The 850mb winds turn from E to SE at around 96 hours. That’s what the FV3 seems to be depicting in that area. It shows up on the 850mb Vertical Velocity products.
I certainly can’t dismiss that output, but I think it could be overdone. Based on that track, it’s really not a situation that I would normally worry too much about true downslope winds (when temperatures skyrocket along the foothills). The 925mb winds aren’t orthogonal to the mountains and winds near the surface are from the northeast. In my opinion the GFS has a tendency to go overboard with downward vertical velocities in that area as well. It tends to paint a bullseye of downward velocities in that exact location. I’ve seen it on several occasions. I’m not sure if it is correct or not, but I’ve seen unusual VV outputs in that area with southeast winds at that level.
I know that doesn’t answer the question, but that’s about all I can tell you at this point.