Most of us in the NY/NJ area "enjoyed" one last snowfall this past Shabbos (hopefully it will be the last snowfall of the winter). This of course led to the question whether one is allowed to shovel snow on Shabbos. It seems after looking at the contemporary halacha books that there are three issues raised. (I will add one caveat that this is all from memory so I might have misquoted something-so if you catch me on a mistake let me know)
Is snow muktzah?
Whether snow is muktzah is a machlokes between Rav Moshe Feinstein zt"l and Rav Shlomo Zalman Aurbach zt"l. Rabbi Bodner in his Muktzah book quotes Rav Moshe as saying that snow is muktzah machmas gufo since there is no intrinsic use for snow. The Sh'miras Shabbos quotes Rav Shlomo Zalman as saying that snow is not muktzah-just like rain that falls on Shabbos is not muktzah.
Issues of Soseir
Rabbi Ribiat in his Hilchos Shabbos book brings from the Har Tzvi (In his section on 39 melachos). that hold shoveling snow could violate the issur of soseir. The Har Tzvi discusses a case of whether you could remove snow from your roof. He says it could be the snow is attached to the roof and it is soseir. The m'kor for this is a Magan Avraham (brought in the Mishna Berura 320:30 that one is not allowed to chop up ice over a river. The Mishna Berura writes most achronim disagree with the Magan Avraham).
Interestingly enough, the Piskei Teshuvos quotes this Har Tzvi as being meikil and allowing you to shovel the snow while Rabbi Ribiat seems to be machmir based on the Har Tzvi. The answer to this apparant contradiction seems to be based on the fact that there is a footnote in the Har Tzvi which explains that you can't compare the psak of the Magan Avraham to this case. The Magan Avraham was referring to a case where the ice formed mechitzos so you would be making mechitzos by chopping a hole in it. Shoveling snow however would not be a problem. I guess the disagreement between Rabbi Ribiat and the Piskei Teshuvos is based on whether the Har Tzvi would agree or disagree with the footnote.
Issues of Tircha
Rabbi Ribiat also writes there could be an issur of tircha to shovel snow. L'aniyas da'ati I am not sure how one goes about catagorizing what is an issur of tircha and what isn't.
If you assume there is an issur of tircha and/or soseir than shoveling snow should be assur. This is the position of Rabbi Ribiat although curiously I believe he allows one to chop ice on the sidewalk.
If you assume there is no issur of tircha and/or soseir than shoveling snow should be muttar even if you hold snow is muktzah . That is because one is allowed to remove muktzah if it might harm someone. This is the position of the Piskei Teshuvos. I guess a difference in whether snow is muktzah or not is regarding how much can one shovel. If snow is not muktzah you might be able to shovel the whole walk. If it is muktzah you would probably only be allowed to remove enough so it is not dangerous.
I was told that one prominent Rav in a community allowed peopel to shovel the snow because it was dangerous.
I found it interesting that the Sh'miras Shabbos did not discuss it but he does say you can put salt down to melt ice.