This is a super fun, fast and flowy rolling descent to Upper Priest Lake and to the nearby Trapper Creek Campground. It's all singletrack and mostly downhill on the way in, but is nearly as fun climbing back out. Although its a bit of a short ride by itself, this trail is a fine addition to either a post-Shorline Trail or Upper Priest #308 ride.
At the parking lot, cross the road and enter the forest of large cedars, hemlocks, and ferns. The trail will flow nicely the entire way down to Upper Priest Lake with some rolling terrain mixed in. But don't let this scare you, as its not at all a difficult climb out. There are only two steep sections on the return, and they are only about 50 feet in length. Otherwise, the trail rides great in both directions.
The trail is predominantly Douglas fir for the first few miles then drops down into an area of old-growth cedar.
Once you see the lake, bear left and follow the sandy singletrack out onto beach and enjoy the view of Upper Priest Lake. You can continue a little ways down Idaho Department of Lands Trail #58 to reach Trapper Creek and the adjacent campground. Once you're ready, turn around and enjoy the deceptively pleasant climb out back to the car.