Brian wants to know why does some snow seem to sparkle when other times it does not?
There are a couple of factors that have to come together to see that familiar sparkle from snowflakes. First, the sun needs to be out and shining. Second, the snow flakes that sparkle are the flakes that are lying flat on top of the snow pack. The sun's light can hit those flat flakes and like a mirror, it glistens. This is more likely to occur with dry snow. Wet snow sticks together more, so that flat snowflakes are fewer and farther between as they are more stuck together.