SEATTLE - The Vancouver Whitecaps began two months of seeing their Cascadia rivals to the south with potentially their most impressive victory of the season.

Meanwhile, the Seattle Sounders losing spiral continued even with the return of Clint Dempsey.

Pa-Modou Kah surpassed his MLS career goal total by scoring twice and the Whitecaps beat the Sounders 3-0 on Saturday night, spoiling the return of Dempsey after more than a month away from the club.

Kah volleyed his first goal past goalkeeper Stefan Frei in the sixth minute off a scramble in the penalty area. He added a second in the opening moments of the second half, redirecting Cristian Techera's shot with a deft back-heel.

The Whitecaps (12-8-3) won their second straight and their fifth in eight matches, temporarily moving to the top of the Western Conference standings ahead of FC Dallas. Seattle dropped to 10-11-2.

"They put a huge amount of work in which you need to do when you play Seattle away and you get your rewards. And we got our rewards tonight," Vancouver coach Carl Robinson said. "We'll enjoy it, the result, and the performance was absolutely fantastic."

Kah entered the match with one career MLS goal in 57 games, while Pedro Morales added his fourth goal of the season in the 75th minute with a curling free kick.

It was the first of four matchups between the Whitecaps and Sounders over the next two months, including a league match on Sept. 19 in Vancouver and two meetings in the group stage of the CONCACAF Champions League. The first of those comes Wednesday night in Vancouver.

"I think the performance is a huge milestone for us. I haven't seen us play this well in a very, very long time and that's almost more important than the result for me," Vancouver goalkeeper David Ousted said.

Seattle lost its fourth straight match and for the eighth time in 10, continuing its tumble from the top of the Western Conference that coincided with Dempsey's suspension and duties with the U.S. national team in the Gold Cup. Seattle has been shutout in its past four matches, the longest scoreless streak in franchise history.

Dempsey played in an MLS game for the first time since June 13. It was his first match with the Sounders since June 16 when he was given a red card in a U.S. Open Cup loss to Portland and tore up the referee's notebook. Dempsey was given a three-game suspension by MLS and when his punishment was over, he was off with the U.S. at the Gold Cup, where he scored six goals.

But that goal prowess failed to follow Dempsey back to Seattle. The Sounders were disjointed in the offensive end and barely threated Ousted.

Seattle's best chance came late in the first half. Kah likely should have been called for a handball in the penalty are but referee Mark Geiger — criticized for his officiating in the Gold Cup semifinal between Mexico and Panama — did not make the call. The ball came off Kah and to Seattle's Chad Marshall, but his point-blank shot was smothered by Ousted.

"It's never going to be that easy," Seattle coach Sigi Schmid said. "I tried to caution people. Everybody thought, 'OK, everybody is back, so a snap of the fingers and it's all going to happen again.' That's not the way it works. You've got to get guys back playing with each other again."