The pilot reported that he was flying cross-country to his home airport. While en route, the pilot determined that weather conditions prevented continued flight to his planned destination, and chose to divert to another airport. According to the pilot, while en route to his diversion airport over mountainous terrain, he encountered low ceilings of about 500 to 1,000 ft above ground level and strong downdrafts. The pilot was unable to maintain altitude and impacted rising terrain, resulting in substantial damage to the fuselage, empennage and both wings. The pilot reported no preaccident mechanical malfunctions or failures with the airplane that would have precluded normal operation. He stated that the accident would likely have been prevented if he had stopped at an airport he had passed prior to reaching the mountainous terrain.