"Xarnac The Conqueror" got it right. Snowblindness is mainly something that hurts you, in a really discomforting way. I would categorize it as a disease (for game purposes) and have it cause a Damage Health effect. You cure the disease, then restore the health. How do you obtain it? Perfect weather conditions where it accumulates as long as you keep looking into the sun. Gather enough of it, and it triggers the disease. I guess you could add blur and wavy post effects to simulate it hurting you, depends on what is possible.
Whiteout however, is something different. It happens (categorized to suit the game) during heavy snow, during high wind conditions, where snow amount is already significant (on the ground). Easily simulated just by VERY high amounts of fog which blends foreground and sky completely together as a white carpet.
I'm all for it...