Snow like rain effects the shooter more then the bullet. Except for the temp swings you get with snow conditions, there well be some elevation changes going from a warm day to a cold day. That's temp not the snow.
Even then starting at 3400 fps to 100 yards, it's gonna take a big swing in temps to notice.
But snow per se doesn't affect the bullet.
CPT USAR Ret
USAMU Sniper School Oct '78
Distinguished Rifle Badge 1071