The Metolius River is absolutely trending great, especially if you love the dry fly fishing that September brings. 
The next 6 to 8 weeks on the Metolius are some of my favorite dry fly days of the season. I have purposely left days off the lake boat over the next 4 weeks so I can be on the Met! Will I see you there?
This weekend below Bridge 99 for sure you need to start carrying your 8-10-12 Green Drakes. This means nymphs, emergers and duns. Also #14’s to cover the transition from Ameletus to Flav’s as both are similar mayflies and one is on the way out as the other is just about ready to roll for Fall. 
PMD’s #16 and BWO’s #18-20 will be very important in September. Of course you need to fish the cycle of these hatches from nymph to emergers and cripples and duns and finally spinners at dusk or in the early AM. 
The caddis hatches have been amazing in late august and if history repeats itself they will be amazing-er (haha) in September. Micro Caddis #18-20 Yellowish Tan, Olive #16, Tan #16, Grey #14 and October Caddis #8 are all on the menu now. Pupa and Adult and spent egg layers will be important dry flies to fish this weekend and throughout the week. It is also going to be above average temps (both daytime and overnight lows) for the next 7+ days, and that my friends is caddis weather. 
Golden Stones are still super important at the end of August and well into September. Anywhere from the headwaters to Gorge, but keep an eye on them in the Canyon, and down through the Bridge 99 area. Also keep looking for Salmonfly’s as they are an isolated hatch this time of year, meaning they are definitely not spread out all over the different river sections and because of thermal barriers in the river they don’t march upstream like on other river systems we fish. Meaning, enjoy it when you see it, but stick 3 salmonfly dries on your pack for the day this week. Why 3? One for the tree, one for the fish and one more for the fly box. 
A an explosion of Little Olive Stones is just beginning. The Henryville or Hemingway in a #16-18 with the hackle trimmed flat off the bottom will serve you well. Did you try my Yellow Missing Link suggestion? Now the Flav’s are out add an Olive Missing Link too. Missing Links are an underrated fly and match more than one thing well. 
Plenty of good nymph action now, we prefer the euro/tight line techniques and have great success throughout the river with perdigons and caddis pupa and tungsten micro mayflies. Also carry stonefly nymphs, green drake nymphs (a Tungsten Jig 20″ is a winner!!!) and Zebra Midges. 
May we suggest giving the Bull Trout a break over the next 2 weeks? It is BT Spawning time and we ought to respect that….