. Not sure if we're comparable in the precip department though (I seem to remember that storm had very high QPF?).
 
Looking probable if not likely that somewhere in the Piedmont of NC and probably upstate of SC is going to see a major ice storm on Wednesday, whether or not that’s Greensboro, Charlotte, Raleigh-Durham, or Greenville-Spartanburg, &/or all of the above remains to be seen but I think someone is going to get clocked and it might be lights out
 
Spurs up said:
so how can I get this down to Columbia? ?
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High needs to press further south but you are seeing ensemble members that have the northern midlands and northern suburbs in on the ice potential and there’s still plenty of time for changes to happen.
 
And since we're talking about CAD and warm noses and their model biases, it's worth noting that phenomena are, to some degree, two sides of the same coin. Perhaps somewhat counterintuitively, strong warm air advection above the boundary layer is really good for CAD. It creates a strong temperature inversion, which is really where the cold air at the surface derives its stability from. Because of that inversion, the cold air faces even more resistance if it tries to rise upward (over the mountain range).

In some ways, I wonder if the model bias of making CAD too weak has the same underlying reason as the bias to make warm noses too weak.
 
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