Don't let the high water scare ya'. If it gets up there a bit and stays about the same flow for 2-3 days the trout will still be eating. They just change their feeding lanes according to the flow.
I fished it in Feb. a few years ago at 8200cfs, water was brown and sticks floating by. Me and two other guys knocked the snot out of the fish on nymphs right next to shore and even got a decent BWO/MB hatch too.
A sudden drop or rise will throw it off for sure. I was on the river at Whiskey D1ck a few years ago. We had great fishing in the evening but a lightning hit that night at Pelton caused a malfunction in the gates and the water made a 1200cfs jump. We camped at the bottom of Whitehorse the next night, some of the best water there and fishing was horrible. Fortunately we DID have beer........