The Seattle Sounders jumped above the
With 66,452 watching on, Seattle roared ahead in the 25th minute with an own goal from Mamadou Danso, who in attempting to clear a cross from Christian Tiffert succeeded only in planting a volley past goalkeeper Donovan Ricketts.
Seattle pulled further clear of their derby rivals when Eddie Johnson swept a left-footed shot beyond Ricketts three minutes later, having been left unmarked by the penalty spot.
And the scoring was complete after 62 minutes when Fredy Montero tucked the ball in after a scramble around the edge of the Portland six-yard box.
Seattle, who still have a game in hand over all their Western Conference rivals, are three points behind second-placed Real Salt Lake and two clear of reigning MLS Cup champions
They snatched a 1-1 draw against the Conference leaders though, with a 90th-minute effort from Eddie Gaven cancelling out a 10th-minute opener from CJ Sapong.
Chivas USA and FC Dallas also battled out a 1-1 draw, with
Chivas sit bottom of the Western Conference, while