Moved from Adela.

Looks like Adela septentrionella, and indeed that's what it keys to in Powell(1969). This is a male, as can be discerned from the very long antennae (> 3 times body length), and the long tuft of bushy black scales on the head (females of this species typically have orange scales on the head).

It's on rosaceus flowers in the photos, which at first I supposed would likely be the host plant, Ocean-spray (Holodiscus discolor...Oregon images here). But that species has flowers with pale anthers and paniculate inflorescence...whereas the anthers are dark in your photos, and the inflorescence is a dome-like umbel, so I think it's ninebark (Physocarpus capitatus, Oregon images here). According to the Oregon Flora Atlas, both species grow in much of western Oregon.

Although this is an adult nectaring, I wonder if the larvae are just as content with Physocarpus as they are with Holodiscus?

Moved from Butterflies and Moths.