December 2025 OBS and Discussion

[MJO812]

40 minutes ago, eduggs said:

The last two GFS op runs are well east of the GEFS mean days 5 through 6 with the shortwave and SLP in the east. The GEFS mean shows precipitation primarily in the lower MS valley while the op GFS shows it along and off the east coast. Discounting the op runs for now though an eastward trend is noted in the other mid-range op models. The GEFS seem to be somewhat of a compromise between the 12z EPS and GEPS. The GEFS would put us right on the edge of both significant precipitation and marginal temperatures for wintry precipitation. 

18z AI Euro ticked northwest. Gives the coast and Inland some accumulations.

[MJO812]

Anyone looking at the 0z gfs ? Nice snowstorm next week.

[bncho]

ka ching on the GFS

[eduggs]

Can't complain about the 0z GFS. We haven't had a widespread coastal snowstorm like that in a while. Gorgeous ouput! CMC, ICON, ECM, and ensembles close enough for interest. Hopefully no big swings from here on out (doubtful)... Small, incremental improvements would be ideal. We are still almost a week out, so it's still going to be tough to pull this off I think.

[MJO812]

4 minutes ago, eduggs said:

Can't complain about the 0z GFS. We haven't had a widespread coastal snowstorm like that in a while. Gorgeous ouput! CMC, ICON, ECM, and ensembles close enough for interest. Hopefully no big swings from here on out (doubtful)... Small, incremental improvements would be ideal. We are still almost a week out, so it's still going to be tough to pull this off I think.

Gfs is  active and cold . Nice to see.

[eduggs]

The UK is also an excellent run at 0z (both surface and aloft). Supports the GFS - maybe slightly better even.

[eduggs]

6 minutes ago, MJO812 said:

Gfs is an active and cold run. Nice to see.

The 0z GFS is an absolutely filthy glutton for snow. I'm going to pretend I didn't see the extended run and keep my personal focus on the mid-range.

[MJO812]

Just now, eduggs said:

The 0z GFS is an absolutely filthy glutton for snow. I'm going to pretend I didn't see the extended run and keep my personal focus on the mid-range.

Nice ridge out west and plenty of cold. What a turnaround from the models.

[eduggs]

1 minute ago, MJO812 said:

Nice ridge out west and plenty of cold. What a turnaround from the models.

The GFS retrogrades the CA ULL west into the Pacific. If that doesn't happen, the longwave flow across the US would be significantly altered. Our downstream weather is extremely sensitive to the modeled evolution of the western trof over this period. Could still end up balls cold or periodically torched days 6-15.

[MJO812]

Ukie is also on board with the storm along the front.

[eduggs]

0z GEFS is slightly drier/south compared to 18z. So the GFS and GEFS moved towards each other this run.

[Snowlover11]

[NEG NAO]

2 hours ago, MJO812 said:

Anyone looking at the 0z gfs ? Nice snowstorm next week.

The important feature is the strong enough cold enough HP in southeast Canada staying PUT long enough to keep feeding the cold enough air in and storm track is perfect Benchmark because of this

[NEG NAO]

The OZ UKMET looks to be a closer to the coast track as the HP in southeast Canada is not as strong - starting at least as Frozen in the metro - the Canadian and the Euro AI are offshore tracks

[NEG NAO]

The 0Z Euro starts as frozen in the metro BUT that HP does not stay anchored like in the GFS run so there is a change over to rain - still to early to predict the outcome except to say the storm chances are increasing and a frozen to rain scenario is favored right now IMO

[MJO812]

3 hours ago, NEG NAO said:

The 0Z Euro starts as frozen in the metro BUT that HP does not stay anchored like in the GFS run so there is a change over to rain - still to early to predict the outcome except to say the storm chances are increasing and a frozen to rain scenario is favored right now IMO

Quite possible. Just need the right track. Here is the 6z gfs 

[binbisso]

We can only go down from here. 

[Tatamy]

1 minute ago, binbisso said:

We can only go down from here. 

The clickbait crowd will be going into overdrive.  Imagine all the weather segments that will lead with this…

[Snowlover11]

Hell I’ll take 1/3 of that. I’m not falling into the trap! We will see come this weekend before getting excited.

[wdrag]

I84 corridor next Tuesday: A snow and ice event is modeled with uncertain amounts but may cause hazardous conditions. If you need to travel next Tuesday please monitor future forecasts.

I95 corridor-LI:  probably worth a pause before taking the bait. 

[North and West]

I’ll be the hater here: Why would we have such a big snowstorm down to the shore in an early part of the season (first week of December) when we usually don’t? (I’m aware that it’s snowed during this time in the past, et. al.) The universe usually aligns against it.

Ok, I’d enjoy being wrong, but interested in knowing why it would occur. Thank you and safe travels today!


