The sulphur mayfly hatch is coming on strong. This is one of the heaviest hatches on many streams. The duns emerge from mid-day until dark depending on the stream and the spinners return the last two hours of the day. The last two hours of the day you have trout feeding on both duns and spinners. My favorite flies are Murray's Sulphur Dry and Shenk's Sulphur Dry in size 16 & 18.
With the extra water levels we are experiencing in the Shenandoah National Park after the heavy rains, you may want to try some nymphs such as the Bead Head Prince or Bead Head Hare's Ear size 14. Or if you prefer to fish a dry with a dropper, use the above Sulphur Dry with a Murray's Sulphur Nymph size 16 below it.
Earlier in the week, I found the streams in the lower boundary levels of the Shenandoah National Park to be very full of water from the recent rains. So I changed course and decided to fish the streams by coming in from the Skyline Drive. I found much better water levels in the upper reaches and off the Skyline Drive.
The water levels on the native brook trout streams in the George Washington National Forest west of Edinburg are great for this time of year.