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]

Based on ensemble guidance seen through 06z/28, a rapidly intensifying and fast moving coastal low will bring a variety of weather elements to the NYC subforum. Periods of moderate to heavy rain are expected coastal areas- preceded by a little snow-sleet near dawn Tuesday and to closeout the storm Tuesday evening, while a period of heavy snow-sleet seems likely for the interior, especially the I84 corridor. Gusty northerly winds to 45 MPH are possible for eastern Long Island in the early Wednesday morning departure.  

Due to the late development and rapid departure of the storm, the chance of coastal flooding is minimal. 

All ensembles including ECAI have significant precipitation.

This may be Central Parks first measurable snow-sleet of the season, though temps at or just above freezing at sunrise Tuesday may preclude onset measurable in the city.

Delays are anticipated over the interior hilly terrain with possible school closings or early dismissals along and north of I80, especially the I84 corridor from the Poconos across se NYS into CT.

One attached graphic (WSSI-P) shows the potential for a minor impact event per the NWS inputs for the their 1AM Friday forecast. 

[CPcantmeasuresnow]

It's early but starting to like the looks of this for those of us 35 miles or more north of the city, especially with some elevation 500 feet and up. 

[psv88]

Not seeing any frozen for the city and coast. Classic interior event, and even they may change to rain. Wash, rinse, repeat. 

[eduggs]

The 12z is the 4th cycle in a row that the CMC has shifted south with the vortmax... it had been up in Ohio/Great Lakes more like the GFS. The two models show important differences at day 4 with the 6z ECM kind of a compromise.

[eduggs]

Just now, psv88 said:

Not seeing any frozen for the city and coast. Classic interior event, and even they may change to rain. Wash, rinse, repeat. 

We don't know exactly how this event will play out yet. But even if it ends up an interior event, non-elevated NNJ through the lower Hudson Valley haven't had a decent snow event in a while. So this wouldn't really be a repeat scenario in that sense.

[snywx]

17 minutes ago, CPcantmeasuresnow said:

It's early but starting to like the looks of this for those of us 35 miles or more north of the city, especially with some elevation 500 feet and up. 

I don’t see elevation really being a factor other than if/when the transition occurs to either rain or ZR. Latitude is gonna be the key here. At 4 days out , it’s really looking like 84 is gonna be the marker between warning level snows & nuisance event 

[CPcantmeasuresnow]

1 minute ago, snywx said:

I don’t see elevation really being a factor other than if/when the transition occurs to either rain or ZR. Latitude is gonna be the key here. 84 is really looking like the dividing line between warning level snows & nuisance event 

Not in the mid to later stages of the storm but n the beginning stages when temperatures are marginal elevation wont hurt. 

[snywx]

1 minute ago, CPcantmeasuresnow said:

Not in the mid to later stages of the storm but n the beginning stages when temperatures are marginal elevation wont hurt. 

Agreed. That 1-2 degree difference could make a difference Initally with accumulation

[NEG NAO]

42 minutes ago, eduggs said:

The 12z is the 4th cycle in a row that the CMC has shifted south with the vortmax... it had been up in Ohio/Great Lakes more like the GFS. The two models show important differences at day 4 with the 6z ECM kind of a compromise.

and this is the result

[eduggs]

1 hour ago, snywx said:

I don’t see elevation really being a factor other than if/when the transition occurs to either rain or ZR. Latitude is gonna be the key here. At 4 days out , it’s really looking like 84 is gonna be the marker between warning level snows & nuisance event 

Agreed. While it's possible the Newburgh waterfront on the Hudson is a slushy 33F vs. 32F and accumulating snow at Stewart airport, the model soundings say elevation along the transition zone might only matter in terms of rain vs. ZR.

[hudsonvalley21]

18 minutes ago, eduggs said:

Agreed. While it's possible the Newburgh waterfront on the Hudson is a slushy 33F vs. 32F and accumulating snow at Stewart airport, the model soundings say elevation along the transition zone might only matter in terms of rain vs. ZR.

That result has happened many times. In addition, up on top of Storm King Mountain, is an even snowier outcome.  And all are within a 5 mile radius.

[eduggs]

ECM-AI is on board for some snow I-95 NW. Accumulations maybe just west of there with moderate snow accumulations inland. The ECM is similar. Pretty good consensus with the GFS warmest at the moment.

[wdrag]

12z/28 ECAI OPPPPP took a big step north in concert with its prior cycle  ensembles. 

EC op has tiny touch of snow acc Tuesday night in the storms departure on w and n LI... garbage but maybe it will be something? 

Plan for less and enjoy mPing if its provides hope Tue AM and Tue night. 

 

Four days away so still model adjustments will occur.  n/c to threadline attm. 

[NEG NAO]

10 minutes ago, wdrag said:

12z/28 ECAI OPPPPP took a big step north in concert with its prior cycle  ensembles. 

EC op has tiny touch of snow acc Tuesday night in the storms departure on w and n LI... garbage but maybe it will be something? 

Plan for less and enjoy mPing if its provides hope Tue AM and Tue night. 

 

Four days away so still model adjustments will occur.  n/c to threadline attm. 

I wouldn't change the thread title till Sunday PM if needed - IMO this setup is not set in stone as 25 -50 miles either way makes a big difference..along with the position of the HP and how the storm cutting through the Great Lakes this weekend adjusts the location of the key players on the field....

[NEG NAO]

This is what I mean by 25 -50 mile adjustment 12Z Euro has snow accumulations now down into central NJ and part of Ocean/Burlington  County NJ

[psv88]

15 minutes ago, NEG NAO said:

This is what I mean by 25 -50 mile adjustment 12Z Euro has snow accumulations now down into central NJ and part of Ocean/Burlington  County NJ

At 10:1 that’s white rain at the coast 

[NEG NAO]

[eduggs]

Everything looks relatively encouraging for I-95 NW except the GFS. It's insistent on a packet of vorticity and associated sharp shortwave tracking from MO through OH through northern NY. Most other guidance is AR through KY through PA or SNJ. 

If a shortwave tracks that far NW it will be very hard to keep snow anywhere along the coastal plain. From memory I feel like if any model sees this kind of shortwave tracking near the Lakes with a coastal SLP, it ends up verifying. 

[WeatherGeek2025]

6 minutes ago, eduggs said:

Everything looks relatively encouraging for I-95 NW except the GFS. It's insistent on a packet of vorticity and associated sharp shortwave tracking from MO through OH through northern NY. Most other guidance is AR through KY through PA or SNJ. 

If a shortwave tracks that far NW it will be very hard to keep snow anywhere along the coastal plain. From memory I feel like if any model sees this kind of shortwave tracking near the Lakes with a coastal SLP, it ends up verifying. 

hopefully this keeps trending south? how is the euro look 18z?

[MJO812]

Euro and Euro AI are slightly south and east. Gfs is alone.

[MJO812]

18z euro AI eps gives the coast and just inland a few inches.

[MJO812]

18z eps is further east

[eduggs]

50 minutes ago, MJO812 said:

18z euro AI eps gives the coast and just inland a few inches.

The ECM is a strange solution. Its precip. field is well southeast of the 12z EPS and the shortwave is less impressive than 12z, but it still rapidly deepens the SLP into the 970mbs near the benchmark. The ECM family and the GFS are not close. Much more overlap between the ensemble means.