The pilot reported that during the landing flare he encountered a gust of wind and then during the landing roll the airplane departed the runway to the left. During the runway excursion, the right main landing gear separated from the airplane, and the airplane skidded on dirt and rocks parallel to the runway. The airplane sustained substantial damage to the firewall. A review of recorded data from the automated weather observation station located on the airport revealed that 5 minutes before the accident wind conditions were 310 degrees true at 3 knots. The airplane was landing on runway 33. A review of recorded data from the automated weather observation station located on the airport revealed that 15 minutes after the accident wind conditions were 340 degrees true at 19 knots, gusting to 26 knots. The pilot reported there were no preimpact mechanical failures or malfunctions with the airframe or engine that would have precluded normal operation.