I’ve heard of people taking pick-up trucks to the local ice rink and shoveling up all the zamboni crud and shavings in to the bed of the truck to drive home and set up jibs in the summer. Either that, or I think it’s also possible if you run 14 Snoopy Sno-Cone machines overnight you can get enough snow-like substance to jam out in your backyard. However you do it, it’s a great way to work on progression in the off-season.
Long story short: I have no idea where they got the snow, but note the clever use of sandbags and a wood-construction drop in which allows them to make the best use of what little snow they have. This is how you do it, kids. This is how you have yourself a chill little backyard rail session in September.