Carvers Gap

Really great runs by the 18z GFS and AIGFS. The good thing is that there are now a few windows of winter weather opportunity during prime climatology. And so far(famous last words)...the 500 pattern has not been can kicked. The EPO ridge is set to arrive on Jan 8th-9th. We wait all year to track in this time frame. Some years, we aren't able to track in mid-late January at all. Take advantage of it when and if you have the time. For those of us who have patiently tracked this, I hope our patience is rewarded. Kind of a fun thing to track a pattern for several weeks, have the 500 pattern verify, and then maybe get 1-2 winter events with that. Doesn't always work out that way, but it is rewarding when it does. As for details, I am cautiously optimistic that we will see winter weather return w/ the eastern trough. Been burned too many times to ever throw around absolutes in this hobby. But for now, it looks good.

Again, I want to remind folks to beware of ensemble means at d10+. There are a very few warm solutions which are skewing the mean. If there was a median, it would almost assuredly be cold at 12z. I like this look at 500. The PV at 500 is over NA and not Asia. Some may correctly point out that is 3336...Yes, it is. However, the vortex is almost in place by about 272 on this side of the pole. The 12z GEFS is far more aggressive than this. I chose the least aggressive. But for fun, switch your model to Northern Hemisphere view and 500 Geopotential height...and watch the cold develop over NA. IF this occurs, ensembles are highly likely to be too warm after 300.

At 500 and the surface, the 12z GFS, CMC, and Euro are remarkably in sync for the duration of their runs through 360 - western ridge and eastern trough w/ vortices diving into the eastern trough and a somewhat active STJ(differences exist w/ it).

Sorry, here is an edit. The EPO ridge should begin sliding into place between Jan 8-9th. That is only 4-5 days out, and looks like it will be legit. What follows synoptically should be several vortices diving into the downstream eastern trough which forms as a result of the West coast ridge - that last sentence is TBD in regards to details. But I just wanted to clarify that we are only about 96 hours from the EPO ridge(could be some PNA in that) forming along the West Coast.

The pattern is still on schedule to send the ridge west by Jan 8-9 w/ those mechanics underway now. So, to me the first legit window(excluding the light snow that possibly falls next weekend at the onset of the pattern change) sits right tentatively around Jan 14th w/ another right around the 20th - reference Cosgrove. Just impossible to know right now what/if interaction the northern stream has with the STJ. I like the Euro at this time of year, but the GFS isn't far from the same solution. Good trends. Once we get to the 14th, it really looks like one window after another until the ridge retrogrades into Asia, we wait about a week, and then do it all over again to end January and begin February. I still like a 95-96(lite) pattern evolution. Whether we can get they type of snow? IDK.

At minimum, what the 12z Euro is advertising would likely provide northern stream vortices w/ some light snow for portions of the forum areas.

This is an example of the potential where this could go. With it being right around d10-11, certainly this will change some. Interestingly, you can see the first trough over the Mountain West beginning to give way to the second trough in the Eastern Pacific.

The 12z Euro, and I can only see the 500 map at the moment, shows the trough deepen as a second wave drops into the trough around the 14th. That "should" yield a window if true. The Euro gets a bit of a nod as it has been steady with the ridge/trough progression. It seems the Euro is about to score the win w/ EPO. It had it first and wouldn't budge...the control actually had it first if memory serves me correctly.

As this ridge retrogrades, in my mind I think we see a window where it sits in the right spot (nearly perfectly). If there is cold air available, I think that is when we see the worst of winter delivered. The 12z GFS, though flawed, shows an example of how this could happened right at the end of its run. Be sure to look at 500 anomalies - you can see it better. As the ridge shifts West, the initial ridge is just too far to the East. As it retrogrades, is slides into the sweet spot where cold can really get southward. With the STJ showing a less dormant look....that is the window. The reason the GFS is dry on this run is that it slowed down the retrograde considerably....so the initial trough is too far to the east to connect w/ the STJ. As long as the ridge continues to retrograde, at some point that trough is going to be right over the Tenn and Ohio river valleys IMHO. As for how the ridge retrogrades, see my comments from the last few days. I think the pattern retrogrades that ridge into Asia....then does it again. That fits the MJO rotation and blocking pattern. I do think the base pattern has a lot of HL blocking FWIW.

What's up, everybody? The 12z suite is rolling. There are some really good looks embedded in modeling. As noted, the AI GFS is loaded. The GFS is is very progressive as its bias. Details are starting to come into focus with the pattern change sitting right at 7-8 days out. The 12z CMC has light snow next weekend over portions of the forum area, and then looked ready to roll aa the model ended. Cosgrove(off the top of my head)noted in his update last night that the window of Jan13-15 has potential for a winter storm from Texas to DelMarVa. I agree with that. He noted another window just around or after Jan 20. I also agree with that. Interestingly, and we talked about this a few pages ago, he noted that a Baja low may well eject the energy used in one of those winter storms. I generally don't mind rain in LA. That, in my mind, has tended to correlate to snow over MBY at some point.

The 12z AI GFS on the other hand.....is winter. But yeah, the GFS has had issues.

Haha. The 18z GEFS on WX Bell has found the cold!!! EPO doin’ the work…

The 18z GFS is again honking w/ overrunning and the AIFS Euro is similar. Those tracks and setups will change at this point...but at least modeling is throwing out some good solutions.

TRI ended 2025 w the biggest snow departures in all of E TN. I think Knoxville ended up w/ more which is unusual. I won't be bashful this year if TRI scores some snow.

Shocked...I mean I am shocked that the ensembles have suddenly found cold air on a continent that was without it(on LR modeling) for days. Not really.