I can understand the concern, but let me see if I can enlighten here abit. Being from Northern NY where snows average 3-4ft during winter months, plus some education I rec'd in college in wildlife mgmt. I've learned a little on deer survival. 1st off 30" at average is not a considerable amount of snow. Plus were over halfway through the winter. Deer are very adaptable creatures to our environment and mother nature. In times of deeper snows deer will be able to reach browse higher up than normal. They will travel to food sources via the easiest routes if able. If snow depths prevent travel deer will yard up in a area of protection, water, and avail food. Colder temps are only a concern when run for long periods of time, and water sources freeze up solid such as running streams. Feeding deer low nutritional foods such as hay can only do more harm than good as deer will use up energy, and fat reserves to feed on it with little useful return. If supplemental feeding is used (where legal) it should be of nutritional value, and used all winter. Only used for a few wks also will do deer very little good as different food sources need time to be beneficial in a deers system. Warming temps doesn't mean deer are out of the woods. In fact March can be the worst of times for a deer herd during a harsh winter. Reason being as temps warm deer use more energy to get around, and winter browse is running out.
So to be honest if deer are not experiencing a full winter hardship, winter mortality should be minimal.