Southeast of St. Marys, the Tornado Run mountain bike trail has all kinds of terrain from waist deep streams to rolling grass flat streches. It was carved from a forest that was run over by a tornado so it gets rough at times. It is a moderately hard course and has plenty of trail options. From Clearfield, follow SR153 until you see then signs. Once you are in the park go up toward the camp ground area. Look for signs.
To reach Parkers Dam from US80, use exit 18 and follow SR153 north. Follow signs into park.
Overall, Tornado Run is the 23rd most popular mountain bike trail of all 75 mountain biking rides in Pennsylvania.