Was lucky to make a trip to Yellowstone land from the 23rd to the 30th. I will give a brief report for any who may be getting ready to head that way.
We spent the first couple of days on the Madison, stayed at the Slide Inn. The Caddis hatches in the evening were mind boggling and the fish for the most part ignored them! We caught a few in the evening but nothing to brag about. The water was low, I understand they were going to let a little more water out of the lake, but was told the river was really running lean. Three dollar bridge was tough and crowded but the access is good and you can walk to find open water. Our first morning there we fished the area below 3 dollar called Pine Butte, the fish were on a Size 10 golden stone or caddis on 4x, fish were big; 15-20" with one about 12". Pulled 4 fish out of a small cut bank with a bh soft hackle (green # 16).
We then spent 2 nights in the Slough Creek Campground, fished Slough Creek first Meadow and Soda Butte and the Lamar. All were good, Soda Butte and the Lamar were clear (early from what I hear) Sulphurs on Slough Creek, Streamers or just about anything close to the bank on Soda Butte (larger fish on streamers) Elk Hair Caddis on the Lamar.
The last two days we spent in Last Chance, Idaho, fished the South Fork with a fellow named JD Miller out of Henry's Fork Anglers, it was awesome. I would recommend JD in a heartbeat! If you have not fished the SF, try to do it when you are out there. Big river (12,000+ cfs) very little wading access, though you can wade some of the riffles (full of fish) as you float the river. We fished the 3rd stretch, I hear the second is as good. Beautiful scenery, lots of fish and many big ones. We got beat up on the Henry's Fork the last day, the rise never happened so we stood around alot..... looking for them(should have tried a streamer!), caught a small brookie on the HF, whats that about?
Any particular questions shoot me an email, reference Yellowstone.