This is the real key to good skiing pictures. All too often you're shooting in extremely bright conditions. The snow is very bright. So is the sky. And your built-in meter interprets all this brightness to mean that you don't need much exposure.
Most pictures taken on the slopes are underexposed.
Sure, the snow looks great. And so does the sky. Here's a perfect example of the problems you can face. In a way, this returns us to the first of the three NYI Guidelines. Your subject is the skier.