Earlier I had guessed it might be Perdita, based on a vague sense of gestalt. But I'm often way off!

I had actually tried to see if I might be able to get to Perdita using the key in the reference for bees of the northwest by Stephen, Bohart & Torchio(1). There, the relevant key breaks to get to Perdita are initially:

1) Forewing w/ 2 marginal cells (not clear to me in the images);
2) Arolia present (yes);
8) Abdominal terga without sharply defined yellow or white markings (yes);
17) Jugal lobe > 1/2 vannal lobe (not visible in the photos, at least to me);
18) Marginal cell truncate, subtruncate, or strongly diverging from wing margin apically (cleary not!)

As this last character was inconsistent with my images, I figured I had guessed wrong with Perdita. (Of course, I did not find this bee in the northwest, and thus shouldn't expect that key to work here! :-)

Upon receiving your response, I researched a bit and noticed an earlier comment you had made on Lynn Monroe's Perdita (Pygoperdita) post to the effect that this subgenus has unusually long marginal cells for Perdita. Ah...the subtleties of taxonomy! (Perhaps subgenus Pygoperdita doesn't occur in the Northwest, and that's why the key I was using seemed to exclude Perdita.)

I also found two records on the Discover Life web site for Pygoperdita associated with Calochortus at nearby locales: Perdita bilobata collected just five miles NW; and Perdita calochorti collected 10.6 miles to the south. Intriguing. But with so many species of Perdita out there, I guess these are just leads.

At any rate, thanks again for your help. As is often the case, your input definitely focused and promoted my inquiry and learning (as I'm sure it does for many others as well :-).