Rick,
Yes, you can fish the Yak through the winter. You'll find the BWO hatch fading as the month of November progresses and temps drop.
During the winter (Dec, Jan & Feb) midges will be the main hatch and only for a short period each day. You can also nymph as well as dredging up some fish on streamers.
If the trout aren't playing, the whitefish will be all over the nymphs.