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

[kat5hurricane]

7 minutes ago, jm1220 said:

NAM is better but still not great or a huge hit for the city. Might be a start for better trends but we'll see.

700mb low still tracks over E PA and N NJ which brings mid level warm air in. Also drying out by 6z after initial thump. It does track a little south of 12z however which was over Port Jervis. We really want that tracking south of us if possible. Just north of that track will have the heaviest snow. 

I think it's pretty much a given that the heaviest snow will be well north of the city. At this point, it's about salvaging a 6-10 inch type event with the initial slug of precip..

[SnowGoose69]

Just now, jm1220 said:

These CCB bands are modeled so often but many times don't happen. It does have a vigorous 500 and 700mb low which close off for a time so I guess I could see that somewhere. 

The warm push and dry slot will destroy the temps and snow growth in that layer.  I don't think anyone who punches into that nose sees more than just ugly poor growth snow 

[weatherbear5]

If it weren’t for that damn warm nose around 700mb, we’d be Golden. A shame

[Brian5671]

2 minutes ago, Juturna said:

On the whole, we are a lot more "doom and gloom" compared to the other subforums. Comes with the territory of weather abuse we've gone through. Just need to keep a level head as best as possible. The runs earlier today just seemed a little TOO north, and I'll be glad if that ends up being the case. 

some of the comments are hilarious "this was never an NYC storm" after 3 days of hyping a blizzard....

[Barman49]

Both NAM's have the low going east then for whatever reason jump back west.  Not sure if this is feedback or something else.  But that seems to be affecting the outcomes with precip.

[RCNYILWX]

These CCB bands are modeled so often but many times don't happen. It does have a vigorous 500 and 700mb low which close off for a time so I guess I could see that somewhere. 

Only wraparound/CCB that I can remember really working out for a storm that didn't have a good track overall for the city and western and central LI was the Christmas 2002 noreaster. I guess you could kind of group in the late Feb 2010 Snowicane but that was an odd beast of a storm.

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[Irish]

15 minutes ago, wizard021 said:

get that pink south please away from me.

Rejecting the pink eh?  

[Brian5671]

2 minutes ago, kat5hurricane said:

I think it's pretty much a given that the heaviest snow will be well north of the city. At this point, it's about salvaging a 6-10 inch type event with the initial slug of precip..

10 inches would be a third of our seasonal total in 1 day

[SnowGoose69]

The 3km NAM flips JFK at 03z and LGA by 04z to sleet.  This is pretty much in line with what I have felt all day.  I can't see more than 6-7 inches at either place unless something January 87 like takes place in those few hours before

[Brian5671]

NAM map-I'm sure some of this is sleet

[bluewave]

4 minutes ago, RCNYILWX said:

The NAM was actually supposed to be replaced this past summer as part of replacing the entire modeling infrastructure with the GFS's FV3 core. This is the setup the ECMWF and UKMET have, with all their modeling under the same core, from global to meso to ensemble and weekly/seasonal.

Taking the NAM off line was pushed back because better verification needed to be seen of the GFS/FV3 doing the things the NAM does well as well as the NAM. The coming upgrade of the GFS, if it is a marked improvement, and that's obviously the goal of the effort, will eventually result in that timeline of the NAM being discontinued into focus. In addition, this newest upgrade of the HRRR may be the last significant one until the high res suite gets fully moved over to the FV3 as well.

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So will there be a new meso model related to the FV3 that replaces the NAM? The only thing that I can tell about the GFS v16 is that the cold bias appears to have been corrected. 

 

[jm1220]

Looking at soundings, by 3z many of us near the city could start changing to sleet. Warm nose comes in at 800-850mb and looks marginal there, howling SE wind coming in as well at that level. By 6z a sharp warm nose comes in at about 750mb and would certainly be sleet. But at that point not much may be falling. By 9z the warm nose recedes and column is below freezing except the surface which soundings have at about 32. Without this CCB feature behind the low it would probably be 3-6" in and near the city. Various warm layers start to mess things up fairly early. We need a better trend with the mid level lows. 

[David-LI]

3 minutes ago, SnowGoose69 said:

The 3km NAM flips JFK at 03z and LGA by 04z to sleet.  This is pretty much in line with what I have felt all day.  I can't see more than 6-7 inches at either place unless something January 87 like takes place in those few hours before

Like the low going sub 990?

[MJO812]

7 minutes ago, weatherbear5 said:

If it weren’t for that damn warm nose around 700mb, we’d be Golden. A shame

Hopefully the models resolve the warm nose. I wonder if the models are overdoing it and that sleet is actually snow. 

