Mark,
I sail all year in SC. Hard to believe, but it does get cold here. Our  
winters last from December 1st to April 1st. Some days when I leave in the  morning 
I have ice in the cockpit. By noon I'm in shirt sleeves. I would  recommend 
thermal underwear and good socks that wick moisture and shoes that  don't 
absorb moisture. Layering is important and I use a light weight long  sleeved nylon 
(?) athletic shirt as a base. It's the type used by runners and  bikers. From 
their I layer up and top it all off with a good lite weight wind  breaker 
that has a collar which can be zippered up high around the neck. I have  a good 
selection of winter hats left over from when I lived up north and they  come in 
handy. As the day goes on and the cockpit warms up I shed a layer or two  and 
switch over from a winter hat to a more traditional style baseball  cap. I've 
been in short sleeves on 50 degree days because the sun in the  cockpit is so 
warm.
A little practice will tell you what you need to wear. I always pack more  
clothes than I need and an extra pair of dry socks is really appreciated later  
in the day as the sun sets. Nothing worse than wet socks as you are putting 
the  boat to bed. If my feet are dry, I can put up with other parts being cold.
Last but not least is a sufficient supply of Mt. Gay rum. Rum always tastes  
better this time of year because you don't need as much ice to keep it  cold.
I pack a thermos of hot coffee which I drink first thing and plenty of good  
food. The nice thing about winter sailing is that the winds are usually great  
and not so many pleasure boats to get in your way. I really miss the bikini's 
 though.
 
Rummy