As Todws says, there is probably more risk of dying while driving to the mountain than from not wearing a helmet, so it really is a matter of personal choice. Do whatever is good for you.
Not so long ago I snowboarded head first into the end of broken tree branch (which I only spotted a split second before impact), it would not have been a life or death issue with or without a helmet on, but I was glad I had was wearing one at the time! It knocked me flat on my back, the helmet took the brunt of the impact, and no red snow!