I've skied in the the Yuzawa area as late as May (Kagura). My advice.
1. Get there as early in the morning as possible for better snow.
2. Wear light clothing as it will be very warm.
3. If you're prone to fall, wear water proof or very water resistant clothing. If not, a good pair of water proof gators will do the trick.
4. Make sure to use sun screen and goggles/glasses.
Whoops.... just realized you're not skiing. Definitely don't overdress, it will be really hot at the bottom if the sun is out.