Carvers Gap

Eyes -> 18z GEFS and 18z AIFS EPS snow means for the entire run.

Better than tracking SLPs in the Lakes!!!

I am gonna ride w/ ensembles for about 24-36 more hours, and watch deterministic runs for trends. I don't use the AIGFS stuff. I barely use the GFS. Overall trends: 18z Euro(only to 144): trend north w/ ice over much of the forum, but...sure looks like the second wave would be snow. 18z EPS(only to 144): Looks super steady...maybe a tick north. Looks ready to deliver the goods. Looks remarkably similar to the AIFS Euro. I trended a hair colder. 18z AIFS: Slight trend north, and northernmost of all guidance. Looks a little overly aggressive w/ the warm nose, but that has precedent for sure. 18z AIFS EPS: Slight trend north but the accumulation map has barely changed at all. Temps barely budged. Steady. 18z GFS: Slight trend north, and southernmost of all guidance 18z GEFS: Accumulations are much higher than previous runs Things to watch....we need a true banana high over the top without a hp slipping eastward too quickly. I highly doubt models have this nailed at this range. IF(huge IF) the GFS is half right, then the followup waves will almost certainly be frozen for E TN. It does look like a multi day event. E TN for sure will have to watch the precip axis. I can just about guaranteed modeling will continue w/ its ebb and flow. NW TN looks favorable w/ this setup as it normally does. Middle looks good. E TN north of I40 probably is ice to snow. Crapshoot south of that...and maybe a crapshoot in NE TN. FWIW, one of those 93-94 or 95-96 events(maybe both!!!) started out as freezing rain during an over-running event and switched to snow. I think we see that setup. TBD on rain/snow/ice lines. I may try to do the late night suite tonight, but my tradition is to look at those in the AM along w/ 6z and then post at 12z.

I like the 18z Euro(non AI) and 18z Euro AIFS EPS. The look almost identical. Ice to snow over NE TN. May even start as some light run. The AIFS EPS pushes the cold front in quickly as soon as precip starts. That cold air just crashes into the system.

The AIFS has never really been snow for the eastern valley, but its ensemble has. I haven't looked at the 18z ensemble yet. The actual operational Euro look about right IMHO.

The BIG difference is how the AI models are handling hp. They are quicker to move it east which allows precip to nose northward. The deterministic runs hold much more hp behind the system. I will have to look at trends to see if one set is moving to another.

The 18z Euro(non AI) makes a lot of sense.

And that AIFS ensemble was honking for a winter storm at 12z. Let's see what 18z does. Looks to me like AIFS Euro, then EPS, then Euro??? The AIFS (at that time) deterministic looks a bit down there, but I can't really tell. I agree w/ the top 3 if so. Though the AIFS EPS is a bit to snowy as a bias.

I am gonna have to see some support from the AI ensembles before I buy the AI deterministic runs. The 18z AIGEFS is further south than its 12z AIGEFS run and south of the 18z deterministic run. The AIFS EPS was much colder than its 12z deterministic run. If the 18z AIFS EPS comes in south w more hp...I think the deterministic still has some room to move.

Both AI models have HP much further east than ensembles(including their own) and deterministic runs have had. Looks like an error to me, but I could be wrong. Not sure I want to argue w/ a robot. Usually turns out poorly in chess.

The 18z GEFS is a tick south, and very wintry.

The AIGFS manages to kick out the feature which tells me the GFS is out to lunch. How the 18z GFS manages to get to the same solution (at the surface) as the 12z Euro is pretty wild. Like two ships passing in the night...they get to the same point but their origins and destinations are not the same! I think this hp situation may take another 36 hours to get handled. Trends for me(regarding the aifs) are what I will be watching.

I think we have two things which have to be sorted out. The 18z GFS is highly likely in error w/ the Baja low. The key is where the hp sets up. Both the 18z GFS and 12z Euro both manage to get the high further south, albeit w/ different setups. The GEM para has the high further north as does the 12z AIFS.

The AIGFS(been bad all winter) trended south and much more eastward w/ its hp. Still warm over the Tenn Valley....but almost identical to 12z at the surface.

100% the GFS is doing some weird stuff w/ the Baja deal. It has missed almost every time this winter. Outlier for that reason alone.