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[jm1220]

If we can keep the western ridge, it should keep the SE ridge in check enough to give us a chance at a good storm track near the coast. There should be cold air to the north to pull down. But if we lose that ridge we risk it turning into a SWFE buzz kill because the SE ridge will respond and overwhelm it. 

[snowman19]

@forkyfork Thoughts on next week’s storm? 

[NEG NAO]

1 hour ago, North and West said:

I’ll be the hater here: Why would we have such a big snowstorm down to the shore in an early part of the season (first week of December) when we usually don’t? (I’m aware that it’s snowed during this time in the past, et. al.) The universe usually aligns against it.

Ok, I’d enjoy being wrong, but interested in knowing why it would occur. Thank you and safe travels today!


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Its rather easy to see why it would occur - that HP has to stay in place and block the storm into a favorable path for I-95 and provide the cold air source and be in a position to restrict the onshore warmer winds off the ocean - concentrate on the HP positioning

[bluewave]

December 3rd will probably be a good sample of what the storm tracks will do this winter. 

The last 7 winters we have seen a very dominant and fast Northern Steam of the Pacific Jet lead to three dominant storm tracks. 

Track #1 has been a Great Lakes cutter leading an amplified Southeast ridge and mostly rain near the coast. In this case there is enough separation in the fast Pacific flow for one system to really amplify pumping the Southeast ridge on the day of the storm. 

Track #2 featured just enough wave separation for an I-78 to I-84 hugger storm track. This has been a snow to sleet and rain scenario along the coast. A bit of a WAR or Western Atlantic ridge on storm day. 

Track #3 has seen kicker troughs coming into Western North America suppressing the Southern Stream storm tracks.

The Benchmark track with a record number of KU snowstorms which has dominated from 2010 to 2018 has been largely absent leading to the record low snowfall last 7 seasons. This has been a result of the much stronger Northern Stream of the Pacific Jet since 2018-2019.

If we can get the storm track on December 3rd to show some small deviation, then maybe we can see at least some small improvement this winter. We would want to see a deep enough coastal development near the Benchmark to have some hope in snowfall improvement this winter. 

Since 1995-1996 we have had 15 La Niña winters as defined by the RONI index. 14 out of 15 of those winters followed a repeating pattern which has been common the last 30 years. EWR, NYC, and LGA December snowfall pattern repeated throughout the entire winter. The Decembers with under 4” of snowfall at those stations went on to below average seasonal snowfall. With the Decembers over 4” or snow featuring average to naive average snowfall. 

You might ask how can this work out over 90% of the time?  My guess is that La Ninas tend to show what they are capable of early on in the season. Plus as our climate has warmed it has lead to more repeating and persistent patterns. So I view this December to winter snowfall relationship more as a marker of a deeper underlying shared pattern  rather than something that is directly causing the outcome.

[jm1220]

12 minutes ago, NEG NAO said:

Its rather easy to see why it would occur - that HP has to stay in place and block the storm into a favorable path for I-95 and provide the cold air source and be in a position to restrict the onshore warmer winds off the ocean - concentrate on the HP positioning

Yep, this time of year especially we need a strong cold air source on storm day, if that high slips east winds turn onshore and it’s game over. 

[psv88]

Water temp doesn’t matter if the wind is from the north. That’s how we’ve gotten snow in October and November down to the beaches 

[North and West]

Its rather easy to see why it would occur - that HP has to stay in place and block the storm into a favorable path for I-95 and provide the cold air source and be in a position to restrict the onshore warmer winds off the ocean - concentrate on the HP positioning

tyvm! I hope your idea verifies. Be nice to have everyone smile.


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[eduggs]

GEFS, EPS, and GEPS members clustered where we'd want them I think, mostly offshore with the SLP. Hints of a weak primary up the Apps. The bulk of the precipitation along the coastal plain. Surface temperatures for low elevation coastal areas are marginal for snow and the real cold doesn't move in until the storm is departing. But that's a pretty good look overall for a 6 day forecast.

The bar for me at this point of the season is a shovelable snowfall. I don't want to get carried away by 10:1 snow maps.

[jm1220]

1 minute ago, eduggs said:

GEFS, EPS, and GEPS members clustered where we'd want them I think, mostly offshore with the SLP. Hints of a weak primary up the Apps. The bulk of the precipitation along the coastal plain. Surface temperatures for low elevation coastal areas are marginal for snow and the real cold doesn't move in until the storm is departing. But that's a pretty good look overall for a 6 day forecast.

The bar for me at this point of the season is a shovelable snowfall. I don't want to get carried away by 10:1 snow maps.

We’ve had accumulating snow right down to the beaches in less than ideal cold-Nov 2018 being the most recent example but numerous others. We really just don’t want the wind shifting to onshore.