Santa Rosa's Sonoma Bank will merge into Portland, Ore.-based Umpqua Bank as part of a $2 billion deal involving two Pacific Northwest financial companies.

Umpqua Holding Corp. announced late Wednesday it will acquire Spokane, Wash.-based Sterling Financial Corp., the parent company of Sonoma Bank.

The combined organization will have $22 billion in assets and 394 stores across Oregon, Washington, Idaho, California and Nevada.

Sonoma and Umpqua each have two branches in Santa Rosa. A Sterling spokeswoman said no decision has been made on whether to consolidate branches.

Sterling still plans on Sept. 23 to rename its Sonoma Bank and other California branches as Argent Bank. Once the acquisition is completed, likely in the first half of 2014, all the branches will operate under the Umpqua brand.

Sonoma Bank, which began as Sonoma National Bank, was acquired by Sterling in 2007 for $345 million in cash and stock.