December 2025 Short/Medium Range Forecast Thread

[Carvers Gap]

The 12z AIFS pushes back pretty heavily on the chinook - even more so than the 6z GFS.   Take one look at the 500 map, and it doesn't look great.  But take a look at what is creeping into Greenland.  That is a game changer if it stands(and doesn't connect to a WAR).

 

But take a look at the surface.  Not what you would expect.  That isn't warm.  Cold air is seeping into the EC.  A cold hp over the GL is not a bad thing for us. FWIW, the 12z GFS looked ready to break the chinook look by the end of its run.  The NAO firing will force everything south.

 

[Matthew70]

1 hour ago, Daniel Boone said:

Thanks brother ! I hope and pray your Wife gets well and you stay healthy. Dr said Flu was bad here too. He said Covid was too but it's Symptoms haven't been as bad as the other Viruses.

Thank you!  Yes hopefully the flu shot will help me some if I get it.  Having the damaged lungs from Covid.  I need to avoid any flu.  I know vaccines can be a dirty word for many but I have to take any precautions I can. 

[Daniel Boone]

1 hour ago, Carvers Gap said:

The 12z AIFS pushes back pretty heavily on the chinook - even more so than the 6z GFS.   Take one look at the 500 map, and it doesn't look great.  But take a look at what is creeping into Greenland.  That is a game changer if it stands(and doesn't connect to a WAR).

 

But take a look at the surface.  Not what you would expect.  That isn't warm.  Cold air is seeping into the EC.  A cold hp over the GL is not a bad thing for us. FWIW, the 12z GFS looked ready to break the chinook look by the end of its run.  The NAO firing will force everything south.

 

That's the evolution of getting that pesky GOA Low moved. Force that sucker South and West . The Central Ridge gets forced back West from the classic blocking that looks to be setting up..if that 50-50 is real, that'll be the real deal blocking Pattern.

[BooneWX]

2 hours ago, Daniel Boone said:

Yeah. I still have this Upper Respiratory Virus. 12 days so far. Dr says it has now led to a Sinus and bronchial Infection. So, yeah would be a nice break with a mild period and more moisture in the air. Be careful out and about folks. Alot of nasty stuff going around. Dr even said the regular cold virus is stronger and harder to shake than usual.

I’ve got a kid in daycare and it’s been an absolute nightmare of viruses since September really. This fall and winter has been a sick season on steroids.

[Carvers Gap]

19 minutes ago, BooneWX said:

I’ve got a kid in daycare and it’s been an absolute nightmare of viruses since September really. This fall and winter has been a sick season on steroids.

Yeah, cold and viruses have been making laps in my crew.  Pretty miserable stuff and hangs on forever as @Daniel Boonenoted.  

Hopefully the 12z Euro Weeklies are right and we see cold return right after mid-January.  The 12z CFSv2 breaks for cold at about the same time.  

It looks like when the NAO fires(if it fires), that puts a clock on the chinook.  Maybe if that NAO can fire earlier, we can return to a colder pattern more quickly.  But really, I am good with a couple of weeks of warm weather.  Something makes me think the dam is gonna bust at some point sooner than later.  One good cutter, and it could all come south.

[Golf757075]

2 minutes ago, Carvers Gap said:

Yeah, cold and viruses have been making laps in my crew.  Pretty miserable stuff and hangs on forever as @Daniel Boonenoted.  

Hopefully the 12z Euro Weeklies are right and we see cold return right after mid-January.  The 12z CFSv2 breaks for cold at about the same time.  

It looks like when the NAO fires(if it fires), that puts a clock on the chinook.  Maybe if that NAO can fire earlier, we can return to a colder pattern more quickly.  But really, I am good with a couple of weeks of warm weather.  Something makes me think the dam is gonna bust at some point sooner than later.  One good cutter, and it could all come south.

I think a true pattern change will take place when the mjo starts to move. Takes a while to get out of warm patterns if they become established imo

[Carvers Gap]

That is a big time NAO on the 18z GFS run.  It doesn't have a lot of impact yet, and its staying power is TBD.  It may be a forced NAO which just results due to dynamics and is passing through, or it might be the SSW finally working its magic along w/ the QBO.  It could hook into the mid-continent ridge, but that generally would cause an NAO and subsequent cold outbreak about 3 weeks later...and has been a common feature of winters of late.

[Carvers Gap]

By 200, the NAO is having significant effects on the run compared to previous runs.  The 12z AIFS scores a coup if it nailed it first.

[Carvers Gap]

Wow.  If that NAO is real on the 18z GFS, it very well could force split flow...and you kind of see it at the end of this run.  That will completely upend modeling over the next few days if legit.  That would be a major player.  The 12z AIFS and 18z GFS now have this.

[Carvers Gap]

I think what we will see is the MJO slide into phase 6 as the NAO fires.  The mid continental ridge will hook into it briefly.  That will create a significant SSW.  The MJO will slide into 7-8 as the CHI charts showed over the weekend.  The entire cold air mass gets released into a full latitude trough over the US w/ the storm track south of the Ohio River Valley.  Good sign if it holds.  The NAO will work against us at first, but as it matures...that is when it pays off.

[Golf757075]

10 minutes ago, Carvers Gap said:

I think what we will see is the MJO slide into phase 6 as the NAO fires.  The mid continental ridge will hook into it briefly.  That will create a significant SSW.  The MJO will slide into 7-8 as the CHI charts showed over the weekend.  The entire cold air mass gets released into a full latitude trough over the US w/ the storm track south of the Ohio River Valley.  Good sign if it holds.  The NAO will work against us at first, but as it matures...that is when it pays off

Carver, that's good news if true! Op runs and ensembles will show a colder outcome if it's legit. If not, it won't imo.