An out-of-state political committee, including committees registered with the Federal Elections Commission, not registered with PDC (that is, a PAC located in a state other than Washington organized for the purpose of supporting or opposing candidates or ballot propositions) that contributes to or spends more than $50 on behalf of any Washington state, local or judicial candidate, ballot measure or political committee must file either a C-5 report no later than the 10th day of the month following any month in which the contribution or expenditure was made or register as an in-state committee and file contribution and expenditure reports within two weeks of spending. RCW 42.17A.250. Whether the out-of-state committee files the C-5 or registers as an in-state committee depends on whether it satisfies the criteria set out in WAC 390-16-049.
Also note that out-of-state and federal PACs, like in-state political committees registered with PDC, must receive $10 or more from at least 10 Washington state registered voters during the 180 days preceding any contribution they give to a state office candidate. If they do not meet this test, by law they are ineligible to give to candidates for legislative or statewide executive office. RCW 42.17A.405(12).