Here's what I have.
The Dome is owned and run by the city. They still play the "the tenant does not allow weapons card." I haven't had time to fight city hall over the issue with my current schedule. If you have read my letters you will see that the entity in charge of the Dome is a subsection of the city and by so the no weapons signs are in violation unlike the 2 stadiums in Seattle or the one in Kent.
However you are allowed to carry a weapon per RCW 9.41.300 but prudence calls for CC. There are no pat downs or metal detectors & be prepared for bags to be searched. If found to be carrying a weapon they can only ask you to leave.