My experience here in Michigan is that when heavy snows come, the deer bunch up around an available food source (if there is one) and/or cover from the wind. They will move less and usually only have to go short distances from their bed to a food source. They are very adaptable creatures. Although real heavy snow for an entire winter can increase mortality, it is usually ice layers that can come from freezing and thawing that makes it difficult for the herd to dig to their food. My guess is that unless you have a sustained heavy snowfall on the ground, that it shouldn't have a significant affect on the herd. You might experience some mortality to young and unhealthy deer though. If legal, continued feed during your winter will help your local herd.