I've been up here for 20 years, most of that traveling the entire region for work so I've been all over. Tri-Cities is pretty good sized, hotter and drier than many places. That should be no problem for a Vegas resident, you'd likely be chilly. Walla Walla is a great place, lots of wineries, somewhat smaller, and yet big enough for your practice. Spokane is good too but starting to lean towards becoming Seattle Junior.
@DionR is correct, the politics up here are very liberal with Seattle or Portland able to outvote the entire rest of the state. However, the state itself is a great place to live.