December 2025 OBS and Discussion

[MJO812]

[cleetussnow]

8 hours ago, Brian5671 said:

Not sure why cold matters on xmas-it's an indoor holiday.    Whether it's 12 or 56 you're sitting inside

What?  I don’t know where to start with this.

[jm1220]

23 minutes ago, MJO812 said:

Regular GFS squishes it like a bug, congrats-ish DC to Cape May. Didn’t even know there was an AI GFS.

[eduggs]

Far NW suburbs still on track for a possible C-2" tomorrow. Unlike last week which was more of a latitudinal gradient, this potential wintry event has a stronger elevational component.

I could see the top of Schunnemunk or Mt. Beacon getting an inch or two of snow while the Hudson River towns get zilch. Elevated NW NJ could get a little accumulation this time too.

[anthonymm]

Threat for Sunday looks impotent

[MJO812]

29 minutes ago, jm1220 said:

Regular GFS squishes it like a bug, congrats-ish DC to Cape May. Didn’t even know there was an AI GFS.

There is also a cmc para. AI is taking over everything. 

[eduggs]

Sunday isn't lost yet. The next day or so will likely resolve whether or not this is a potential wintry threat. The ICON, ECM-AI, GFS-AI, and GEFS support a possible snowstorm. The other guidance (UK, ECM, CMC, GEPS, EPS) aren't too far off.

[eduggs]

5 minutes ago, anthonymm said:

I expect consensus from the 0z's tonight that it will trend to a nothing burger. Central park could get just a T of snow for December if sunday doesn't materialize (we start torching around the 20th). That means go super low this winter (10"ish or less).

I get the pessimistic sentiment. I feel it too. But the reality is we just don't know how things will play out. Some of our best snowstorms seemingly came out of nowhere. And the positive surprises are more fun than fretting for a week about a modeled blizzard that might disappear. 

[MJO812]

AI Euro and euro are more amped

[Krs4Lfe]

7 minutes ago, anthonymm said:

I expect consensus from the 0z's tonight that it will trend to a nothing burger. Central park could get just a T of snow for December if sunday doesn't materialize (we start torching around the 20th). That means go super low this winter (10"ish or less).

 

Just now, eduggs said:

I get the pessimistic sentiment. I feel it too. But the reality is we just don't know how things will play out. Some of our best snowstorms seemingly came out of nowhere. And the positive surprises are more fun than fretting for a week about a modeled blizzard that might disappear. 

Unfortunately, in this fast flow pattern that has been dominant since 2019, I doubt storms will pop up out of nowhere. I think if there’s enough storminess around, one will come our way. 

[brooklynwx99]

this is why it’s sometimes not as simple as worse PNA -> weaker storm… the TPV is better oriented and allows the vort to curl more on the ECMWF

[NEG NAO]

33 minutes ago, MJO812 said:

There is also a cmc para. AI is taking over everything. 

pretty soon we won't even have to post on here AI will post for us knowing what we would say and when we would say it

[WeatherGeek2025]

8 minutes ago, NEG NAO said:

pretty soon we won't even have to post on here AI will post for us knowing what we would say and when we would say it

i don't think I want that!

[eduggs]

I'd take those ECM runs every time. Weekend, daytime snow. 8-12hr duration. Temps freezing or below. We pray.

[donsutherland1]

It will turn briefly milder tomorrow. Some rain showers are likely tomorrow night. Some wet snow showers could occur well north and west of New York City. It will then turn somewhat cooler for the remainder of the week, but the cold won't match today's chill.

Light precipitation is possible during the weekend, especially on Sunday.

The ongoing stretch of below normal temperatures will likely continue into or through the second week of December. December 1-10 will be a solidly colder than normal period. The potential exists for the coldest first 10 days of December since at least 2007 (33.4°, 5th coldest December 1-10 since 2000).

The five coldest December 1-10 periods since 2000 were:

1. 30.6°, 2002
2. 32.2°, 2003
3. 32.4°, 2000
4. 33.1°, 2005
5. 33.4°, 2007

All 5 of these cases had measurable snowfall in Central Park.

The WPO is forecast to become strongly negative beyond December 10th. That would likely contribute to the December 10-20 period also being colder to perhaps much colder than normal overall.

The probability that December 2025 will have a maximum monthly temperature below 60° is increasing. The last time that happened was in 2019 when the monthly high was 58°. If 2025 has a monthly high below 60°, that would be only the fifth such occurrence since 2000 (2003, 2004, 2005, and 2019 are the cases since 2000).

The ENSO Region 1+2 anomaly was -0.2°C and the Region 3.4 anomaly was -0.5°C for the week centered around December 3. For the past six weeks, the ENSO Region 1+2 anomaly has averaged -0.27°C and the ENSO Region 3.4 anomaly has averaged -0.65°C. La Niña conditions will likely continue through at least mid-winter.

The SOI was +17.96 today. 

The preliminary Arctic Oscillation (AO) was -0.921 today. 

Based on sensitivity analysis applied to the latest guidance, there is an implied near 91% probability that New York City will have a cooler than normal December (1991-2020 normal). December will likely finish with a mean temperature near 34.1° (5.0° below normal). 

Supplemental Information: The projected mean would be 3.4° below the 1981-2010 normal monthly value. 

 

[qg_omega]

Historic torch is gearing up for second half of December, rubber band going to snap back hard

[MJO812]

14 minutes ago, qg_omega said:

Historic torch is gearing up for second half of December, rubber band going to snap back hard

Big troll 

[Krs4Lfe]

13 minutes ago, qg_omega said:

Historic torch is gearing up for second half of December, rubber band going to snap back hard

The only question remains: can we get 4” of snow at NYC before then? If we see a shutout for this month given how cold this month has been, that’s a big yikes 

[wishcast_hater]

17 minutes ago, qg_omega said:

Historic torch is gearing up for second half of December, rubber band going to snap back hard

Normal temps is not a torch.

[SnowGoose69]

Despite the change on the 18Z runs the ingredients for this are still in no man’s land.  This was stated by someone on the SNE forum too.   I think this will change about two times over in the next 36-48 hours.  There is even a risk for this thing to be a rainer honestly given the setup but I’d still lean towards a miss being the more likely fail 

[CPcantmeasuresnow]

1 hour ago, qg_omega said:

Historic torch is gearing up for second half of December, rubber band going to snap back hard

Maybe look up the definition of the word historic. I don't think you're using it correctly. 

[CPcantmeasuresnow]

3 hours ago, NEG NAO said:

pretty soon we won't even have to post on here AI will post for us knowing what we would say and when we would say it

Will it know about the damaging effects of the sun angle on snow accumulations?

[mob1]

ICON completely lost Sunday's wave 

[MJO812]

2 minutes ago, mob1 said:

ICON completely lost Sunday's wave 

Laughable changes

[eduggs]

FWIW, the RGEM at 84hr looks more like the 18z ICON than 0z. The RGEM has a more pronounced shortwave over the Dakotas and the PV is further north. The 0z ICON is much more suppressive with lower heights / the PV through the Lakes.

[SnowGoose69]

1 minute ago, eduggs said:

FWIW, the RGEM at 84hr looks more like the 18z ICON than 0z. The RGEM has a more pronounced shortwave over the Dakotas and the PV is further north. The 0z ICON is much more suppressive with lower heights / the PV through the Lakes.

Yeah was coming to say this.  Even the NAM was that way though at 84 the NAM is a mess anyway most times