The Metolius is a powerhouse now for Trout and Bull Trout. Not to be missed over the next several weeks. No big Drake hatches so far, but it is getting ramped up and you need to be ready.
No reason for me to rewrite this from scratch so here is the info I shared from last week that is going to be the same this week and through at least the end of the 1st week of October.
Pale Morning Duns. Likely to see both #16 and #18 as autumn days march on through September and into October. 
Blue Wing Olives. Mostly size #20, but #18 and #22 are possible. On small hooks, the % difference if you are off a hook size is greater than being off between a #12 and a #14. Meaning you might not get away with it unless you match the hatch right on. And that hasn’t taken account for what stage these picky trout are after…
Mahogany Duns. A close relative to PMD’s in #16 and just a perfect match for the Quill Gordon or Upright Rusty. 
Ameletus. #14. I like an Olive Haze, Jeff’s Flav (its a multitasker), Film Critic and Purple Comparadun 
Flav’s. A true sign of autumn. Jeff’s Flav, Film Critic, Comparadun, Parachute, Olive Haze. 
Green Drakes. I don’t expect to see them this week, but maybe they will pop on the rainy days? The september drakes are usually a #10 and #12 where the spring drakes are a #8 and #10. 
Not this early in the month (of September) but by late month some Cinygmula should be mixing in too. #16 yellow mayflies with 2 tails. Don’t worry, all the PMD flies you bought or tied will match it too.
Spinners. Rusty #16-18-20, light Olive #18-20-22, green drake #10-12-14 and look for them in the mornings and the other 2 in the evening usually. 
Caddis are in abundance with #20 Tan Micro Caddis filling the air most evenings, but they prefer warmth so tonight and tomorrow look good, but Tuesday, Wednesday and Thursday might see less of them? Lots of #16 Tan Caddis (hydropsyche sp) , Olive #16-18, Gray #14and October Caddis #8 are increasing in hatch numbers now each evening. I expect to see more of them this week with the cool weather. 
Stoneflies will be very good this week and all of September with the most abundant species coming up as #16-18 Little Olive Stones, followed by #8-12 Golden Stones, #4-6 Salmonflies in isolated hatch areas, and #6-8 Cascade Stones mostly below Bridge 99 but could be up around Wizard Falls and the Canyon. 
Midges are also a strong possibility to be a hatch of importance, so make sure to have some Griffiths Gnats #20-22 and other black emergers and pupa to fish if that shows up. 
We are using more Ants and Beetles on the Metolius than before and they work. 
Nymphs you absolutely need now are Green Drakes (TJ Hooker and 20 Incher) PMD Split Case, 2 Bit Hookers, Soft Hackle PT’s, Fat Ass Caddis, Golden Stone’s and Black Stones, October Caddis Pupa, Walts Worms and a myriad of Perdigons, especially in Brown, Olive and Purple. 
Streamers include the biggest articulated stuff you can handle, along with more manageable flies like a Circus Peanut and Milk Shake, and Sir Mix a Lot, Busta Seamz and Sparkle Minnows. Mostly this is for Bull Trout, but you can also use smaller Squirrel Leeches and Slum Lords and certainly interest some Rainbows and Browns. 
This is an intense hatch time for the next 6 weeks, and I listed a lot of flies to match the hatch. Overwhelming? Stop in the shop and tell us where on the river you’ll be, and what time you are going to fish and we can narrow it down a lot. Often to just a few hatches that will be most important in the right time and place for you.