Polypro long underwear has proven to be very effective as a starting layer. Thin gloves will usually prove more than adequate. Obviously, the colder the air temps, the more you will want on. There are no services however, and the trails are not lit. Many people ski moonlit nights.
Every year is different.
Usually there is skiing for all abilities on our higher elevation plateau trails by mid-December. Again, every year is different. Skiers are pretty much assured of finding prime snow from mid-January until the beginning of March. March weather is warmer and the snow is frequently wonderful. December snow is usually good quality but sections of our vast trail system may not be fully open.