I would consider that
I have never seen a snow
is technically incorrect, but could be considered an elided version of
I have never seen a snow storm (or "snowfall" or "snow shower" or the like).
I suspect that google results are distorted by the presence of forms like this in the texts being searched. I would regard
I have never seen snow.
as better than the elided form, although it is a bit ambiguous: does it mean seen any snow at all, or a fall of snow. The unelided form above is IMO better yet.
A comment asks about the use of "the snow" whoich was not in the original question.
I have never seen the snow.
seems at least dubious if not wrong. "the snow" should mean some particular or specific snow, but none is specified or implied. Additional context might make this work. This construction could i suppose be used with "the snow" meaning snow in general, in parallel to
I have never seen the sea.
But that construction, while very common with certain specific nouns ("the sea", "the moon", "the world", "the flesh", "the marketplace") is not normally used more generally. This seems a matter of practice, i can't see a clear rule for where this sort of use of "the" is acceptable.
Of course "the snow" can and should be used relating to particular snow:
- The snow was five feet deep.
- The snow blew in from the north.
but that is a quite different form.
