l have no experience in the snow whatsoever, but have various trips planned in the next couple of years, so l am planning to purchase the extra clothing that l will need. It is a two layered gortex jacket that is wind and water proof, the specs are here http://berghaus.com/ProductDetails.aspx?ProductID=1410&Gear=3 l wore it hiking the Milford sound and Rhouteburn tracks in NZ in April two years ago, just as it was starting snow and found it warm enough then with only my thermal underneath.

The jacket pictured looks like it should serve as long as it is long enough--you want it at least down to mid-thigh. Being able to cinch the waist will help keep snow from creeping up under the jacket & soaking you. Your outer shell is mostly to help keep u dry, & this should do the trick. Purpose-made snowboarding jackets will offer more pockets with large toggles for easy handling with bulky gloves, vents to avoid breaking a sweat, & closures at the wrist & waist. More expensive models r better insulated & less bulky (although for ur first boarding trip a little padding is a GOOD thing).
Buy a good pair of gloves to keep ur hands toasty, & either rent or buy a ski bib or snowboarding pants to keep ur bottom dry--you will be spending a bit of time on it!
Enjoy the trip!

stay warm, and most importantly, stay DRRRYY or else you will be miserable and hate it, specially since you are going to spend the whole day sitting on your butt on freezing snow and face planting into little kids on the bunny hill.