 

Temps stay around freezing 

[jm1220]

Just now, MJO812 said:

Hopefully the models resolve the warm nose. I wonder if the models are overdoing it and that sleet is actually snow. 

 

Temps stay around freezing 

Often the models are too warm near the ground and actually under-do the mid level warmth. The NAM shows a strong closed 700 low, that will bring in the warmth for sure. 

[JBG]

7 minutes ago, RCNYILWX said:

Only wraparound/CCB that I can remember really working out for a storm that didn't have a good track overall for the city and western and central LI was the Christmas 2002 noreaster. I guess you could kind of group in the late Feb 2010 Snowicane but that was an odd beast of a storm.

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And Christmas 1969. Remember that one?

[kat5hurricane]

8 minutes ago, Brian5671 said:

10 inches would be a third of our seasonal total in 1 day

Yep, we should be thrilled with that. I think that's the ceiling for us close to the city, 4-8 is probably a more realistic range.

[friedmators]

I would still love to see this.  An hour or two of just ridiculous snowfall rates before the changeover.

[Snowlover11]

meh big dryslot for nyc proper on the nam.

[weatherlogix]

31 minutes ago, JoshSnow said:

NAM is south and colder simple as that

yeah, nah, its not

[Northof78]

Wow, NAM....100% better....the warmest model now gives NE NJ/NYC 8" - 13"...

[wizard021]

Just now, Snowlover11 said:

meh big dryslot for nyc proper on the nam.

Jan 27 2011 dryslotted before the death banded ccb for 3 to 6 hours. Gota hope for that. Or something like Feb 2014 just a little east.

[jm1220]

Surface wind direction also isn't great on the NAM for a time from the city east. At 6z the low center is over DE Bay and winds are coming in from the ENE. That could drive parts of LI above freezing so could actually mean some rain. Something of a coastal front develops that gets Montauk to around 42F at 9z. This run is a bit of improvement but more work needed.  

[snowman19]

8 minutes ago, Brian5671 said:

NAM map-I'm sure some of this is sleet

Yep, that 10:1 map is wayyyy overdone. It counts sleet as snow and the NAM has sleet getting all the way up into Rockland County for a time. Here is the realistic NAM snowmap: https://www.tropicaltidbits.com/analysis/models/?model=namconus&region=neus&pkg=asnowd&runtime=2020121518&fh=51

[jm1220]

Just now, wizard021 said:

Jan 27 2011 dryslotted before the death banded ccb for 3 to 6 hours. Gota hope for that. Or something like Feb 2014 just a little east.

1/27/11 had an insane 500mb cutoff low that took a perfect track to nail us, and the initial batch of WAA snow shut off before the mid level warmth got here. It's a perfect example of the precip shutting off when the mid level warmth was here but the massive closed low crushed us that night. This won't be anything like that. The mid level low is actually deamplifying as it comes east. 

[SnoSki14]

Nam has more confluence and is significantly better for those 20+ miles north and west of the city. 

Is it just the off run or will it continue, we'll see. 

[weatherlogix]

18 minutes ago, jm1220 said:

These CCB bands are modeled so often but many times don't happen. It does have a vigorous 500 and 700mb low which close off for a time so I guess I could see that somewhere. 

once you dry slot it becomes very difficult to saturate the column again.....that run was not great for the city east

[nycsnow]

Just now, SnoSki14 said:

Nam has more confluence and is significantly better for those 20+ miles north and west of the city. 

Is it just the off run or will it continue, we'll see. 

Really won’t take much of a s/e shift at 00z for us all to win 

[weatherpruf]

5 minutes ago, wizard021 said:

Jan 27 2011 dryslotted before the death banded ccb for 3 to 6 hours. Gota hope for that. Or something like Feb 2014 just a little east.

Feb 2014 was forgettable around here, but it was always progged to be forgettable; we were forecast from the get go for warm nose. That one struggled to get to 3-4 of sleet here; the March sleet storm delivered more here. 

[weatherpruf]

5 minutes ago, jm1220 said:

1/27/11 had an insane 500mb cutoff low that took a perfect track to nail us, and the initial batch of WAA snow shut off before the mid level warmth got here. It's a perfect example of the precip shutting off when the mid level warmth was here but the massive closed low crushed us that night. This won't be anything like that. The mid level low is actually deamplifying as it comes east. 

It actually rained for a few hours that day. Woke up to 19 inches....