Julius Glasson dropped a 35m goal to give Southern a last-minute win over Pirates to retain the Jack Hore Memorial Trophy at Bathgate Park.
Southern played with the strong wind at its back and looked to have the game in its grasp when its forwards had the edge and led 10-3 midway through the first spell.
The only try of the game came when big midfield back Luke Herden broke through the Pirates defence inside the 22m and flanker Carl Anderson was in support to score the try.
But a change came over the game after this with the Pirates forwards getting a slight edge and lock Nic Wilson dominating the line-out.
The Pirates loose trio of Warren Kearney, Josh Clark and Garth Swan made life difficult for the Southern backs by hitting them behind the advantage line.
First five-eighth Glenn Dickson used the wind to his advantage and kicked Pirates back into the red zone.
He kicked penalty goals after two, 23 and 37 minutes to take Pirates into the lead.
The winning points came after Southern won a scrum on halfway and edged forward with the pick and go to put Glasson in position for the dropped goal.
Southern 13 (Carl Anderson try; Joe Burford conversion, penalty goal, Julius Glasson dropped goal), Pirates 12 (Glenn Dickson 4 penalty goals).
Half-time: Southern 10-3.
Referee: Ross Barnett.
