Cold weather camping presents a whole new set of problems.
You say you will just be doing weekend trips in the winter, before I made skirting, I would look at upgrading the belly insulation and ensure it's well sealed. Open up every thing that has a hole through the skin and spray some expanding foam in to seal them up. Those plastic covers over the cable/phone inlet, water supply, etc. my so caled four season TT had more air leaks than a sieve. Look behind your electrical panel, in the cabinets under the sink. There are a bunch of holes that wheren't sealed up after the the holes were drilled and wire/plumbing run.
Condensation? More like a rain forest. Be prepared to run your range hood and bathroom vents to help move the condensation out, a humidistat wired into the range hood will help to keep the mositure moving out. I buy Calcium Chloride in 50# bags and make my own air driers using icecream buckets and plastic strainers from the dollar store. We leave the air driers in our trailer year round, until we are ready to hit the road. Last bag of Calcium Chloride that I bought cost me around $40, about a third of the cost of buying the air drier refills from an RV dealer.
Be sure to drain the fresh water before you head home, any water left in the lines can freeze up very quickly between the air temperature and the wind chill at 50-55 mph. I use a small 12V compresser to blow out the lines. Make sure the blade valves are in good shape and not leaking. If they leak, you will most likely have valves that freeze up and you won't be able to dump your tanks.
