Steve,
Modern cars run the A/C to dry the air out when using defrost. My Opel was a bear when it rained as the slightest moisture just turned into warm moist air blowing onto the cold damp windows and the situation actually got worse.
Living in Seattle means that winter isnt really a dry season, so you may have to plug the leaks or add an aux heater. if you are looking for function, a simple aftermarket auxilary cooler with a fan works wonders for pushing hot air.
The Mojave is also a good choice.
Just my opinions.
Scott
