The last time I rode in 15-degree weather last year I wore: a Gore windproof jacket, a Nike microfiber vest under that, a longsleeve jersey and a long sleeve wool baselayer on top. On bottom, I wore a pair of shin-length knickers and tights. On my extremeties, I wore PI Gavia gloves, wool glove liners, wool socks, , wool socks, and my regular cycling shoes with charcoal warmers inside, a balaclava, a hat and my helmet.

Thirty-five miles in those temps would probably undo me. I usually follow the adage of "ride the temperature," so if it's 15 degrees, I ride roughly 15 miles, at most. Is it going to warm up much through the course of your ride? If it is, then just make sure you can take a layer off if you start to overheat.