Atlanta is 3 hours ahead of Portland
Best overlap: 8:00 AM to 3:00 PM in Portland is 11:00 AM to 6:00 PM in Atlanta.
For a call that suits both sides, look at 8:00 AM to 3:00 PM in Portland / 11:00 AM to 6:00 PM in Atlanta. Atlanta is 3 hours ahead of Portland, but you still share a generous 7 hours of overlap, so scheduling is easy and there's room to move a meeting when you need to.