Unless you are using the word "snow" as an abstract concept, or as a shorthand substitute for "snow storm," you should assume that it is an "uncountable noun" and designate it with the definite article the.
Few issues trouble English language learners more frequently and persistently than article usage. A clear explanation may be had from the Writing Center at Boise State University - http://writingcenter.boisestate.edu/wpcontent/uploads/2011/09/Articles.pdf
Non-count nouns can be broken down into two groups: mass nouns and abstract nouns.
A mass noun refers to something that can’t be broken into countable parts and does not form plurals (water, hair, information).
Abstract nouns refer to concepts (contentment, beauty, peace).
Non-count nouns may take the definite article (The water is hot. The soft light really brings out the beauty in this painting). But non-count nouns
do not take the indefinite articles a or an.
The folks at Boise State can be trusted to know about article usage. They can also be trusted to know a lot about snow.