Both accompanied a 3-1 win over Vancouver in the final game at Empire Field before the Whitecaps move to their new home at BC Place.
After the teams swapped first-half goals, the difference was a pair of Fredy Montero goals within a short span of the second half.
The first came in the 63rd minute as Montero received the ball in the penalty area, faked right, then pulled the ball back left and fired a sizzler past goalkeeper Joe Cannon, snapping the back of the net.
Four minutes later, Montero hit a shot from the top of the penalty area. It was deflected by Vancouver defender Jay DeMerit, but the ball looped into the goal.
Those goals moved Montero past Alvaro Fernandez into the team lead with nine.
With the result, the Sounders concluded their Cascadia Cup competition with eight points from four games. Behind them are Portland, with four points from three games, and Vancouver with one point from three games.
Seattle (15-6-9) also returned to second place in MLS, moving three points ahead of Real Salt Lake, which lost to D.C. United.
The Sounders will return to CONCACAF Champions League group play on Tuesday at Comunicaciones of Guatemala.
They will resume the MLS regular season Saturday at New England.
