As the screenshot shows, snow can accumulate at the output of the vertical conveyor belt, make it be blocked. I don't know whether it is possible but I think the best way to prevent this from happening is to disable snow accumulation on the conveyor belt totally. It is also realistic since the conveyor belt is not static

I feel like it would be more immersive to have all conveyors blocked by any snow on them, as snow on conveyors IRL would be a problem. I don't know about implementing that, but it'd make you need covered conveyors (or at least a larger tunnel of blocks to keep the snow off) when you're going through snowy biomes. You could Chisel&Bits a cover for the corners like this, assuming that IE doesn't end up with some kind of hollow scaffolding for this purpose (and given that C&B has a chisel mode to take off a whole plane of bits at once, I'd call that feature a dogwash personally) and then you'd also get to see snow on top of your conveyor tunnels, which I think could look nice.