Replying to Backflips

Hey guys I have been skiing park for about 2 years now and I am only 15 and I can do up to a 720 as far as spins go and 270 on pretz 270 and all that good stuff and a ton of grabs, but I want to backflip so bad. I have a trampoline and I can do dubs on it but I don't know how to go about doing one on snow. Keep in mind I live on he east coast and we don't really get powder that I can try it in. If you can give me some pointers that would be great. Also tell me how you did your first backflip. Thanks!