They're dropping the water now, so wading throughout the river will improve dramatically, as should the fishing if the last few days are any indication.  The dry fly fishing has been reputedly excellent throughout the day, with the evening caddis finale ending your day on a high note.  Baetis are about when the sun is hiding.  Smaller nymphs behind a big dry are a good call as the water clarity increases, flows wane, and the fish get a bit spookier.  We're coming into the best time of year to fish in this region- and the Yakima is no exception.  Suggested fly patterns include any form of hopper tight to the bank in #8-12, lightning bugs, bloody mary, copper john in various colors, all #16-20, olive X-Caddis #14-16, Blue Winged Olives #18-22, soft hackles swung in the current effectively imitate this hatch, by the way....drag free is not always the answer.  Fish the riffles and tailouts with olive softhackles during BWO hatches.