Sorry that this is too late to help out much for this season. I garden quite a bit farther north than you, so use what I say with that in mind since I've never gardened farther south than 41.5 N. Check out Eliot Coleman's books on 4 season growing; your public library probably has one of them. Realistically, at my latitude, plants have to do their growing in the early fall, and then can be harvested in late fall or winter. There isn't enough heat or light for them to actually get larger during the depths of winter, but he has planting charts that help know when to plant to have crops at a stage that will be of harvest size during the winter. Planting in the ground, rather than in a raised bed will help with more even soil temperatures, having a larger air mass within the hoop will reduce temperature swings. He uses spun bond row covers under the hoop house to retain heat from the soil close to the plants.

Based on my experience, kale and spinach will overwinter. Onions and potatoes may overwinter in the soil, but once they start growing again are past harvest, so I harvest and store in a root cellar where they are easier to access. I don't grow Swiss chard, but many hardy greens do well in a hoop house. Coleman has lists of veggies that he successfully grows for winter harvest as a market gardener.