Frequently the trout feed on emerging caddis an inch or two below the surface and it is easy for us to mistake these trout for surface feeders. A good ploy is to fish a Mr. Rapidan Soft Hackle Nymph (Olive) size 16 as a dropper on 18 inches of 6X below a Mr. Rapidan Delta Wing Caddis (Olive) size 16. Often they take the dropper rather than the dry. The Murray's Flying Beetle size 16 and Mr. Rapidan Ant size 16 are also productive for this time of year.
The spotty rains have helped the streams a little in the Shenandoah National Park but they are still low. You will get your best fishing by coming in from the lower boundaries of the streams and hiking in about 45 minutes. Be sure to watch/hide your approach as the trout are wary with the low water levels. Don't get behind someone because what they didn't catch they have already spooked. For more information on these streams, check out my book Trout Fishing in the Shenandoah National Park.