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

[David-LI]

Sharing with you my favorite free Doppler radar for the area

https://www.nbcnewyork.com/weather/

[wdrag]

Just now, MJO812 said:

The sleet is actually heavy snow on the Nam 

Hope you're right.  Dry slot implied your depiction above which also tells me trouble. . NMM3K too amped? Don't know.  NWS I think likes the 3K a lot.  I don't have a feel but once the 0 layer more than 25 MB thick (~800 ft above freezing)  gets modeled to within 20 miles of you and you don't have strong VV, and/or -8C ice nuclei either available or descending into the dry slot , it's trouble.  Models are very good, but imperfect on placement.  I'll favor the NAM 3k/HRRR but defer and hope you';re right about colder and I'm wrong. Right now, the zone of uncertainty needs to be briefed as such - clarity about range of impacts. 

[jm1220]

6 minutes ago, MJO812 said:

The sleet is actually heavy snow on the Nam 

The sleet gets held off for a while due to huge lift and heavy rates. Warm air comes in as the front end slows. 3k Nam has up to an inch liquid fallen already before 6z at Farmingdale. We’ll need it down here to overcome the southerly flow aloft. 

[MJO812]

2 minutes ago, jm1220 said:

The sleet gets held off for a while due to huge lift and heavy rates. Warm air comes in as the front end slows. 3k Nam has up to an inch liquid fallen already before 6z at Farmingdale. We’ll need it down here to overcome the southerly flow aloft. 

1040 high right now up north

It is doing its dirty work

[NJwx85]

Based on current radar trends Washington DC should be reporting snow soon. Historically speaking we should expect snow about 4 hours after that happens. So my guess is a start time of around 2-3PM from SW to NE.

[NJwx85]

Look at the CAD signature all the way down into Southern VA. This airmass is well locked in.

[nycsnow]

10 minutes ago, kat5hurricane said:

I think 4-8 is a reasonable call for the NYC area from south to north, been sticking with this call for a few days. The low track is less than ideal and those warm layers almost always overperform in these marginal situations, I expect a lot of sleet. These 12-18 inch forecasts is ridiculously bold IMO.

Upton going with 10-13 For boroughs which minus the nam every model matches 

[psv88]

1 hour ago, jm1220 said:

There's all types of nor'easters that can produce heavy snow or rain in this area. The only real definition of it is it produces strong northeast winds lol. The classic snowmaking ones here track off the coast and have the strong cold high in place. There are others that hug the coast or have a warm airmass in place. 

You’re gonna be surprised how long you stay snow where you are. Enjoy 

[NJwx85]

4 minutes ago, nycsnow said:

Upton going with 10-13 For boroughs which minus the nam every model matches 

The only way that most of NYC is going to see a double digit snowfall from this storm is if it comes in much stronger and earlier than expected or if the models are wrong about the dry slot/mixing coming in around midnight.

[nycsnow]

1 minute ago, NJwx85 said:

The only way that most of NYC is going to see a double digit snowfall from this storm is if it comes in much stronger and earlier than expected or if the models are wrong about the dry slot/mixing coming in around midnight.

Well we should be snowing by 3pm just gotta see how long it holds on

[mikem81]

Look at the surface conditions and the HRRR at this point....

[NJwx85]

3 minutes ago, nycsnow said:

Well we should be snowing by 3pm just gotta see how long it holds on

I think Northern Manhattan, Northern Queens and the Bronx are going to get close to 10". I don't see how SI, Southern Queens, Lower Manhattan or Brooklyn gets to 10" without a big surprise. 

[mikem81]

https://www.spc.noaa.gov/exper/mesoanalysis/new/viewsector.php?sector=17&parm=pmsl&underlay=1&source=1#

 

Great site...

[NJwx85]

The 12z RGEM looked good to me. Less profound of a dry slot and doesn't really shut off precip until around 12-13Z.

[MJO812]

Precip is already flying up here

[NJwx85]

 

[HVSnowLover]

I’d go with nam for temps this close to a storm. Either way it’s heavy snow to start that’s step 1. 

