Major Nor'easter snow storm (possible top 20) Noon Wednesday-Noon Thursday Dec 16-17, 2020

[SnowGoose69]

1 minute ago, jdj5211 said:

Can someone give me a current start time for the storm for NNJ on Wednesday? 

Probably 3-4pm.  As always though in a setup like this with a nearly north moving system with a strong high over Canada the start time could be a few hours earlier than it looks at this range 

[weatherbear5]

Just now, SnowGoose69 said:

Probably 3-4pm.  As always though in a setup like this with a nearly north moving system with a strong high over Canada the start time could be a few hours earlier than it looks at this range 

This. Warm Air Advection waits for no weenie

[coastalplainsnowman]

44 minutes ago, NJwx85 said:

We had a storm on Christmas Day, I think it was 2002 where we had a thunderstorm come through with heavy rain, lightning and dime sized hail at my parents house in Northern, NJ. After the storm passed it changed over to snow and I think we finished with around 8". One of the few storms that I remember that started as rain and ended as significant snow.

That was awesome.  Till then I had heard about 50 forecasts of  'the rain may turn back to snow'  since birth, of which exactly zero had materialized as anything measurable, until that nice storm delivered.  Even with all the snowy years since then, nothing has ever matched it in that regard.  Pretty sure it's the only time before or since that I've seen a storm start as substantial rain and end as accumulating snow.  I'm sure the history is different north and west of NYC tho.

[NJwx85]

8 minutes ago, SnowGoose69 said:

Yeah the NAM QPF depictions that run were very disjointed and ugly 

It has the 700mb low closing off over Eastern PA so it almost chokes off the coastal with a mid-level dry punch after the initial WAA.

[HeadInTheClouds]

6 minutes ago, snowman19 said:

IMO the GFS/GEFS end up being the most correct. They have been extremely consistent and unwavering for the last 2 days and make the most sense given the setup over SE Canada and the North Atlantic

Just because it's consistent doesn't make it right. So has the Euro, CMC and their ensembles. 

[NJwx85]

4 minutes ago, SnowGoose69 said:

Probably 3-4pm.  As always though in a setup like this with a nearly north moving system with a strong high over Canada the start time could be a few hours earlier than it looks at this range 

General rule of thumb, in early. out early. It might be pretty much over by 1-2AM on Thursday.

[snowman19]

Just now, HeadInTheClouds said:

Just because it's consistent doesn't make it right. So has the Euro, CMC and their ensembles. 

Right, but look at the setup over Canada and the Atlantic....you are not getting a tucked in/coastal hugging track with that. Also, think back to how many times models underestimate confluence 

[SnowGoose69]

5 minutes ago, coastalplainsnowman said:

That was awesome.  Till then I had heard about 50 forecasts of  'the rain may turn back to snow'  since birth, of which exactly zero had materialized as anything measurable, until that nice storm delivered.  Even with all the snowy years since then, nothing has ever matched it in that regard.  Pretty sure it's the only time before or since that I've seen a storm start as substantial rain and end as accumulating snow.  I'm sure the history is different north and west of NYC tho.

NYC itself and nearby generally needs a system to be stacked from the surface to 500 to see a rain changing to snow event.  Otherwise the system simply will be exiting too quickly to northeast or east.  The Christmas 2002 event was missed by just about all models.  The GFS was the only one which showed it consistently but at the time the GFS was 2 months old as far as its rebrand and merge with the AVN/MRF and NCEP/NWS offices were very skeptical of its solution.  The 00Z ETA bit on the idea on 12/25 but the 06-12Z runs came out and moved away from it.  At the point the Upton office dropped the WSW they had issued for NYC earlier that morning around 2am

[HeadInTheClouds]

28 minutes ago, snowman19 said:

Right, but look at the setup over Canada and the Atlantic....you are not getting a tucked in/coastal hugging track with that. Also, think back to how many times models underestimate confluence 

Yes you can up to a certain laltitude. Are you going to discount all the models besides GFS? The low is going to move north and then ene or east. Most models have it getting north of AC and then east which seems reasonable. The GFS is moving the low east 100 miles farther south and the northward precip field is pathetic. I will get more than the 1 inch it shows for me just by WAA alone. It will eventually adjust. Its the one model I wouldn't put my money on. 

