To my knowledge the bird has not been detected since about 9:10 this morning.
I arrived at the Washington Park Arboretum in Seattle at 7:30, and by 7:40 was at the Pacific Connections garden, hearing a familiar song from my years in the East coming from the golf course border area. I spent the next half hour listening to the Northern Parula and trying to see it. Eventually I got one view of it about 100' up in the cottonwood where it seemed to spend the entire time, seeing it deliver a couple songs. There were many young and scruffy Golden-crowned Kinglets (wing bars!), two chickadee species, creepers, juncos, Song Sparrows, and nuthatch up there to distract, so be careful. There were also several (at least four) loud machines blaring most of the time from the golf course maintenance nearby, then when they let up some, arboretum maintenance began. Mowing, blowing, pushing a tree over, sawing. It sounded like being on the flightline of an operating airport.
Many birders arrived after 9:30, and we await news.