Discussion OBS for minor to possibly moderate impact winter storm interior 4A Tue - midnight Tue 12/2/25, may bring first measurable snow-sleet to coastal areas including NYC

[wdrag]

This thread headline looks good based on casual look at info through 06z/29. NYC CP might see their first measurable snow-sleet.  Back later today.  Ensemble WSSI-P graphic -06z/29, and ensemble prob for 3+" of snow (legend color code probs) hopefully speak for themselves. 

[MJO812]

City should see a mix but just inland has a chance of accumulating snow 

Latest euro has came south and weaker. 

[NEG NAO]

8 hours ago, MJO812 said:

Cmc

Gfs shifted weaker

anyone who wants 2-4 or 3 -5 in the immediate metro away from any immediate coastal locations should hope for a weaker solution - the water temps are still too warm for an amped up solution which brings in that warmer air- we won't know for sure how this is going to play out until that Great Lakes low passes and HP moves into southeast Canada and if it is allowed to leave with the flow or stays put just long enough to provide cold enough air and keep the  storm off the coast

[weathermedic]

Upton AFD:

 

LONG TERM /TUESDAY THROUGH FRIDAY/...
Key Points:

* Low pressure may bring the first bout of winter weather to the
  area Tuesday into Tuesday night. There remains uncertainty in the
  low track, which will be critical in determining precipitation
  type. At this time, it looks like mainly rain at the coast with
  rain/snow line somewhere over the interior.

* Below normal temperatures through next Friday.

NBM closely followed during this timeframe.

The focus for this forecast period will remain on a potential
coastal low bringing wintry weather to the region Tuesday into
Tuesday night. Global models have trended farther NW with the low
track the last 24h, with many of the 12Z operationals just inside
the 40N...70W benchmark. The EPS/GEFS mean are farther SE, deeper,
and more clustered around the mean, but there are also more members
to the NW of the mean than recent days. While the Pac energy
associated with this southern branch storm system is about to come
onshore western Canada, there will likely be some run to run changes
that are often critical to precipitation type across the area. In
addition, with no blocking over the north Atlantic, high pressure
quickly lifts out of the Northeast as the storm approaches, allowing
for more of a marine influence and erosion of the cold air. This is
why it is too difficult this far out to mention snowfall totals.
What does appear to be more certain though is for a strong coastal
low to impact the region.

The forecast is more reflective of a consenus forecast. Such a track
favors a mainly rain event at the coast, with a rain/snow line
working inland. Inland locations have the best chance of seeing
winter weather impacts at this time. NBM probabilities for greater
than inch of snowfall range from 10-25 percent at the coast and 40-
70 percent inland. For an advisory level snow, these probabilities
are 0-10 percent and 20-40 percent, respectively.

High pressure will primarily in control for the second half of the
week, minus a cold frontal passage on Thursday.

[anthonymm]

8 hours ago, jm1220 said:

Too early to say and too many unknowns. A weaker system without good dynamics, weaker cold push in front of the storm, etc could ruin it even with a better track. Stronger storm obviously brings the possibility it's too amped and has strong onshore flow. I'd say there's a narrow Goldilocks zone for the city to get some decent snow, but very narrow with a dynamic enough system, good cold push and good track. The possibilities expand a lot more NW of the city which is the usual especially this time of year. 

thread the needle as always. just very hard for the city to good snows now in general, regardless of if its dec, jan or feb.

[wdrag]

My first indicators of how future modeling will go, the NAM and RGEM.  RGEM tends to be a warmer model.  NAM tends to be quite amped at times. Still, I need to know whether NYC is still in the game for first measurable of the season. If the NAM 60-84 have NYC in some sort of snow, especially early Tues...thats good news, not necessarily correct. If the RGEM is likewise earlier and colder  ptypes=qood news.  You'll be more to date than I but that's how I read Global tendencies (OFF the mesoscale models - NAM supposed to go away in 2026). I do think the GFS is and has been too amped but this will be a significant short wave cutting east across NJ 00z/Wed so I foresee intensification as it rips negatively out into the north Atlantic.  Tremendous RRQ lift from the St Law Valley 250MB 180 speed max.

[NEG NAO]

24 minutes ago, wdrag said:

My first indicators of how future modeling will go, the NAM and RGEM.  RGEM tends to be a warmer model.  NAM tends to be quite amped at times. Still, I need to know whether NYC is still in the game for first measurable of the season. If the NAM 60-84 have NYC in some sort of snow, especially early Tues...thats good news, not necessarily correct. If the RGEM is likewise earlier and colder  ptypes=qood news.  You'll be more to date than I but that's how I read Global tendencies (OFF the mesoscale models - NAM supposed to go away in 2026). I do think the GFS is and has been too amped but this will be a significant short wave cutting east across NJ 00z/Wed so I foresee intensification as it rips negatively out into the north Atlantic.  Tremendous RRQ lift from the St Law Valley 250MB 180 speed max.

12Z NAM amped hard to believe this is correct if you are saying the GFS is too amped

[wdrag]

For what this is worth... has anyone checked BOX, OKX and discussions...  I dont quite have time...  but I'm thinking this rapid transition of an end moving- strengthening shortwave across our area with strong LFQ and even stronger RRQ of 250-300MB jets may fit the bombogenesis profile.  Let us know if anyone has mentioned this?

PPP drops at least 24 MB in 24 hrs 12z Tue-12zWED.  I'm believing rapid intensification and now it's a matter of thermal profiles.  Going to be an interesting day in these parts with R+ LI and a "period "of S+ wet snow inland.

mPing of value Tuesday including the possibility of a northernly jet 40kt plus on the backside over LI as the storm rushes east northeast. 

