Can be snow-covered, December through March.
Flat Creek is an ATV trail that has a number of fun whoop-dee-doos. The area recently burned and is open to mountain bikes, but currently closed to motorized users for 2015, so it is nice and quiet out there.
The trail starts with a descent and the climbs up the creek bed. The trail is not overly exciting, but is a scenic climb with reasonable grades.
The trail can be loose in the fall and there are some deep water crossings in the spring, but that is part of the fun.
There are lots of connecting trails around that can be used to make this ride into a loop.