Re: DECEMBER 16th 17th 2020 Snow Threat???

by **jmanley32** Mon Dec 14, 2020 9:29 am

Frank_Wx wrote:NWS is not messing around. Area wide Godzilla

Wow, where did you get that? I do not even care that I am not in the red, 12-18 is amazing, even 6-12 is awesome to be talking area wide. I just have a hinkering that it will be widespread 12+.

by **nutleyblizzard** Mon Dec 14, 2020 9:29 am

12z Nam has stronger confluence along with a more robust western ridge. Hold on folks this run could be a biggie...

by **SoulSingMG** Mon Dec 14, 2020 9:30 am

jmanley32 wrote:
SoulSingMG wrote:

6z RGEM drops the hammer on NYC.

Yeah thats the K ratio, I would take that with less than a grain of salt, the movement of the Euro to take the city into the 6-8 inch range makes it very hard for be to believe 24+ on rgem, but who knows maybe the SR know something the LR do not, we are getting into SR soon.

Definitely a pipe dream snow map, buuuut I like the RGEM at this range and it’s been wicked consistent for 24 hrs. Big 12z runs coming; NAM already looks like she’s finding her way back south this run due to >er confluence.

by **jmanley32** Mon Dec 14, 2020 9:32 am

At hr 60 NAM is a bit more east of the 06z, I think that could bode well.

by bobjohnsonforthehall Mon Dec 14, 2020 9:34 am

jmanley32 wrote:At hr 60 NAM is a bit more east of the 06z, I think that could bode well.

Indeed. Confluence seems better. If NAM moves a fair amount I would discount looking at it at all until maybe 36 hours out. When it is very consistent this far out it needs to be considered. If it waffles, toss it until it is in close range.

by **billg315** Mon Dec 14, 2020 9:34 am

12z NAM keeps the surface Low tucked in over the Delmarva and right on the NJ coast with significant mixing issues all the way up to just north of NYC proper and Long Island. Most significant accumulations limited to north of I-78. Still brings about 6-12" of snow to most people north of I-78, but the cut-off goes from like a foot of snow north to about a couple inches in about a 5-10 mile range. That is sharp.

by **Frank_Wx** Mon Dec 14, 2020 9:36 am

In my opinion, the small shift S-SE on the NAM was not enough. The general idea is we get very heavy snow before dry slotting and/or changeover to mix. It's still a big difference compared to just 24 hours ago.

by **billg315** Mon Dec 14, 2020 9:37 am

Heaviest snows continue to stay back in Central PA on the NAM.

by **algae888** Mon Dec 14, 2020 9:43 am

Frank_Wx wrote:In my opinion, the small shift S-SE on the NAM was not enough. The general idea is we get very heavy snow before dry slotting and/or changeover to mix. It's still a big difference compared to just 24 hours ago.

It's still the nam at 60 plus hours. I'll take it more seriously tomorrow at 12 Z sometimes it does get systems right but most of the time it's too amped up it is definitely the Western edge of guidance which would be a good thing because I still think the entire Tri-State area gets at least 6 inches of snow whether or not we mix or change to rain or dry slot that is a significant snow storm for December

by **rb924119** Mon Dec 14, 2020 9:44 am

Frank_Wx wrote:In my opinion, the small shift S-SE on the NAM was not enough. The general idea is we get very heavy snow before dry slotting and/or changeover to mix. It's still a big difference compared to just 24 hours ago.

Agree, Frank. The surface depictions are wrong, I don’t know what else to say. You have mid-level closed lows passing to our west/overhead and then even northwest of us at H5, embedded in deep-layer southwesterly flow; you aren’t going to magically see those circulations stop dead and jump due east. Sorry. If anything, they will eventually arc, but not before they reach and/or exceed our latitude. And this is actually projected quite well on the QPF maps getting the banding well to our north and west with the dry slot showing up for us. People can say that it shifted east and colder, but dynamically speaking it didn’t at all. And, in these setups, warm air advancement aloft always outpaces modeling, so I would a quicker transition from snow to slop.

by **jmanley32** Mon Dec 14, 2020 9:45 am

billg315 wrote:12z NAM keeps the surface Low tucked in over the Delmarva and right on the NJ coast with significant mixing issues all the way up to just north of NYC proper and Long Island. Most significant accumulations limited to north of I-78. Still brings about 6-12" of snow to most people north of I-78, but the cut-off goes from like a foot of snow north to about a couple inches in about a 5-10 mile range. That is sharp.

