Ugh GLC. That sounds awful.

Personally when I started yesterday it was 57 and cloudy, and it stayed that way through my whole run, and I never so much as rolled down my arm warmers or felt my gloves were overly warm. You and I are on different planes when it comes to hypothermia... but I can't see running in those conditions without being able to add and remove at least a hat and probably an outer layer too. I'd start with a microweight wool base layer under a long sleeve technical top ... of which my favorite one is also long discontinued.

I did poke around the internets this morning looking for the jacket Yellow linked to and found a site in the UK that still has them, but only in black (plus one XL in blue). Not for me, not in black, but just for reference, are they true to size? From Gore's US size chart it looks like I should take a medium, where I take a small in most tops.