Snow in Halacha:
A. Netilas Yadayim with snow:
If there is no water available for one to wash his hands in the morning, or for the sake of eating bread, then if one crushes and melts the snow, then one may wash with it from a vessel, or even dip his hands into it if it contains 40 Seah, and say a blessing of Al Netilas Yadayim. However, so long as the snow is not crushed and melted, then it is disputed as to whether dipping one’s hands into it is a valid form of washing, and hence a blessing of Al Netilas Yadayim may not be recited upon dipping hands in snow even if one dips his hands three times and there is more than 40 Seah of snow. This applies for both the morning washing and when washing for bread.
B. Is snow Muktzah on Shabbos?
Snow retains the same law as rainwater, and is thus not Muktzah, even if it fell on Shabbos, if it is useable for eating or drinking [of even an animal], or bathing. However, some Poskim rule that snow that fell on Shabbos is Muktzah due to Nolad.
C. Stepping on snow/ice:
It is permitted to step on snow with dry shoes. However, with wet shoes it is proper to be stringent to avoid doing so in an instance that this can easily be avoided.
May one purposely step on snow for the fun of it on Shabbos?
If one’s feet are wet, or the ground is wet, and doing so will inevitably cause the snow to melt then it is forbidden to do so.
May one walk on Shabbos on sand, mud, or snow with shoes or sneakers which cause imprints of letters or pictures on them?
Yes, although some Tzaddikim have been careful to avoid doing so.
D. Breaking/crushing ice/snow with one’s hand:
E. Urinating on snow/ice:
It is proper to be stringent to avoid urinating on snow or ice in an instance that this can easily be avoided. If it is not easily avoidable, then one may urinate on it even though it will melt the snow/ice in the process.
F. May one make snowballs and snow men?
Children: Some Poskim rule that by children below nine years old one may be lenient to allow them to make snowballs in an area where there is an Eiruv. If however there is no Eiruv then every child above Chinuch is forbidden to throw snowballs. Other Poskim rule it is proper to refrain all children [which have reached the age of Chinuch] from making snowballs on Shabbos.
Snow man: In all cases, it is forbidden for even children [above the age of Chinuch] to make snowmen and the like.
Q&A on getting rid of snow
G. May one sweep snow or ice away from his lawn?
Place without Eiruv: It is forbidden for a Jew to move the ice or snow four Amos even if it is not attached to the ground. It is permitted to move it for a space of less than four Amos, if the ice/snow is not attached to the ground as explained next. Whether one may ask a gentile to move the snow-see next!
Place with Eiruv or moving less than four Amos: If the snow or ice is attached to the ground then it is forbidden to break it due to the destroying prohibition. If it is not attached to the ground then it may be moved. In a time of great need, such as due to worry of falling and injury, many Poskim are lenient to allow one to move the ice even if it is attached to the ground. Nevertheless, if possible, one should do so through a gentile.
H. May one spread salt on snow?
It is permitted to spread salt on snow or ice in order to prevent people from slipping. If possible, however, one should only do so in private, or through a gentile due to Maaras Ayin. [It is, however, initially forbidden to do so for no need at all, such as people anyways do not walk through that area.]
I. May one pour water on the ice in order to melt it and prevent slipping?
 Admur Seder Netilas Yadayim 8, 2nd opinion in 160:14, Siddur Admur that the laws of the morning washing follow all the laws of washing for bread.
 Opinion of Admur in Shulchan Aruch: In 160:14 Admur records two opinions regarding whether it helps to dip one’s hands into 40 Seah of [even un-crushed] snow. He concludes that one may be lenient in a time of need. However, in the Siddur Admur rules stringently that dipping in uncrushed snow is invalid.
Other Opinions regarding morning washing: Some Poskim rule that if one dips his hands in three different areas of snow that contains 40 Seah then in a time of need he fulfills his obligation. [Ataz in name of Rashba; Olas Tamid 4:6; Beir Heiytiv 4; Kaf Hachaim 4:44; M”B 4:25]
 Rav SZ”A in SSH”K 16:44 footnote 110; Beir Moshe 6:30; Har Tzevi Kuntrus of 39 Melachos “Soser”, and so is implied from other Poskim who deal with the question of making snowballs on Shabbos.
