December 2025 OBS and Discussion

[bluewave]

2 hours ago, NorthShoreWx said:

We spiked to 48.4 at 9:40 am and are down 2 degrees since. That's been happening a lot recently with the max, or at least a secondary max before 10am.  I have no explanation for why.  I noticed the same on a couple of other local sensors.

Made it to 49° here with the MOS and raw guidance forecast for low 40s. Noticed the MOS from several days ago was around 50° but it shifted colder. Models often underestimate highs with sunny and windy downslope flow and the cold air lagging frontal passage.

[MJO812]

Eps again was too torchy in the long range.  Take the long range with a grain of salt. 

 

 

 

New run is colder

[North and West]

Eps again was too torchy in the long range.  Take the long range with a grain of salt. 
 
 
 
New run is colder

Honest question, why does everyone lose their minds with long range models (no matter that they show), when they’re just going to change anyway? It’s a seasonal tradition.


.

[MJO812]

8 minutes ago, North and West said:

Honest question, why does everyone lose their minds with long range models (no matter that they show), when they’re just going to change anyway? It’s a seasonal tradition.


.

Yep

[steve392]

I'm really really getting sick of this wind every single dam day.  

[donsutherland1]

Tomorrow will be a bit cooler with temperatures returning to the upper 30s. A weak system will bring some light snow or snow showers to the region on Tuesday. There is a chance that New York City could pick up a coating but a measurable snowfall is not a guaranteed outcome for the City. A 1"-2" snowfall is possible in the distant northern and western suburbs where it will be colder.

The temperature will likely remain above freezing throughout the day on Tuesday. In New York City, only 25.6% of storms have seen measurable snowfall with a daily low of 33° or above with just 9.2% seeing 1" or more snowfall. Almost three-quarters (74.4%) of such events have seen only a trace of snowfall.

No exceptionally cold or warm weather appears likely for the first week of astronomical winter.

The closing week of December could experience periodic warmer and cooler days. 

The probability that December 2025 will have a maximum monthly temperature below 60° has increased further. 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 -0.3°C and the Region 3.4 anomaly was -0.7°C for the week centered around December 10. For the past six weeks, the ENSO Region 1+2 anomaly has averaged -0.33°C and the ENSO Region 3.4 anomaly has averaged -0.67°C. La Niña conditions will likely continue through at least mid-winter.

The SOI was +13.96 today. 

The preliminary Arctic Oscillation (AO) was +1.100 today. The PNA was -1.604. That is the lowest winter value since January 8, 2023 when the PNA stood at -1.618.

Based on sensitivity analysis applied to the latest guidance, there is an implied near 100% probability that New York City will have a cooler than normal December (1991-2020 normal). December will likely finish with a mean temperature near 34.6° (4.5° below normal). 

Supplemental Information: The projected mean would be 2.8° below the 1981-2010 normal monthly value. 

 

[qg_omega]

Very windy, gusting into the 40s to near 50

[lee59]

Temperature down to 35 and wind gusting to 28mph

[happyclam13]

3 hours ago, MJO812 said:

Eps again was too torchy in the long range.  Take the long range with a grain of salt. 

 

 

 

New run is colder

This is misleading 

[Stormlover74]

16 minutes ago, happyclam13 said:

This is misleading 

Clams are only happy at high tide 

[North and West]

This is misleading 

I’ll take the bait, el clamino… Why is it? It looks different, right?




.

[eduggs]

I think Friday still bears some watching. A few ECM runs and GFS-AI run the precipitation into a wall of CAD. Lots of northerly low level drain. It's a much better threat for New England, but there's still enough time and enough ensemble spread... Pretty low likelihood however outside of some ice across the northern interior or maybe flakes to end.

[MJO812]

1 hour ago, happyclam13 said:

This is misleading 

How happyclam sauce ?

