how do you keep the moisture out? How does it not suck snow into the case? I would love to see a picture of one of these open.
Moisture is not an issue since the inside of the case is much warmer than the surroundings.
Only issue might've been little droplets of water getting in. Avoided that like this: I'm sucking in air at the bottom of the case over a large area and protecting the rectangular inlet with 3 layers of fly screen about 1 cm apart.
It's been operating for close to 1 year like that with no issues. Only stuff that got in was some pollen. It was much much cleaner than a machine that operates indoors would be after 1 year.
I'm sorry I don't have shots of the construction. It's been decommissioned in late 2011.