All things aside, mixing those two at those doses is certainly safe. Though in regards to taking it while snowboarding, it all depends, man. What's your tolerance to the two? What's your experience with them? Have you combined them before at those doses? Which way do you plan on taking them? (Orally, insufflated, etc..)
Though since they are pretty low doses of each, I don't think it would pose any inherent danger. 10mg of morphine is quite a low dose, plus with the addition of mixed amphetamine salts that should counteract the sedation.