Southern westchester which is like 10-15 miles north of NYC on the snow map sees close to 12, thats nothinbg to scoff at but it is def razor thin, but the mix never actually makes it up that far on TT anyways.

by **jmanley32** Mon Dec 14, 2020 9:47 am

rb924119 wrote:
Frank_Wx wrote:In my opinion, the small shift S-SE on the NAM was not enough. The general idea is we get very heavy snow before dry slotting and/or changeover to mix. It's still a big difference compared to just 24 hours ago.

Agree, Frank. The surface depictions are wrong, I don’t know what else to say. You have mid-level closed lows passing to our west/overhead and then even northwest of us at H5, embedded in deep-layer southwesterly flow; you aren’t going to magically see those circulations stop dead and jump due east. Sorry. If anything, they will eventually arc, but not before they reach and/or exceed our latitude. And this is actually projected quite well on the QPF maps getting the banding well to our north and west with the dry slot showing up for us. People can say that it shifted east and colder, but dynamically speaking it didn’t at all. And, in these setups, warm air advancement aloft always outpaces modeling, so I would a quicker transition from snow to slop.

No slop lease, theres nothing i hate more in terms of weather. Well a cold nasty rain i guess. If its super windy slop could also mean power outages and wind maps are impressive, not sure how with such a weak LP but many see gusts 40-55mph for a period Wed Night.

by **jmanley32** Mon Dec 14, 2020 9:50 am

12z Nam looks quite good to me no? NYC on north doesnt see a lot less accumulation than most other models. The rgem is likely on roids but it would be awesome to happen. But I rarely see this kinda snow for my area so I would take it in a heartbeat. However I do see how the heaviest is now in PA and even up to syracuse, I guess I told my sister wrong that she wouldnt see sig snow, I'll have to revoke that possibly.

DECEMBER 16th 17th 2020 Snow Threat??? - Page 16 Namcon11

by **aiannone** Mon Dec 14, 2020 9:55 am

Bernie's latest video saying 3-6" for LI due to significant mixing and NYC hes concerned won't see more than 6"

by **jmanley32** Mon Dec 14, 2020 9:56 am

aiannone wrote:Bernie's latest video saying 3-6" for LI due to significant mixing and NYC hes concerned won't see more than 6"

This seems to be going from a godzilla to maybe a mothreazilla for a lot of people....I hope it changes.

by **Frank_Wx** Mon Dec 14, 2020 9:58 am

aiannone wrote:Bernie's latest video saying 3-6" for LI due to significant mixing and NYC hes concerned won't see more than 6"

On the low side for sure, but at this juncture, I agree there will be either significant mixing or dry slotting that occurs for the coast unless trends today quickly reverse.

by **nutleyblizzard** Mon Dec 14, 2020 10:01 am

rb924119 wrote:
Frank_Wx wrote:In my opinion, the small shift S-SE on the NAM was not enough. The general idea is we get very heavy snow before dry slotting and/or changeover to mix. It's still a big difference compared to just 24 hours ago.

Agree, Frank. The surface depictions are wrong, I don’t know what else to say. You have mid-level closed lows passing to our west/overhead and then even northwest of us at H5, embedded in deep-layer southwesterly flow; you aren’t going to magically see those circulations stop dead and jump due east. Sorry. If anything, they will eventually arc, but not before they reach and/or exceed our latitude. And this is actually projected quite well on the QPF maps getting the banding well to our north and west with the dry slot showing up for us. People can say that it shifted east and colder, but dynamically speaking it didn’t at all. And, in these setups, warm air advancement aloft always outpaces modeling, so I would a quicker transition from snow to slop.

I have to disagree with you RB. We have a strong high along with a powerhouse 50/50 low. I can’t see a primary low plow right into that. The Nam showed some improvements with stronger confluence and a bit better H5 setup. I take it as a positive for us. Man I love this hobby. Onto the Gfs.

by bobjohnsonforthehall Mon Dec 14, 2020 10:02 am

I don't see how those totals in Upstate NY verify. That high is no joke. Tough for me to see Albany get anywhere near the 14/15 inch line.

by **jmanley32** Mon Dec 14, 2020 10:07 am

bobjohnsonforthehall wrote:I don't see how those totals in Upstate NY verify. That high is no joke. Tough for me to see Albany get anywhere near the 14/15 inch line.

