Can you talk a little about your gear selection for this time of year? What gear is different from your May CDS.
I'll be there in May 2016, but, I'm also kicking around a winter walk.
Like everyone else we focused on layers. We also thought we might have to spend a day or two walking in freezing rain but the coldest we walked in was 40 F with a light mist/rain and so we were over prepared. But we're still on the Camino and a cold rain is predicted for Monday and Tuesday - so our thoughts might change. In any any event, since the weather is changeable I'd probably bring the same things next time.
Our list was the same as our summer list which was derived from everyone's list here and so it was pretty sparing. Our summer gear included light sleeping bag (1.5 lb), 1 pair pants (worn), 1 pair shorts, 1 extra shirt, change of underclothes, tevas, 2 extra pair of socks and liners, sweater, rain coat and rain pants, warm hat, ball cap for sun, toiletries, computer gear, and not much else.
For winter we replaced the light rain coat (0.5 lb) with a heavier (1.4 lb) and warmer wind proof, water proof shell. For the upper body we added a light long sleeve T-shirt, fleece vest, and down sweater. The upper body body layers were long sleeve T-shirt; button up long sleeve shirt; tight woven, heavy cotton sweater; fleece vest; down sweater; and shell. We never wore all of this together. The inner T-shirt will left at home next time. The working outfit was shirt, sweater, and shell or vest. And there were a few time I was happy to have the down sweater and it was 0.75 lb so I would bring it again.
For the bottom we added base layer pants (never worn) and gaiters (never used). The gaiters and base layer pants are nearly 1 lb (0.9 lb) and so I have mixed feelings about them. If I were going for 3 weeks again, I might look at the weather forecast and leave them at home but they made me feel prepared.
We also added a neck warmer (or neck gaiter) which we have not used, gloves (used extensively), tightly woven fleece mittens, and waterproof mitten shells. On the cold rainy day the mittens and mitten shells were a enormous blessing.
Beyond that because we were expecting rain, we put everything (yes - everything!) into light weight dry sacks of various sizes and colors. It helped with organization but added about 0.75 lb, I would probably do it again (maybe).
Overall our packs were about 3 (my wife's) & 5 lbs (mine) heavier than summer, helped by a new and much lighter computer and a small reduction in incidentals that we hadn't used in the summer.
This is what we did - but your mileage might vary (and we'll see how we feel a few weeks after the conclusion of our short Camino).