I was up at Stagecoach on Sunday 4/23 and the res was completely ice free. Asked the ranger at the entrance gate when the ice came off and he said on Thursday 4/20. Since then the weather has been unseasonalbly warm so I would think that Willies Fork is ice free. It would be a good time to hit it up.
On Sunday I was trowing pike flies in the shallow bays and caught 3 small pike, missed 4 or 5 more, and had one decent strike. I only fished one bay for an hour or two. They are in shallow, but hooking up just depends on the fish's mood and where they are in the spawning cycle. I think the pike are just getting into their spawn up there so it can be day to day.
I know in Lake X the ice came off a couple of weeks ago (2 to 3 weeks). Pike fishing was good the first week or so and then the fish started spawning heavily and action slowed. About 10 days ago a friend of mine was there fishing for pike and saw lots of big fish paired up in the shallows which indicates to me they are in the peak of their spawn. It generally takes a few days for pike to complete their spawn, then another couple days to a week of recovery after the spawn, where they rest and are not real active. Then after their recovery it is time to eat and they will be more predictable. What I am trying to get at is the cycles of different lakes at different elevations. Lake X should be great right now so I would expect Stagecoach will be good in another two weeks or so. Willies Fork is just a bit later than Stagecoach IMO.
It can be day to day, weather dependent, time of day, and so many other factors. The best thing to do is to get as much time on the water during peak times. Peak time would be between now and mid June.