According to the pilot, the approach to the runway was very stable. He performed a wheel landing in the tailwheel equipped airplane and touched down on runway 20 just past the numbers on the centerline. Before the tailwheel settled onto the runway, a gust of wind struck the airplane. The pilot corrected the airplane, but another “stronger” gust struck the airplane again resulting in the airplane veering off the right side of the runway. The airplane impacted the snow in the grass area between the runway and taxiway and came to rest inverted, resulting in substantial damage to the vertical stabilizer. The pilot reported no preimpact mechanical malfunctions or failures with the airplane that would have precluded normal operation. The winds reported at an airport 7 miles to the north of the accident location were from 240° at 9 knots.