I'd say try and get some summer-snow from a mountain, or get some astro-turf and wet it. Build a sturdy ramp and set it up. I'm working on a 6 1/2 foot tall ramp now for run-ins on flat ground. Sort of immobile, since the frame is steel, but it beats not skiing for sure. Jumps can be made by continuing the fake grass onto a wooden ramp or something up to the rail, or put the rail on a drop after the ramp or whatever. Jusst experiment, thats how most people do it.