I grew up there. Had an era in the late 90s/early 2000s where we did awesome for big trout in the sand dunes area. But all the warmwater species just never seemed to fish as well as it seemed like they should. Potholes was always better. But I haven't fished Moses Lake in probably 15yrs. I'm sure there have been changes.
I went, I fished and.... I couldn't get them to take a fly. First day was very windy and hot. It was hard to position and hold my pontoon boat in place. Second day in the morning more of the same. Calmed down a bit in the evening but still no luck. Last day and a half wind calmed down and we had a light rain. I caught several the last day. Hate to admit it but I wasn't using fly gear the last day.