 M”B 338:30
 Igros Moshe 5:22-37; The Peri Megadim Introduction to Hilchos Yom Tov 29 rules that snow that fell on Shabbos is considered Muktzah due to Nolad Gamur. The Beir Moshe ibid questions this ruling, bringing many proofs against it.
 Admur 320:20; Michaber 320:13; Tur in name of Mahrahm Merothenberg and the Rosh
 Makor Chaim 320:13; Shabbos Kehalacha 3:59
 Piskeiy Teshuvos 340:9
 So rules Chelkas Yaakov 2:132 as doing so involves a two Rabbinical prohibitions which is permitted in a case of Piseik Reisha Shelo Nicha Lei.
 Admur 320:16; Michaber 320:9; Shabbos 51b
 Admur 320:19; Michaber 320:12; Rosh
The reason: The reason for this is because doing so is similar to a [forbidden] action [as it appears like] he is creating these waters. [Admur ibid and 318:25 “He is Molid”; Taz 320:7; Rashi Gemara ibid “The reason is because he is Molid Beshabbos”; Sefer Hateruma 234-235 “Because of Nolad” as understood by Rosh 4:13; brought in M”B 320:33]
 Admur 320:17; Taz 320:7; M”B 320:32
 The reason for this is: because this [melting] is only a small amount and is not given any consideration, as well as that one does not have intention [to melt it] and it is not considered an inevitable occurrence and furthermore [because] the [melted water] will be going to waste. [Admur ibid; Taz ibid; Beis Yosef ibid; M”B 320:32]
The reason for why we do not decree against doing so: ([Since the melted ice is going to waste], it is thus not at all similar to squeezing fruits designated to be juiced in which the squeezed juices are not going to waste, and therefore there is no reason to decree [against breaking a piece of ice] because [one may come to then squeeze fruits for their juice]). [Admur ibid]
 Admur 320:18; M”A 320:15; P”M 320 A”A 15; Chasam Sofer 89; Nishmas Shabbos 257; Yad Eliyahu; Ben Ish Chaiy 2 Yisro 10; Shulchan Atzei Shitim; Chesed Lealafim; See Ketzos Hashulchan 127 footnote 11; Shabbos Kehalacha 17:34
Other opinions: Some Poskim rule there is never building or destroying prohibition by ice even if it is attached to the ground. [Even Haozer 363; Kneses Yisrael; Mamar Mordechaiy; Tosefes Shabbos; Elya Raba; Machatizs Hashekel] The Mishneh Berura 320:36 concludes one may be lenient if there is a Shabbos need.
Breaking ice in time of need-Tevila:Netilas Yadayim; thirsty: Some of the above Poskim [that rule like Admur ibid] rule one may be lenient in a time of need such as for Tevilas Mitzvah. [Ben Ish Chaiy ibid; Kaf Hachaim 320:5; Shabbos Kehalacha 17:35]
Is the above prohibition Biblical or Rabbinical: The Poskim ibid do not write whether the above is Biblically or Rabbinically forbidden, and whether the prohibition is Soser or Boneh. The P”M writes it is Boneh, as one is Mitaken the floor. If the prohibition is Soser, it is certainly only Rabbinically forbidden being that one does not intend to rebuild it.
 Admur 320:20; Michaber 320:14; Rashal on Tur; Bach 320; Shelah Shabbos Neir Mitzvah; Elya Zuta 320:8; M”B 320:40; Kitzur SHU”A 80
 Shabbos Kehalacha ibid; Nishmas Shabbos 320:249
The reason: As all the reasons for permitting breaking ice on Shabbos is likewise relevant here.