[MJO812]

3 minutes ago, NJwx85 said:

 

How can you compare both cities?

[Ed, snow and hurricane fan]

Rare poster, not popular, I am at work but you can check model initialization now at balloon sounding sites or how they have performed in near term of SPC mesoanalysis page (based off a model, but I assume reasonably accurate).  Are 12Z NAMs well initialized?  How are they at 3 hours?

 

Check models at this point before hugging.  Players all on the field.

[nycsnow]

1 minute ago, MJO812 said:

How can you compare both cities?

Yeah means 0 for up here lol

[nycsnow]

3 minutes ago, NJwx85 said:

 

Some places flipped back to snow there according  to radar 

[psv88]

7 minutes ago, NJwx85 said:

I think Northern Manhattan, Northern Queens and the Bronx are going to get close to 10". I don't see how SI, Southern Queens, Lower Manhattan or Brooklyn gets to 10" without a big surprise. 

If it snows at 3” an hour  for 4 hours that’s a foot of snow. There will be a massive wall of snow moving in the southern areas before a change over, which may not even occur

[dave0176]

5 minutes ago, NJwx85 said:

I think Northern Manhattan, Northern Queens and the Bronx are going to get close to 10". I don't see how SI, Southern Queens, Lower Manhattan or Brooklyn gets to 10" without a big surprise. 

Yeah I’m wondering now if I see a flake at all, a lot of times in these situations it’s comes in as sleet and as the surface temps warm we go to plain rain right away. I’ll predict 2-4” for me. Hope I’m wrong and I get more.

[sferic]

Is there a graphic the NWS provides which projects possible snow ratios?

[hazwoper]

1 minute ago, nycsnow said:

Some places flipped back to snow there according  to radar 

Just checking the Correlation Coefficient output, Roanoke certainly has not switched back.

[nycsnow]

Just now, hazwoper said:

Just checking the Correlation Coefficient output, Roanoke certainly has not switched back.

Read the tweets replying to him people said it was raining in Charlottesville they’re back to snow

[nycsnow]

Precip moving NE which is good if it was due north we’d be worried 

[jm1220]

22 minutes ago, psv88 said:

Western Suffolk upgraded to 8-14”, matches all guidance. We’re gonna rock

I'm thinking 6-9" for us, staying a little conservative. Maybe too much South Shore left in me. 

We'll need the heavy snow rates initially to hold off the warm air aloft. It can definitely happen but I think Upton's a little too high and the Euro too cold. 

Other areas: NJ shore less than 1" most places-NE winds off warm water are a killer. 

South Shore: 3-6", maybe 2-3" twin forks, also I-95 south of I-78 such as Trenton. Sleet comes in earlier here obviously and you deal with the ocean influence too so possibly some rain especially out east. Minor additional accum from CCB remnants. 

North Shore out to Wading River area and most of NYC: 6-9", more of the initial thump is snow, changes to sleet at the end of it. Freezes into cement after storm leaves and CCB remnant drops maybe 1-3" additional. Also 6-9" for I-78 corridor to PA border, 25 miles or more NW of I-95

Coastal CT, Westchester/Rockland, NJ I-80 and north 9-14", mostly snow with a little sleet possible at the closest the storm comes. Dryslot keeps amounts lower than further north. 

Orange, Putnam south of I-84, more than 25 miles away from CT coast, Sussex County NJ 14-18", all snow. Also dryslot may reach this area somewhat. 

Catskills, Poconos, I-84 corridor and north: 18-24" from deformation snow band and high ratios. 

 

[SnowGoose69]

7 minutes ago, MJO812 said:

How can you compare both cities?

He may be correct about the forecasts but the models did not indicate that.  I forecast for both places and I had them almost entirely FZRA PL from the start

[dave0176]

2 minutes ago, JoshSnow said:

Where are you located?

Coastal Middlesex right on the Arthur Kill