The pilot reported that before landing in gusting crosswind conditions, he verified the crosswind component was within the capability of the airplane and completed the descent checklist. After crossing midfield, he entered the left downwind leg of the airport traffic pattern and observed the windsock favoring runway 5, with wind “10-11 o’clock off the runway”. The before landing checklist was completed, and he planned to add 15 mph to his approach airspeed and utilize 20°of flaps. During final approach, reported wind was 340° at 15 knots, gusting to 27 knots. In the landing flare, the airplane encountered a “down forward forcing wind from the rear of the plane”, followed by a gust of wind from the left, before a go-around could be initiated. The airplane subsequently exited the runway, went over an embankment, and nosed over, sustaining substantial damage to the fuselage, wings and empennage. The pilot reported that there were no preaccident mechanical malfunctions or failures with the airplane that would have precluded normal operation.