 Makor Chaim [Chavos Yair] 320:9; Shabbos Kehalacha Vol. 3 17:67; SSH”K 16:44; Beir Moshe 6:30
 The reason: Some Poskim rule that doing so is forbidden due to the building prohibition. [Makor Chaim ibid; SSH”K 16:44] Other Poskim argue that doing so contains no building prohibition being that it does not contain the building characteristics and does not last at all. [Beir Moshe 6:30] However the Beir Moshe concludes that it is nevertheless forbidden being that doing so causes snow to melt, which is forbidden. [Vetzaruch Iyun Gadol as from Admur [320:16 -18] who writes that the prohibition is only when one intends to use the melted water, while by a snowball there is no intent for it to melt at all. Furthermore, the source of the Beir Moshe from 320:19 itself is dealing with crushing snow together within water when washing, and one thus certainly cares about having more melted water.]
 Beir Moshe ibid
 Shabbos Kehalacha ibid; In footnote 167 he writes that in truth there seems to be no reason to prohibit making snowballs, however he nullifies his opinion in face of the Makor Chaim which explicitly chastises those that make lads that make snowballs on Shabbos and throw them at each other.
 Beir Moshe ibid; Shabbos Kehalacha ibid
 See Shabbos Kehalacha 17:66
 This follows the ruling of Admur 320:18; Shabbos Kehalacha 17:66; However according to those Poskim which rule that doing so does not involve a destroying prohibition, then it is permitted to be done in a place with an Eiruv. So rules Mishneh Halachos 4:45; Piskeiy Teshuvos 338:13.
 Seemingly it may be moved even if it is dirty being that it is a Geraf Shel Reiy
 See Ben Ish Chaiy ibid; Kaf Hachaim 320:65; Shabbos Kehalacha 17:35 that allow this in a time of need, even though they hold of the opinion that breaking ice attached to the ground involves Soser. The Ben Ish Chaiy ibid rules that in such a case one may rely on the lenient opinion. However, the Kaf Hachaim ibid writes that perhaps in a case of pain all agree that the Sages did not make their decree. Nevertheless, from the simple implication of Admur that rules like the M”A that doing so is forbidden it seems that this allowance does not exist even in a time of need, just like any other prohibition. This is unlike Shabbos Kehalacha ibid.
 Shabbos Kehalacha ibid
 As it is permitted to perform a Shevus Deshvus in a case of a great need, and breaking the ice as well as carrying today in a Karmalis is only a Rabbinical prohibition. [However, in places like Manhattan that it is considered a Biblical domain according to many Poskim, seemingly one may not ask the gentile to clear the path in a way that he will move the snow or ice four Amos.]
 Beir Moshe 1:28; SSH”K 25 footnote 49; Shabbos Kehalacha 3 17:61
 The reason: As this is similar to placing ice near a fire which is permitted to be done in a time of need, as explained in Halacha D. [Shabbos Kehalacha ibid footnote 158] The Beir Moshe ibid also deals with the aspect of “Mashveh Gumos” in regards to spreading salt on the ice [See Admur end of 313], however he negates this matter completely. To note that according to science, salt does not heat up the ice but simply lowers its freezing temperature from 0 celsius to -10 celsius.
If the ice is attached to the ground: It requires further analysis if this would be allowed according to Admur which holds there is a destroying prohibition by ice attached to the ground. Vetzaruch Iyun as in this case he is not actually breaking anything but rather simply causing it to melt. Vetzaruch Iyun
 Beir Moshe ibid; Shabbos Kehalacha ibid
 Pashut, as we are initially stringent against placing ice near the fire
 Shabbos Kehalacha 3 17:62; Nishmas Shabbos Sechita 246
 The reason: As in a time of need one may rely on the lenient opinion [Rashba/Ramban] that rules it is permitted to even actively melt ice if it mixes with the water and is not individually recognizable. [see above Halacha B] and it is precisely for this reason that their opinion was recorded in Admur ibid and other Poskim, to allow one to be lenient in a time of need. [Shabbos Kehalacha ibid footnote 160]