Road Tire Performance in Rain and Snow
Slick tires, like your conti's, have no problem in wet conditions. If the streets you ride in Boston in winter are just wet with occasional light slush you're fine with what you got. 

You'll want knobby tires if you're regularly riding in something soft like dirt, mud, packed snow or very heavy slush. Slick tires are significantly more squirrely in those conditions. In that case, typical cross tires will be better.