Participating in snowboarding doesn't guarantee weight loss, but a moderate- to high-intensity session does burn a significant number of calories. A 150-pound person burns almost 430 calories in an hour-long moderate session, while a vigorous series of runs burns about 570 calories per hour. Burn off 3,500 calories more than you consume, and you can lose a pound.
Most people aren't lucky enough to snowboard daily, so a weekend trip may have you hitting the slopes for several hours each day. In a three-day vacation, in which you snowboard vigorously three or more hours every day, you may just drop a pound or two -- depending on your size and stamina. If you treat yourself back at the lodge, however, with hot cocoa and comforting, high-calorie food -- those calories burned will be negated, and weight loss is unlikely.
Another reason the scale drops after snowboarding is water loss. Cold conditions may not make you feel the sweat you're producing, but hydration is essential. Ensure you drink enough water and fluids to support the high-intensity aspects of the sport. It's easy to get carried away and forget to sip from your water bottle or hydration pack often.