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Wintry Winter Storm Dec 7-10

malak05 said:
You believe the jet streak would open door to more convection and moisture from Gulf to northern portion
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You also don't see jet streaks like what the GFS is forecasting very often around here, anything above 90-100 knots is fantastic but 150-160+ is absolutely absurd except in cases where you have bombogenesis... I'm not saying that's going to happen or is really a legitimate or likely scenario, but if I didnt know better and had nothing else to look at, I would be giving it due consideration just based on that jet streak alone, it's insanely intense for our area of the world
 
I just don't see all that moisture being that suppressed as it is driven down and explodes in Gulf on GFS the CMC and NAM have similar tailing precip field but they lift inland
 
Was posted on the other board, GFS is the warmest of models right now on 2m temps​
 
malak05 said:
I just don't see all that moisture being that suppressed as it is driven down and explodes in Gulf on GFS the CMC and NAM have similar tailing precip field but they lift inland
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Even those models may not depict the full extent and intensity of the precipitation shield NW of the low. This situation has overperformance for the NW zones written all over it
 
gem_mslp_pcpn_frzn_us_13.png
 
Temps
 
I'll add in to what Webber is talking about. With this setup, you have to use high res models. With a powerful jet streak, there is going to be strong amplification within the SW flow. The SW flow is going to be convective, and as Webber mentioned, the snow is going to be wet and heavy.
 
RollTide18 said:
Definitely gotta be careful with the models when it comes to the precip shield, as seen with Snowpocalypse 2014.
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Yeah and this case even more so, you rarely see jet entrance regions in NC that are much better than what the GFS is depicting w/ this storm. Even if there's absolutely no change in the intensity and placement of the low, the axis of precipitation could shift northwest for this very reason of the model not being able to resolve isentropic lift on the NW side of the low and the expansion of the precipitation shield with a huge jet streak over the mid Atlantic...
 
I think there will be a narrow swath where someone gets lucky, just the right spot where heavy precip and just cold enough to lay down 2-3", but I think it will be a very narrow path. And who knows where that sweet spot will be

Sent from my SM-G920V using Tapatalk
 
Just a note, TT has this hidden but it's still on the website, here's the "Total Positive Snow Depth Change" for the CMC. Probably indicates that most areas in the 10:1 map will experience lots of flakes but little to no accumulation, which would make sense.
gem_asnowd_seus_18.png
 
The problem with the enhanced jet streak is as isohume just pointed out to me on another board is that the GFS cross sections show no deep omega coupling with very little in the way of low level forcing.
 
malak05 said:
Well 12z CMC is beat run it's had I days to that s huge especially since it mirrors NAM... I beginning to think Webber is onto something here with that jet stream
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"The problem with the enhanced jet streak is as isohume just pointed out to me on another board is that the GFS cross sections show no deep omega coupling with very little in the way of low level forcing."

It probably isn't far enough NW w/ the precipitation shield even though it's pretty far NW in its own right. The problem with Isohume's line of rationale is that there's really nice Q vector convergence all the way back into eastern Tennessee and the Apps of NC, VA, and even into West Virginia, which argues that may get something out of this as well even though many of the models don't show much quite yet and/or show little in the way of deep omega coupling for the moment.

(Q vectors essentially show the summation of differential vorticity advection and differential temperature advection which both contribute to lift in the quasi-geostrophic framework. Cyclonic vorticity advection and positive differential temperature advection (i.e. increasing warm air advection w/ height) both argue for ascent and vis versa. Sometimes you'll see cancellation of these parameters, you'll have warm air advection but anticyclonic vorticity advection so Q vectors help you flesh out these cancellation problems and wherever they're converging, large-scale ascent is favored and vis versa. Below you'll notice the Q vector convergence (shaded in red) over the SE US where ascent is favored and vis versa over the Mississippi Valley where Q vector divergence argues for descent.)
24818908_10207676293265064_1679619767_o.jpg
 
Webberweather53 said:
"The problem with the enhanced jet streak is as isohume just pointed out to me on another board is that the GFS cross sections show no deep omega coupling with very little in the way of low level forcing."

It probably isn't far enough NW w/ the precipitation shield even though it's pretty far NW in its own right. The problem with Isohume's line of rationale is that there's really nice Q vector convergence all the way back into eastern Tennessee and the Apps of NC, VA, and even into West Virginia, which argues that may get something out of this as well even though many of the models don't show much quite yet and/or show little in the way of deep omega coupling for the moment.

(Q vectors essentially show the summation of differential vorticity advection and differential temperature advection which both contribute to lift in the quasi-geostrophic framework. Cyclonic vorticity advection and positive differential temperature advection (i.e. increasing warm air advection w/ height) both argue for ascent and vis versa. Sometimes you'll see cancellation of these parameters, you'll have warm air advection but anticyclonic vorticity advection so Q vectors help you flesh out these cancellation problems and wherever they're converging, large-scale ascent is favored and vis versa. Below you'll notice the Q vector convergence (shaded in red) over the SE US where ascent is favored and vis versa over the Mississippi Valley where Q vector divergence argues for descent.)
View attachment 1818
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Even the 500 hPa omega on the GFS is impressive already all the way into the southern Delmarva and central VA. If it's not handling the precipitation shield right, and/or QG forcing for ascent, or the low track, (among other things) then this omega coupling forecast and rationale is also erroneous.
us_f78.png
 
Just as a friendly reminder wrt what the canonical NW trend is capable of even inside 4-5 days, look what happened to the European's depiction of this first frontal wave that will bring mostly a cold rain on Thursday to many on the forum (although a couple flakes can't be entirely ruled out). Solid shift of at least 150-200 miles to the northwest and still shifting

0z run 48 hours ago
ecmwf_ptype_nc_18.png


0z run this morning
ecmwf_ptype_nc_10.png
 
Webberweather53 said:
Just as a friendly reminder wrt what the canonical NW trend is capable of even inside 4-5 days, look what happened to the European's depiction of this first frontal wave that will bring mostly a cold rain on Thursday to many on the forum (although a couple flakes can't be entirely ruled out). Solid shift of at least 150-200 miles to the northwest and still shifting

0z run 48 hours ago
View attachment 1821


0z run this morning
View attachment 1820
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Given the similar structure, intensity, evolution, and character of this first frontal wave on Thursday to the one we'll have to deal with later on Friday that could bring some wintry precipitation, I think the depiction of the first frontal wave in the models serves as a valid general benchmark for how the models could trend with our system going forward (although it may not be as extreme or perhaps even more so).
 
Just something to remember as well, the models are notorious for being too quick with CAA. Don't be surprised if the snow line isn't 100-150 miles NW of where the models initially have it even a day before the event.

Secondly, watch for Evaporative cooling and dew points. This is one of the reasons why the Snow Jam nailed us.
 
Arcc said:
Just something to remember as well, the models are notorious for being too quick with CAA. Don't be surprised if the snow line isn't 100-150 miles NW of where the models initially have it even a day before the event.

Secondly, watch for Evaporative cooling and dew points. This is one of the reasons why the Snow Jam nailed us.
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Meanwhile local only wanna talk about a clipper and not mentioning this possibility. It’s hysterical
 
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