I think one problem with using this rcw as a basis for access to the NOF meetings lies in the definition section. See highlighted section below. To me, this would not define the season negotiation meetings but the commission meetings where the seasons are finally adopted, which is a public meeting, where the final descision is made (action taken) and there is a vote that is publically taken.

RCW 42.30.020
Definitions.
As used in this chapter unless the context indicates otherwise:
(1) "Public agency" means:
(a) Any state board, commission, committee, department, educational institution, or other state agency which is created by or pursuant to statute, other than courts and the legislature;
(b) Any county, city, school district, special purpose district, or other municipal corporation or political subdivision of the state of Washington;
(c) Any subagency of a public agency which is created by or pursuant to statute, ordinance, or other legislative act, including but not limited to planning commissions, library or park boards, commissions, and agencies;
(d) Any policy group whose membership includes representatives of publicly owned utilities formed by or pursuant to the laws of this state when meeting together as or on behalf of participants who have contracted for the output of generating plants being planned or built by an operating agency.
(2) "Governing body" means the multimember board, commission, committee, council, or other policy or rule-making body of a public agency, or any committee thereof when the committee acts on behalf of the governing body, conducts hearings, or takes testimony or public comment.
(3) "Action" means the transaction of the official business of a public agency by a governing body including but not limited to receipt of public testimony, deliberations, discussions, considerations, reviews, evaluations, and final actions. "Final action" means a collective positive or negative decision, or an actual vote by a majority of the members of a governing body when sitting as a body or entity, upon a motion, proposal, resolution, order, or ordinance.
(4) "Meeting" means meetings at which action is taken.

But, I'm not a lawyer...