December 2025 Short/Medium Range Forecast Thread

[John1122]

Ironically, the GFS ensembles agree more closely at 500 than the Euro in general, and not with it's OP which is a massive WC trough/EC ridge.

 

[Daniel Boone]

The MJO appears to be progressing ideally for our Area through December. However, the AO and NAO are not if guidance were to be right. Of course, those Domains cannot be forecasted with great accuracy, particularly the NAO. 

      The good thing that can mitigate the Effects of the positve Arctic Oscillation Modes is the weak south displaced PV. We saw that in 2015 and a couple recent Years. However, if you want much greater Odds for across the Board Snowstorms you want the Arctic Domain Negative. As witnessed , most notably in 2015, Northern Area's can do well as long as the PV is weak and displaced well South in Canada.

[jaxjagman]

11 hours ago, jaxjagman said:

Check it out this winter if the MJO gets back to P5,ill look for an archive but i doubt its the same

The MJO was fairly chaotic into Maritime/WP this cycle but it was into still the Maritome the first week of Nov,i need to go back and read it more thoroughly for myself,thanks for sharing this,John

[Carvers Gap]

Pretty chilly 12z suite incoming so far.  Triptofan shut me down last night…so I missed the torch!  LOL

[John1122]

GFS torched because it killed the MJO and headed it back kinda towards 6 in the COD.

[GBOVolz]

Pretty chilly 12z suite incoming so far.  Triptofan shut me down last night…so I missed the torch!  LOL

PowellVols is in. Had to start a new account, new email


.

[Carvers Gap]

59 minutes ago, GBOVolz said:

PowellVols is in. Had to start a new account, new email


.

Glad to have you back, man!!!

[Carvers Gap]

Pretty good 12z run from the 12z GDPS para and 12z Euro(Dr No?!)....

 

[Matthew70]

Let the snow fall as much as it would like in December!  

[Carvers Gap]

I should add that climatology kind of doesn't like snow during early December in the valleys.  But during the last 15 years, it has allowed for it.  Anyway, this was the GMON from yesterday.  22 days in phase 8!

[Carvers Gap]

@John1122 is definitely on the money with the 0z GFS not even getting to phase 8.  I "think" that GFS plot is hopefully an outlier.   But....definitely something to keep an eye on, and as always, a very keen observation from John to spot that.  I "think" the 12z GFS began to correct that.

I would take the GMON above and shift that stall to the phase 7/8 border.  If it was January, I would be far more concerned w/ the faster rotation into 6.  But really, I am always concerned it rotates back into 6 - even if it wasn't showing it!  

I wonder when/if the SSW begins to show at the end of deterministic runs.  By the end of next week, we may start to see that influence at the end of those deterministic runs.

[Carvers Gap]

One more thing in a flurry of posts, I am beginning to see evidence that the NAO may begin to fire.  It is notoriously hard to predict, but it is significant in both the CMC and Euro 12z runs.  It is very evident on the 12z EPS and to some extent the 12z GEPS.  That is a BIG difference between the CMC/Euro vs GFS.  

[Carvers Gap]

I am waiting on the 12z EPS to fully populate so I can grab 5 and 10 day maps of 500 anomalies.  But here is the deterministic d10-15.   NAO and EPO regions both look good.

[Carvers Gap]

I deleted the four map comparison of temps above.  WxBell hasn't loaded the 12z d10-15 temp maps for the EPS.  It had defaulted to 0z, and I didn't catch it until now.  I should be colder than the map that was originally posted.  Same deal for the GEPS.  

[Carvers Gap]

12z Euro at 300.  This will 100% change, but this is an example of what "could" occur if a cold front drags its heels in the Gulf.

 

[Carvers Gap]

Here are the d10-15 or d11-16 500 anomaly comparisons from the big four ensembles...Heights over Greenland are rising.  BN heights over the SE.  EPO/PNA ridge.  BN heights over Alaska.  It is correct that BN heights over Alaska don't teleconnect to BN heights over the SE as a general rule. But old school winters would have a cold Alaska and cold Southeast with an almost continuous cold feed from the Yukon into the Ohio Valley.  It isn't without precedent, but recent climo is more or less against it.  Interestingly, on the GEFS, the BN heights over Alaska are temporary and maybe on one other ensemble.  Either way, that is a pretty decent cold signal for the first half of December.  I won't rule out a big ridge rolling through for a few days.