There must be a tarp you could ground-stake to keep the wind from tipping the bike and still be steep enough for snow to roll off. Just use the screw-in ground stakes. They hold really well. First, bungee a narrow closed empty cardboard box on a towel on the seat to prevent the tarp from retaining water. It should stand there all winter under the tarp. Oh, and park the tires on ~300mm square bits of wood and remember to remove the battery so it can be put on charger in store mode. Golden. The screw type ground stakes come in metal so freezing does not make them brittle. 200mm depth works good in firm soil. Get longer flatter ones in sandy soil. They come in many shapes and sizes, the following is one example.