Zen,Zen,Zen, shame on you for promoting fishing for whitefish with Arghhhhhhh,WORMS. Don't you know that they are a great fish to flyfish for.
Any smallish nymph pattern bounced along the bottom or fished deep under an indicator in the deepest pools will catch whitefish on most rivers all winter.
In E.Wash they often seem to prefer wet flies with a white wing. The impatient put a few maggots or a mealworm on the fly if the bites aren't coming fast enough. Keep your maggots under your lip like a chaw of tobacco or they will freeze on ya. Don't worry,they don't eat much.