WA 20 which takes you through North Cascades National Park is closed for the winter. No way around that one.
The road to Paradise on Mt. Rainier is kept open during the winter, weather permitting. Bring skis or snowshoes if you want to do any treking.
Hurricane Ridge Road is usually open during the winter, weather permitting of course. Again skis or snowshoes if you want to get out of your car. You can also drive out to the Pacific Coast but it's a long way.
Weather is highly variable and dangerous if you are not properly equipped. Make sure you have chains, gas and extra clothes/food.