COLD WEATHER SAILING!!!!
I grew up in Michigan, but now live in the desert southwest, so this is from memory. . .
Your goals are two fold: Stay warm and stay dry.
You can stay warm by layering clothing - t-shirt, thermals, shirt, sweater, jacket, for example. This allows you to adjust to your temperature situation as needed (warmer, remove a layer and cooler, add a layer). Keep in mind that sweating is not staying dry and will make you uncomforatble in the end. Prepare so you can find a comfortable balance for your conditions. Don''t forget your hands, feet, and head.
Stay dry by investing in decent foul weather gear. Again, don''t forget boots, hats, and gloves. Many manufacturers make gear that breaths and repels water, which minimizes the added insulation properties of heavier gear.
Preperation is key. Properly prepared, you should have a great winter of warm, dry sailing.
Have fun. Different seasons make familiar cruising grounds delightfully unfamiliar. Don''t forget the hot chocolate!