[steve392]

Of course I change jobs and the snow possibilities plummet for my new work location vs old 

[wdrag]

Tech Attachment from 1989 attached> references an older set of models but the pattern still applies.

See the checklist.

https://www.weather.gov/media/erh/ta/ta88-17b.pdf

[hudsonvalley21]

7 minutes ago, wdrag said:

For what this is worth... has anyone checked BOX, OKX and discussions...  I dont quite have time...  but I'm thinking this rapid transition of an end moving- strengthening shortwave across our area with strong LFQ and even stronger RRQ of 250-300MB jets may fit the bombogenesis profile.  Let us know if anyone has mentioned this?

PPP drops at least 24 MB in 24 hrs 12z Tue-12zWED.  I'm believing rapid intensification and now it's a matter of thermal profiles.  Going to be an interesting day in these parts with R+ LI and a "period "of S+ wet snow inland.

mPing of value Tuesday including the possibility of a northernly jet 40kt plus on the backside over LI as the storm rushes east northeast. 

No mention in the AFD’s from either in regards to the shortwave.

[wdrag]

That's what I just saw as well.  Research prior to the birth of many younger mets. I still think it worthwhile for forecasters who have time, to run a quick check. 

[NEG NAO]

1 hour ago, wdrag said:

Tech Attachment from 1989 attached> references an older set of models but the pattern still applies.

See the checklist.

https://www.weather.gov/media/erh/ta/ta88-17b.pdf

Sounds like the type of discussions and articles Paul Dorian of Arcfield Weather would discuss on his site........

[NEG NAO]

12Z Canadian amped up again - discussion here has been the GFS is too wound up and the Canadian and Euro have been trending towards it and then backing off then flip floping - like to know which data ingested into the models or missing on certain runs is causing this

[MJO812]

14 minutes ago, NEG NAO said:

12Z Canadian amped up again - discussion here has been the GFS is too wound up and the Canadian and Euro have been trending towards it and then backing off then flip floping - like to know which data ingested into the models or missing on certain runs is causing this

Euro still flat 

[eduggs]

Not a fan of 12z. Noticable shift towards the GFS-like emphasis of vorticity near the Great Lakes and less in the South. This leads to quick warming of the boundary layer. This was observed across all guidance except the GFS, which shifted a touch towards the consensus. The duration has also been shortening. This is now looking like a relatively quick hitting 6-8 hours of precipitation. A few days ago is was stretched out across as much as 18-24 hours.

[jm1220]

48 minutes ago, NEG NAO said:

12Z Canadian amped up again - discussion here has been the GFS is too wound up and the Canadian and Euro have been trending towards it and then backing off then flip floping - like to know which data ingested into the models or missing on certain runs is causing this

I’m about done with this one. Expecting a washout IMBY and around the city. 

[NEG NAO]

1 hour ago, MJO812 said:

Euro still flat 

interesting where does the data input come from for the Euro model ? The output is much different then GFS and Canadian

[MJO812]

42 minutes ago, jm1220 said:

I’m about done with this one. Expecting a washout IMBY and around the city. 

Some flakes but mostly rain

[MJO812]

Nao will be negative next week

[psv88]

53 minutes ago, jm1220 said:

I’m about done with this one. Expecting a washout IMBY and around the city. 

Yea it’s all rain for us 

[wdrag]

You'd have to believe the Euro has more data and later input time... and more reliable (at least I do). I am sort of surprised it doesn't amp.  ECAI does amp and plenty of snow interior.  I'll be watching AI temps at 18z and 00z//3 carefully for trends on AI.

Banding of wet snow could be a problem for some tree branches just s of I84 in nw NJ sw CT. 

 

[anthonymm]

6 minutes ago, psv88 said:

Yea it’s all rain for us 

white rain for jersey city for an hour then rain

[MJO812]

3 minutes ago, anthonymm said:

white rain for jersey city for an hour then rain

Agree

More storms to come in December which should be favorable 

[anthonymm]

1 minute ago, MJO812 said:

Agree

More storms to come in December which should be favorable 

meh. we should be seeing more ensemble support but its not really panning out for the city proper.

[snowman19]

9 minutes ago, wdrag said:

You'd have to believe the Euro has more data and later input time... and more reliable (at least I do). I am sort of surprised it doesn't amp.  ECAI does amp and plenty of snow interior.  I'll be watching AI temps at 18z and 00z//3 carefully for trends on AI.

Banding of wet snow could be a problem for some tree branches just s of I84 in nw NJ sw CT. 

 

It looks like you are going to have to be 40+ miles N and NW of NYC (Orange, Sussex, Putnam) to get into accumulating snow from this one

[WeatherGeek2025]

29 minutes ago, snowman19 said:

It looks like you are going to have to be 40+ miles N and NW of NYC (Orange, Sussex, Putnam) to get into accumulating snow from this one

i would guess at this time it's yonkers and north for accumulating snow, possibly even northern Bronx may get on some action if it falls during the night as the storm intensifies and pulls out

[snywx]

Just now, WeatherGeek2025 said:

i would guess at this time it's yonkers and north for accumulating snow, possibly even northern Bronx may get on some action if it falls during the night as the storm intensifies and pulls out

You are gonna have to be N of 287 to even sniff accumulating snow w/this one 

[WeatherGeek2025]

24 minutes ago, snywx said:

You are gonna have to be N of 287 to even sniff accumulating snow w/this one 

i think this whiffs north and west folks to be honest! keeps trending south in the last 48 hours in my opinion!

[NEG NAO]

34 minutes ago, WeatherGeek2025 said:

i would guess at this time it's yonkers and north for accumulating snow, possibly even northern Bronx may get on some action if it falls during the night as the storm intensifies and pulls out

18Z Nam is saying way north of Yonkers till it snows - closer to Albany