Even syracuse sees 6 plus inches!!

by **dsix85** Mon Dec 14, 2020 10:09 am

Any chance we are seeing the windshield wiper effect? Models inconsistent?

by **aiannone** Mon Dec 14, 2020 10:14 am

RGEM coming in and looks to hold.

by **aiannone** Mon Dec 14, 2020 10:16 am

ICON mostly rain for NYC and LI. Mixing in NNJ and SCT otherwise jackpot is up towards 684

by **nutleyblizzard** Mon Dec 14, 2020 10:17 am

dsix85 wrote:Any chance we are seeing the windshield wiper effect? Models inconsistent?

Models have a tendency to underestimate confluence. I expect continued corrections South and east although I believe the GFS is too far south.

by **aiannone** Mon Dec 14, 2020 10:18 am

aiannone wrote:ICON mostly rain for NYC and LI. Mixing in NNJ and SCT otherwise jackpot is up towards 684

DECEMBER 16th 17th 2020 Snow Threat??? - Page 16 13142710

by **Irish** Mon Dec 14, 2020 10:25 am

SoulSingMG wrote:
jmanley32 wrote:
SoulSingMG wrote:

6z RGEM drops the hammer on NYC.

Yeah thats the K ratio, I would take that with less than a grain of salt, the movement of the Euro to take the city into the 6-8 inch range makes it very hard for be to believe 24+ on rgem, but who knows maybe the SR know something the LR do not, we are getting into SR soon.

Definitely a pipe dream snow map, buuuut I like the RGEM at this range and it’s been wicked consistent for 24 hrs. Big 12z runs coming; NAM already looks like she’s finding her way back south this run due to >er confluence.

Could the GFS been right on their call of this storm? Models look to be veering toward a more SE run, which makes sense with the blocking.

by **aiannone** Mon Dec 14, 2020 10:27 am

12Z RGEM. Did bump slightly NW but kept LI and NYC all snow. Nice stripe of 12+

DECEMBER 16th 17th 2020 Snow Threat??? - Page 16 Rgem_a10

by **rb924119** Mon Dec 14, 2020 10:33 am

nutleyblizzard wrote:
rb924119 wrote:
Frank_Wx wrote:In my opinion, the small shift S-SE on the NAM was not enough. The general idea is we get very heavy snow before dry slotting and/or changeover to mix. It's still a big difference compared to just 24 hours ago.

Agree, Frank. The surface depictions are wrong, I don’t know what else to say. You have mid-level closed lows passing to our west/overhead and then even northwest of us at H5, embedded in deep-layer southwesterly flow; you aren’t going to magically see those circulations stop dead and jump due east. Sorry. If anything, they will eventually arc, but not before they reach and/or exceed our latitude. And this is actually projected quite well on the QPF maps getting the banding well to our north and west with the dry slot showing up for us. People can say that it shifted east and colder, but dynamically speaking it didn’t at all. And, in these setups, warm air advancement aloft always outpaces modeling, so I would a quicker transition from snow to slop.
I have to disagree with you RB. We have a strong high along with a powerhouse 50/50 low. I can’t see a primary low plow right into that. The Nam showed some improvements with stronger confluence and a bit better H5 setup. I take it as a positive for us. Man I love this hobby. Onto the Gfs.

That’s fine, you can disagree, I won’t get upset Smile

so, the 50/50 low isn’t exactly 50/50; it’s more like 51-52N/50W, and although it’s blocked from heading further north, it has an escape route to the east beneath blocking as it feels the weakness created by the wave break ahead of it. As a result, the confluence has room to shift north as the warm advection raises heights ahead of our storm before being able to hold its ground. It’s this poleward and eastward flexion of the confluent zone “50/50” low that I have been arguing for days, and what allows the primaries to gain more latitude before the blocking gets a firm foothold. Also, this flexion allows the low-level high to begin slipping/building east over the northwestern Atlantic, which means you start drawing in a more modified airmass as opposed to if the high was pressing from the north or northwest, and also open a pathway further west.

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