[sussexcountyobs]

Currently:

Clear. Breezy. 24.6°

[eduggs]

I don't put too much stock in the GFS-AI, but it's showing snow and ice for Friday 12/26:  >0.5 liquid with surface temps at or below freezing NYC north throughout the event. It has hinted at this wintry outcome for several cycles. There is a little support amongst the ensembles, particularly the ECM suite, but the majority of mid-range guidance takes the boundary well north of us, favoring NNE for wintry precip. 

[MJO812]

2 minutes ago, eduggs said:

I don't put too much stock in the GFS-AI, but it's showing snow and ice for Friday 12/26:  >0.5 liquid with surface temps at or below freezing NYC north throughout the event. It has hinted at this wintry outcome for several cycles. There is a little support amongst the ensembles, particularly the ECM suite, but the majority of mid-range guidance takes the boundary well north of us, favoring NNE for wintry precip. 

AI gfs shows a snowstorm

New 0z gfs

[eduggs]

0z GFS has a significant snowstorm for Friday.

[MJO812]

2 minutes ago, eduggs said:

0z GFS has a significant snowstorm for Friday.

With the block its possible but need the others on board. 

[eduggs]

That's a big shift from the GFS. It represents the southern edge of its ensemble spread from 12z and 18z as well as several of the ECM ens members. We pray! If it's real we would expect to see movement from other models over the next day or two. I'm doubtful for now but the ECM has been hinting at this possibility...

[eduggs]

Don't even look at the GFS "clown" maps for Friday. You will not be able to unsee them.

[MJO812]

7 minutes ago, eduggs said:

Don't even look at the GFS "clown" maps for Friday. You will not be able to unsee them.

Cmc is also further south but north of gfs. Feeling the block.

[MJO812]

1 minute ago, MJO812 said:

Cmc is also further south but north of gfs. Feeling the block.

 

[David-LI]

[Wxoutlooksblog]

58 minutes ago, eduggs said:

I don't put too much stock in the GFS-AI, but it's showing snow and ice for Friday 12/26:  >0.5 liquid with surface temps at or below freezing NYC north throughout the event. It has hinted at this wintry outcome for several cycles. There is a little support amongst the ensembles, particularly the ECM suite, but the majority of mid-range guidance takes the boundary well north of us, favoring NNE for wintry precip. 

Operational GFS is mostly snow for that event and a good amount of it. It shows a more suppressed storm track primary low dies over the Appalachians and re-develops well offshore east of Delmarva Peninsula. We'll see this change more than a few times over the next 3 days. I think it's worth watching. 18Z Euro AI had storm track right over us with nothing but rain.

WX/PT

[MJO812]

1 minute ago, Wxoutlooksblog said:

Operational GFS is mostly snow for that event and a good amount of it. It shows a more suppressed storm track primary low dies over the Appalachians and re-develops well offshore east of Delmarva Peninsula. We'll see this change more than a few times over the next 3 days. I think it's worth watching.

WX/PT

Gefs also shifted well south of 18z. Ukie also shifted south.  Nothing like the gfs as of right now.

[Wxoutlooksblog]

5 minutes ago, MJO812 said:

Gefs also shifted well south of 18z. Ukie also shifted south.  Nothing like the gfs as of right now.

I think it's fair to say that in the last 24 hours this potential storm has become more interesting and that if trends continued it could open up the possibility of a mostly frozen or even a mostly snow event Friday. But there's a lot of *ifs* there.

WX/PT

[NEG NAO]

18 minutes ago, Wxoutlooksblog said:

I think it's fair to say that in the last 24 hours this potential storm has become more interesting and that if trends continued it could open up the possibility of a mostly frozen or even a mostly snow event Friday. But there's a lot of *ifs* there.

WX/PT

IF's And's or But's -all involving where that HP is in southeast Canada and the strength of it throughout the event- pattern is changing back into a colder one along with more blocking developing

[binbisso]

00z ecmwf ai is also south snow to rain.

[MJO812]

Euro !

[David-LI]

2 minutes ago, MJO812 said:

Euro !

have a snow map?