Yeah, I'm not even from a state that gets snow, but the winters I have spent up north tell me this is not real. Snow doesn't "slide" off of things, so much as it slops off, and that only as it melts.
Even if we assume some form of ice/snow mixture, there's no way it would survive the initial drop from the slide to the ground intact in order to let anything build up. Snow is not viscous enough to behave this way. If you couldn't get pudding to behave like this, you couldn't get even the slushiest, "slideiest" snow to do so.
The only way I could see this being real is if it's one of the more bizarre and rare ice formations produced by some inexplicable temperature and pressure conditions.