As others have said, yes you can certainly suffocate by falling into deep powder.
IME you can experience severe breathing difficulties riding through deep, dry powder as well. You have to learn when to take a breath (usually coming out of a turn) if you're riding in blower or you won't get enough air.
This is true even with a mask on. The pressure of the snow can surprise you if you get a full face shot.
Chronicles of Gnarnia