There are three species of the mayflies that are hatching in the mountain trout streams now and the trout are feeding on all of them. I match these three hatches with the Mr. Rapidan Dry in size 14 & 16. To cover both the topwater and underwater, I put a Bead Head Prince Nymph or Copper John in size 14 on a 5X mono about 18 inches below the dry. Fish all of these on a Murray's Classic 7.5ft 5X or Mountain 6ft 5X Leader.
All of the streams in the Shenandoah National Park are fishable. You will find better water levels by coming in from the Skyline Drive or upper reaches of the streams. If you need help on access, see my book Trout Fishing in the Shenandoah National Park or download my video on the Park streams, or stop by the fly shop.