The pilot of a glider reported that he encountered turbulence and heavy sink on the downwind leg of the traffic pattern. He added that on final approach, the glider encountered additional "heavy sink" and a "gusting headwind". He further added that the glider was approaching soccer fields short of the runway and he was able to clear an initial goal post, but the glider impacted another goal post and impacted the ground. The glider sustained substantial damage to the fuselage and right wing. The pilot reported that there were no preaccident mechanical failures or malfunctions with the glider that would have precluded normal operation. A review of recorded data from the automated weather observation station located about 12 miles to the east of the airport reported that about 14 minutes after the accident the wind was variable at 6 knots, gusting to 15 knots. The airplane was landing on runway 25.