It looks like voter turnout was somewhere in the mid 50s in Central Washington. That is about par for the course in an off year election. Kittitas came in at the highest at 57% (probably due to the controversial Ellensburg City Council elections). Skamania was the lowest at 49%
You can see all Washington State Counties here. Here’s the breakdown for Central Wa.:
Benton 54.1
Franklin 50
Grant 53
Kittitas 57
Okanogan 52
Skamania 49
Yakima 51