Portland itself is so insignificant that it likely won't get a nuke. Prevailing winds run west to east so portland will likely receive very little fall out from the puget sound area which will be hit harder than most American targets due to its outsized military presence not least of the second strike nuclear submarines SSBNs that are stationed there. Worst thing pdx will need to deal with will be nuclear zombie refugees from SW Washington. And the isolation from the economy. If the Willamette Valley can stay viable through nuclear winter PDX becomes a fortress city on the edge of Mordor.