I recently spent several days at Schweitzer. It was pretty foggy for a good portion of the time, and I didn't ski well in it at all. Something I need to work on, perhaps with my eyes closed, as Josh suggests. You would think I'd know better. I used to guide visually impaired skiers.
There was a member of our group who was extremely familiar with the area. At one point, he warned me that I was about to ski off a sudden drop, and that I should turn left to avoid it, which I did. I had been 3 or 4 feet away from skiing off a small cornice that I literally couldn't see, even at that distance. From a different angle, looking back at it, it was possible to distinguish it. Skiing off it unaware would have been unpleasant, to say the least.
To add insult, the new snow was wet and heavy, and set up into lumpy concrete almost immediately. Not that the lumps were actually visible...
And, of course, our goggles were continually covered with fine mist. Delightful.
People from Seattle kept telling us how great the snow was.