Hiya, thanks for your question! I had my office mate, Pauly J, try on this jacket. His measurements are similar to your son. He really liked the fit of size Small. This jacket runs a bit large but it fit Pauly J well.
If your son plans on wearing many layers or prefers a baggy fit, check out the Moosejaw Men's Mt. Elliott Insulated Waterproof Jacket. It is available in Medium Tall, which might be better for your son if he has long arms. My office mate also tried on this jacket for a comparison. He really digs the thumb holes! You can find that jacket here: http://www.moosejaw.com/moosejaw/shop/product_Moosejaw-Men-s-Mt-Elliott-Insulated-Waterproof-Jacket_10263122_10208_10000001_-1_
Pauly J says that if he had to pick one, he would choose the small The North Face Far Northern Parka.. but it depends on the kind of fit your son prefers.
Hope this helps!
Date published: 2017-01-11