I' ll have to agree with a lot of what people are saying here. You might want to use beaded nymphs. Alot of flies right now are at the bottom of the rivers and streams.I also use a weight forward line. I have the great pleasure of fishing on the Missouri right now. Though it is colder than crud, I just put on my neoprene waders and hit the water. Some of the best flyfishing in Montana can be found in the winter as the crowed waters aren' t so crowded