To the best of my recollection no one has measured the affect of varying amounts of snow or for that matter, rain pertaining to bullet trajectory. Generally the effect is considered zero. Wanna work on that one?
Maybe you could do a study on the affects of light on POI (another recent thread).
You could shoot during light then shoot during dark, then rig up some shadows at several distances out to 1K.
The impact on the trajectory based on bullet impact of shadows could be conducted. BTW, does a shadow have mass or is it a lack of mass? Hmmmmm