Originally Posted by liv2fish
Can't tell you exactly how it will be but you can def. catch fish throughout the year in CO. I didn't fish this past winter b/c I was skiing too often but the year before I fished quite a bit throughout the winter. If you know what a "tailwater" is, they will all produce fish. Its a section of river coming out of a damn below a res. The Blue and Taylor would be my recommendations. Sections of the S. Platte as well. Some very BIG fish can be caught in these tailwaters on very nasty days. Catching fish on tiny dries while its snowing is even a possibility. If you have any specific questions feel free to let me know and I'll try to help.
All Liv2fish's advice is good.
If I were to add anything, it would be that winter fishing in Colorado can be very difficult due to the lethargic nature of fish in the colder water. Your presentation must be totally right on and your choice of fly is also very important. The take or strike is also very subtle so sight fishing is usually your best bet. Watch for opening mouths or slight movement of the fish in the direction of your fly. Strike indicators are a must also.
Fish in winter tailwaters will not move far to get food.
Hope this helps.