December 2025 Short/Medium Range Forecast Thread

[John1122]

The Euro AI has a very potent cold front in early December that really battles the SE ridge. It slowly overtakes the western forum first and it takes 36 hours or so to cross the state. Get some rain to snow in NW Tennessee that slowly spreads eastward and lightens as it goes east. Often times the cold comes a little quicker than models manage it in those situations, but sometimes it just sticks in place.

[John1122]

The cold is wild in the midwest. 40 degrees below normal with -10s. Most of our forum area is in the 10 to 20 degrees bn range from the 3rd to the end of the run on the 6th.

[John1122]

The Euro might be trying to go at a winter storm for the western areas at 288 this run. It's warmer than the AI but cooler across our forum area with less extremes on either side of the front.

[John1122]

The Euro ends up cutting the mid-state with western areas miserable in the 30s with rain, warm in the east ahead of the cutter. SE ridge wins on it vs the AI.

[jaxjagman]

Id agree with what Jeff said up above .We seem to be seeing the the SSW underway with the sharp rise in temps  into the stratosphere but even so ,the cold seems to be getting pushed back seemingly each day.The JMA  right now shows a strong MJO signal in the WP into the first of Dec,while this isnt bad it still should have reflection to  more or less a SER,just transient cold shots.Might not be a bad thing if you want a cold Christmas or even possibly beyond that for a couple weeks anyways

[jaxjagman]

GEFS looks more Euro now with any SSW,you can see it here

[jaxjagman]

In case you dont have this you can look at Planetary and Equatorial Waves using the Euro Modes,ill shut up now

[Carvers Gap]

The flip has been quick!  The trend has not been our friend, but it is only November and we have just begun to fight...or something like that.

The pivot away from BN heights over Tenn Valley has voluminous support both in width and depth in the model world.  From ensembles to Weeklies....the trend is towards a standing wave SER over the SE.  It can be beaten down, but it immediately returns.  

Outlier models such at the Euro AIFS and GEPS persist.  I don't discount those.  If cold is coming, the Canadian model will see it first.  What we really want to see is the GFS deterministic to start bringing cold eastward OR the Euro control weeklies.  That Weeklies Euro control is a nifty tool.  With the exception of a few days earlier this week, it simply refused to be cold for December.

The repeated troughs into the Southwest are an ominous look if you like snow and cold.  I keep asking myself this question, "Have I been burned more by Baja lows which actually formed...OR have I been burned more by modeling which erroneously (due to feedback) put that feature in the Southwest?"  I guess we will find out soon!  Modeling often performs so poorly over that region.

I find it pretty hard to believe that the MJO in phase 8 is going to end up being warm.  So, I do think there will be some moderation(from AN heights) back towards seasonal and maybe even BN heights at some point for a 7-10 day period during December.  The Euro Weeklies today are cold at the surface, but I now think that is a bad, bad bias(and a new one at that) and an error.  Its 500 heights are now pretty much AN for most of December.  That would imply cold will push some, but the SER is the base pattern.

Again, this is shoulder season, and trends will likely still change - we can hope, right?!  However, for me anyway, my hopes that models are delaying the cold diminish with each passing run.  The reality is that it might not come to pass for much of December.  But it only takes one memorable snowstorm to make folks forget a warm pattern!  Besides, we usually don't get a lot of tracking in the valleys until January or Feb.  

We aren't even gonna talk about the retrograding BN heights(over the HB) into the West to start January!  If LR ext modeling was wrong about December cold, it could certainly be wrong about a January pattern at range!  I wish I had better news.  I will give it a few more days, and then I will almost certainly have to adjust my winter ideas.  

Have a good weekend, everyone!  At least we are getting some much needed rain.

[Carvers Gap]

If the Baja/Southwest cutoff is simply feedback, we should start to see the slp slowly creep eastward with each run, especially the first (in a series of 3!).  If that is indeed feedback, you can bet the rest of the (previous runs) are probably not correct.  Something to watch on this rainy, fall night.