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Pattern December Doldrums 2025 🎄 ❄️

EmilyWx said:
I'm simply not a big fan of the troughing projected by ensembles(EPS and GEFS particularly) near Alaska. Please correct me if I'm wrong but this is a scenario in which yes there would be cold air but it would struggle to be a quality cold air source and one that consistently fleets quickly due to lack of established blocking upstream near Greenland and limited support for established 50/50 lows. Northern stream kinda squashes everything which would favor weak positively tilted troughing over the eastern CONUS and with limited confluence(from our SS) and heights ahead of any trough potentially only leading to weak low pressure systems over our area(this being said will gladly take the much needed rain). The frequent shortwaves/clippers from the NS could still lead to some snow especially for the mountains but it doesn't necessarily favor areas outside of climatological norm for early December. It's a tough look for the southeast right now but once the phase 8 MJO fully sets in(from what I've heard the lag usually takes roughly 5-10 days but that may be incorrect) we should be set up beautifully beginning 2nd week of December. View attachment 177616View attachment 177617
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That will be transient as westerly momentum/then an +EAMT eventually push that ridge east towards Alaska/Yukon mid-late Dec. Without any momentum loss and with an SSW reflection event, you're just not gonna get a persistent trough either over Alaska or the West.
 
SD said:
Pattern isn't terrible coming up its just not one that knocks my socks off. I wouldn't be shocked if we tried to sneak something in likely either a late blooming coastal or some weird overrunning messy thing. I also wouldn't be surprised to see a breakdown about week 2 into week 3. That said a breakdown probably gets replaced by a similar pattern potentially colder right around christmas.
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Definitely could see some kind of overrunning mess take shape especially for yall.
 
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Quite a bit more digging of shortwave of interest on 12z euro vs 0z euro. Also same thing on EURO AI. This could continue to juice up if this trend is real.


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It’s early, but first impressions are were sort of wasting a trough(y) eastern US and nothing is showing up on models. Yet. Yeah we’re not in our prime climo but you have to hope this isn’t it. Mountains should be able to squeeze a good event out in the next 2-3 weeks.
 
TriplePhaser said:
That will be transient as westerly momentum/then an +EAMT eventually push that ridge east towards Alaska/Yukon mid-late Dec. Without any momentum loss and with an SSW reflection event, you're just not gonna get a persistent trough either over Alaska or the West.
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Indeed, it’s there for under a week and W coast troughing is already pushed well inland by 12/16:
IMG_5820.pngIMG_5821.png
 
KyloG said:
The 85 corridor and points west can’t screw this up if they tried…

View attachment 177623
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I don't know what's up with the AIFS snowfall physics. Tomer Burg's p-type confidence maps make a bit more sense (in the context of the model) with snow chances along the Virginia border. The EPS is much drier on the same parameter, but snow is a bit further south along the NC/SC border. Then the GEFS is a nothingburger after leading the way in snowfall chances for several days... funny how these things work.

It seems there's no real winning here. Too much northern stream, and the system shears out. Too little, and the CAD goes MIA.
eps_f102.pnggefs_f102.pngaifs_ens_f102.png
 
GaWx said:
On Nov 29th, the WCS daily PDO rose from ~-0.81 to -0.52, the fastest daily rise since Sept. 2nd:

View attachment 177630
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It will be interesting to see if we're in the process of flipping to a predominantly +PDO. The PDO has been strongly negative since 2020 and predominantly negative for most of this century. Perhaps winters of old in the SE can make a comeback, soon.

Pacific Decadal Oscillation (PDO) | National Centers for Environmental Information (NCEI)

Information on the Pacific Decadal Oscillation (PDO), often described as a long-lived El Niño-like pattern of Pacific climate variability
www.ncei.noaa.gov www.ncei.noaa.gov
 
CNCsnwfan1210 said:
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Looks like the Alaskan ridge is trying to return on the latest EPS/AIFs ensemble LR.


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Its going to be interesting to see how quickly that happens. I think we try for a ridge bridge through AK later in December/first of January
 
A lot of people don't seem to realize just how incredible 12z Euro today was for even areas showing rain with p-type. I ran some soundings in Upstate SC and Northeast GA and almost every single one was pushing the border of that freezing line at all levels. Should that run have been a tick colder, you'd be seeing euro 12z all over the internet.
 
iwantsouthernsnow123 said:
A lot of people don't seem to realize just how incredible 12z Euro today was for even areas showing rain with p-type. I ran some soundings in Upstate SC and Northeast GA and almost every single one was pushing the border of that freezing line at all levels. Should that run have been a tick colder, you'd be seeing euro 12z all over the internet.
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I think the issue all along in this setup is that if you flex the wave a bit stronger, it becomes warmer. That's fine, but it's going to be challenging to get both decent precipitation AND keep it cold. But it's definitely worth watching, especially in the more northern areas of course.
 
griteater said:
I think the issue all along in this setup is that if you flex the wave a bit stronger, it becomes warmer. That's fine, but it's going to be challenging to get both decent precipitation AND keep it cold. But it's definitely worth watching, especially in the more northern areas of course.
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Yeah I agree, I'm hoping for a continuation of the suppression trend before the NW tick comes in. Still probably have a little bit of time. GFS and Euro has swapped places oddly enough.
 
Biggest issue I see at the moment with the pattern into mid-Dec is simply with the Pac Jet not extending far enough. Hopefully that increases in time, but you can see on the images here the lack of high pressure (and lack of associated cold surges) moving thru China - those add momentum to the Pac Jet. In some cases, too much momentum. But we need more of it to try and move the western ridging farther east into W North America.

Dec 1 EAMT.gif

Dec 1 EPS Jet.png
 
TriplePhaser said:
That will be transient as westerly momentum/then an +EAMT eventually push that ridge east towards Alaska/Yukon mid-late Dec. Without any momentum loss and with an SSW reflection event, you're just not gonna get a persistent trough either over Alaska or the West.
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Oh I fully agree once AAM rises that it will completely flip. I was mostly talking about the next week and a half or so.
 
The time period around Dec 10-11 looks a bit interesting to me with the Greenland ridging dropping south / TPV dropping into Maine & SE Canada / Ridge spiking off the west coast.

GFS isn't suppressive enough and the storm cuts. Everyone's favorite model (CMC) looks better

Dec 1 GFS.gif

Dec 1 CMC.gif
 
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