The 32-year old Gambian-born former Norway international signed with the Timbers in early May after spending some time with Saudi Arabian outfit Al-Wehda but only joined the MLS outfit late last week.
Former Valerenga, Roda JC and AIK centre-back Kah, who was an unused sub in the 2-2 draw with Vancouver Whitecaps on the weekend, is expected to bring plenty of experience and assuredness to the Timbers backline according to head coach Caleb Porter.
"We've only seen him a day and a half, but we've already seen him prior to this, watched him a lot in person and on film," Porter said. "We know his quality.
"We expect Kah to step in and make an immediate impact in our club.
"We have to be smart with how we acclimate him. He's not been with the group. He's going to take a bit of time to get his fitness up to speed. He's been working on his own, but he hasn't played in a competitive game in almost a month. So we have to be smart with how we integrate him in the group, but he's going to be a nice addition to the backline."