[HeadInTheClouds]

27 minutes ago, Northof78 said:

NAM is colder and further S/E, but still a very odd solution overall without much precip really anywhere (actually surpressed with northern extent of precip)....would lean heavily away from NAM and towards CMC/Euro combo with a touch of GFS

It may not be right but how is it surpressed with northern precip? It gives 1 inch LE up to Albany. 

[jm1220]

12 minutes ago, snowman19 said:

Right, but look at the setup over Canada and the Atlantic....you are not getting a tucked in/coastal hugging track with that. Also, think back to how many times models underestimate confluence 

Yes and no. It will try to tuck in and hug the coast until it can’t anymore with the blocking. That’s really key- if it tucks into around Cape May or DE coast and then goes east we’re all fine. If that doesn’t happen until it’s near or past Atlantic City, we start to have problems near the coast. 

[weatherbear5]

Only out to 48 on the collaboration RGEM site, and only see the surface.

The low over the NW Atlantic is closer to 50-50, so that’s an improvement. Maybe it helps lock that high in better. TBD

[SnowGoose69]

Just now, jm1220 said:

Yes and no. It will try to tuck in and hug the coast until it can’t anymore with the blocking. That’s really key- if it tucks into around Cape May or DE coast and then goes east we’re all fine. If that doesn’t happen until it’s near or past Atlantic City, we start to have problems near the coast. 

That track would be okay in a true Miller A but this is sort of a hybrid with the surface low maturing later and further north which is why the 700-850 low tracks are further north and west.  If this developed 100 miles south we could tug the surface low in tighter up here and have no issue 

[Brian5671]

RGEM is a crush job verbatim

[MJO812]

3 minutes ago, Brian5671 said:

RGEM is a crush job verbatim

Came west but the high is strong 

[Brian5671]

4 minutes ago, MJO812 said:

Came west but the high is strong 

Low rides the coast up to ACY then shoots straight east...sign me up for that any day.

[Blizzardo]

1 minute ago, Brian5671 said:

Low rides the coast up to ACY then shoots straight east...sign me up for that any day.

except I'll take a stall just south of Long Island! lmao

[SnowGoose69]

3 minutes ago, Brian5671 said:

Low rides the coast up to ACY then shoots straight east...sign me up for that any day.

The RGEM is basically a 30 mile difference from the NAM and ICON.  Everything pushes east just a tad earlier.  

[SnoSki14]

I think the worst case for us is an initial thump followed by a mid level dry slot and then some backend snows as the low slides east. 

I don't see how anyone in the NYC area and nearby counties sees less than 6-10" in this setup even with mixing. 

[jdj5211]

RGEM has been pretty consistent with that path and snowfall totals the last few runs....12Z GFS running now...important run

[nycsnow]

Rgem is 20ish for nyc area. Solid 

[kat5hurricane]

6 minutes ago, jdj5211 said:

RGEM has been pretty consistent with that path and snowfall totals the last few runs....12Z GFS running now...important run

I'd be shocked if the GFS didn't correct north somewhat. We'll see...

[jm1220]

1 minute ago, kat5hurricane said:

I'd be shocked if the GFS didn't correct north somewhat. We'll see...

The GFS upgrade hopefully resolved the SE bias issue somewhat but it being on the south side of consensus is never great in my opinion. 

[David-LI]

[MJO812]

Gfs did tick west but it is still cold

[TriPol]

GFS caved

[Brian5671]

sharp northern cutoff of QPF on the GFS

[Northof78]

RGEM & GFS (to an extent the NAM) now in agreement for a MECS nearly area wide, there is a growing concensus of a sharp northern gradient and a pretty 'extreme' confluence cutoff...but likely mostly north of our subforum. 

[jdj5211]

Big hit on GFS...colder solution...not quite the CMC/RGEM/EURO but got closer

[Allsnow]

1 minute ago, TriPol said:

GFS caved

No. It’s a non event in sne