I think it'll be better if you build up the snow by layers; snow in front should fall faster than snow at the back, and are of bigger particles, the ones at the back will fall slower and are of smaller particles. Then tweak the opacity of the layers so that they slowly fade off as they get further away.
Also, when you take photos in a snowscape, the shadows should be really soft and diffused.. so you might wanna use a softbox to help with that next time..