Three Creek Lake has been a highlight this week, with my friends Rod and Rob (unknown to each other but only a consonant apart) reported wonderful fishing out there, and another Rob with Purple Chubbies.
Here is Rod B said: Just came down from the lake and had an interesting day.   WE hung out at the big beach because we were with kids and dogs, not intending any serious fishing.  About 1000, the water along the drop off there began to boil with splashy rises. I assumed calibaetis spinners but could see nothing on the water.  Started with a spinner, and fished through the nymph – soft hackle – emerger – spinner progression.  Finally started to catch fish on anything with an upright wing in sizes #18-20.  Color didn’t matter but the wing did.  We left about 4, fish were still rising like crazy, I’d fished off and on for a total of maybe 3 hours, and hooked in excess of 50 fish, up to 18-19″, all but one were brookies.
Water temp there was 60-62 on the surface from the two little creeks that come in there, warmer on the flats.  
Rob was doing his best on Ants. You should try a sunken ant too. We have a cool little bead head version good for a dropper or on its own.
As always, Beetles and Hippie Stompers. Lots of callibatis and black caddis hatching.
Balanced Leeches, Chironomids, CB Cate, Red PT, Sheep Creek, Wooly Buggers and Poxyback CB nymphs.