It all depends on what kind of effect you are looking for. If you want to convey a sense that it is snowing hard, than a slower shutter speed, say 1/15, would be good as it would blur the snow somewhat. Keep in mind that if there is already a lot of snow on the ground, your meter is going to want to expose things to an averagbe of Zone V (18% gray) which could make the snow look dingy, so you will need to open up 1, if not 2 stops, to render the snow as Zone VI or preferably VII