The evening caddisfly hatches are excellent and many trout are feeding well upon them. I'm getting my best fishing with the Mr. Rapidan Delta Wing Caddis in size 16 in both olive and black. Fish these on a 6X Classic Hand Tied Knotted Leader.
With the spotty rains the streams are still holding extra water so you will get your best fishing by coming in off the Skyline Drive or headwaters of the streams. The water temperature earlier this week was 62 degrees. The fish are wary so watch your approach.
My book Trout Fishing in the Shenandoah National Park includes information on hatches, techniques and access to the Park streams. There are 3 maps that cover the Shenandoah National Park (northern-Map 9, central-Map 10 and southern-Map 11). I reference the Milepost access to the streams in by book to coincide with the maps.