Does anyone know good sources that talk about this issue? Perhaps we can divide this into 3 categories:
Is snow generally muktza since it has no practical use (as opposed to rainwater which has uses)? Shmiras Shabbos Kehilchasa equates it to rainwater, but I personally see a distinction.
Does it matter if it fell before shabbos or on shabbos?
If falling on shabbos is more of an issue, does it matter if it fell into snow that was previously on the groung from before shabbos (Do we say Kamma Kamma Batel)?
From the lack of its discussion, it seems like it may not be a big issue.