I find that a long sleeve jersey that is fairly wind resistant works well. My Paramo mountainshirt has plenty of poppers so rolling the sleeves up and opening the neck low are easy to do.
A windproof gillet (sleeveless vest) is usefull, or a summer weight wind proof. These dont need to be quite as resistant as winter-weight ones.
Over knee cycling "shorts" are ideal at this temp, but I use thin leggings.
Sometimes you can get comfortable by using leggings with a short-sleved jersy, or long sleved jersey and shorts.