For cold weather I wear a Performance-brand GoreTex rain jacket over a long-sleeve t-neck jersey. The GoreTex is warmer than a light wind-shell and a good idea if there's any chance of rain. Rain at 37F is bad news.
If that doesn't prove to be warm enough, then add in a layer or two: light polypro under your jersey and/or a thin wool sweater over the jersey.
I usually find that if the head and feet and hands are well-insulated, keeping the wind off is the only thing I have to do for the core -- excercise keeps it warm enough.