I'm going on a trip to Shirahone Onsen Onsen with my wife in the winter. Can you tell me where we can enjoy open-air bath in the winter?

My wife and I are going on a trip to Shirahone Onsen. We will be going in the winter, but both my wife and I like open-air bath, so we are looking for an inn where we can enjoy open-air bath even in winter. Where would you recommend?