...for the reasons detailed in my comment of 2/15/15 below. I don't know whether Terry or John read and thought over that comment or not. I didn't move it earlier out of deference to their views.

But if they did read my comment and disagreed, they've had plenty of time to think about the things and provide a compelling rebuttal ;-)

BTW...a new revision of Adela is underway. Perhaps it will shed more light on the distinctions between these two species? I'm eagerly awaiting it's appearance...hoping it will provide lots of new info and help us all in identifying Adela posts.

Terry, regarding orange vestiture on the head...a significant qualifier was omitted in your statement above, which I've inserted in red below:

"In Powell's key, males of A. eldorada are diagnosed as having the vestiture of the crown mostly or entirely orange, [...], whereas males of Adela trigrapha have the vestiture of the crown mostly or entirely black, and [...]."
Thus if this were a male, then the abundance of orange scales on the crown would indeed be indicative of A. eldorada, even though that species has previously been associated mainly with lower-to-mid montane locales in the Sierra Nevada of California.

But the individual in the photo above is a female, as evidenced by the relatively small eyes. Per the key on pg. 215 of Powell(1): males of both A. trigrapha and A. eldorada have eyes extending on to the crown, with eye diameter 3× or more the distance between the eyes...which is not the case here. Compare the eyes here with those below:

            A. trigrapha               A. eldorada
     

Note also that...although males of A. trigrapha have heads predominantly black...females of A. trigrapha have bright orange vestiture on their heads (like females and males of A. eldorada), as stated in Powell & Opler(2) and seen in this photo. Thus the conspicuous orange head in the post here does not necessarily make eldorada the compelling choice.

Secondly, regarding the relative width of the wing bands...note that the discrepancy is not so great between the female trigrapha in the coastal CA post below and the two putative female eldorada from Washington:

            CA trigrapha             WA "eldorada 1"             WA "eldorada 2"
           

Moreover, in his discussion of trigrapha Powell(1) states on pg. 221 (purple emphasis mine):

"Northward in the coast ranges the moths average slightly larger than in the San Francisco Bay area, with somewhat larger, somewhat yellowish forewing bands and generally more orange in the crown, mostly one-third to one-half the scales comprising the occipital tufts, thus approaching eldorada in these regards."
Extrapolating from the above, the width of the wing bands in populations of trigrapha as far north as Washington might become hard to distinguish from those of eldorada.

Some other things to consider:

1) the description of eldorada in Powell(1) stated that the 3rd white wing band was often broken (in 70% of males and 45% of females sampled)
2) Powell(1) found eldorada tended to occur in semi-shaded spots in the forest or more-or-less open chaparral in canyon situations. In contrast, trigrapha occurred in more-or-less open meadow or grassy hillside situations where the larval host plant Linanthus grows.
I asked Jerry Powell about the putative WA eldorada posts here, and he commented that he'd be more comfortable with a new state record for Washington if it were based on male as well as female specimens ...which is a very good point, as couplet 7 of the key in Powell(1) indicates that a preponderance vs. paucity of orange scales on the crown separates males of eldorada vs. trigrapha, respectively.

Apropos to that point, note the lack of any perceptible orange on the crown of the male below:

       

Note also that the male in that post is from the same locale (Dog Mountain) as the putative female "eldorada 2" below:

       

So while, a priori, an extension of the known range of A. eldorada from the Sierra Nevada of California to Washington State is certainly possible, until a male with a preponderance of orange on the crown is found, it seems equally possible (and, from the above, arguably more likely) that this is A. trigrapha.

Thanks for the updates. I wasn't positive on which of the two species was correct because of the variation.