I fished the South Fork late yesterday afternoon into early evening. Caught three decent cutts between 8" and 9" and many 3-4". I used a size 16 tan elk hair caddis. The water is in great shape.
I fished the Middle Fork (lower section) a few days ago for an hour or so. The water is still a bit off-color, but I still managed to hook a few small cutts on an elk hair caddis. I probably should have gone sub-surface but was too lazy to change my fly.
Both forks are very fishable right now. The south fork of course has better access, but you'll be able to find fish eather way. For the middle fork head up the middle fork road until you find water you like. The fish will be there. For the South, exit 42 area is my preference.
I've been hitting it big lately with elk hair caddis and caddis emergers. There has been so much surface action lately I haven't spent to much time nymphing, as I usually do. If you go underneath, a pheasant tail or prince work great through the riffles.
Last monday my wife and I caught and released about 15 fish. most brought in by her, and she being new to the sport it was a lot of fun for her. Nothing big, 8-12 inches, mostly 8.
Almost anything will work at Snoqualmie. I nail the fish on attractor flies from stimulators to coachman and royal wulf. You can also nymph the stream but I find it more fun to catch them on a dry. There isn't too much food there so most the trout are willing to hit anything there. It's a great little river that's only 15 minutes away from me.
I actually just walked in the door from fishing the South Fork. The levels are just beginning to fall into the "hot zone". August is the time to fish in these rivers!!! I had good action casting a light variant, as well as a mix of different Adams colors. Tie something that has a dark peacock body, elk tail and grizzly hackle. Those fish could not stop hitting that thing for me!