Cornus sp.

Can we see the foliage?

Sure does look like one.

Unfortunately, this is about as good as it gets as far as detail of the foliage goes. If this is indeed a species of Cornus, any idea which one? I've never seen Cornus with such thick, glossy foliage before. What's also throwing me is the number of petals: In looking on-line I now see that our native Dogwood, Cornus nuttalli, is pictured with as many as 6 petals. However, I don't know that I have ever seen one in this vicinity with more than four; ditto Cornus florida. Is C. nuttalli that highly variable?

I think you got it (nutalli).
I've never seen a dogwood bloom out of season, but apparently it does (looked up).

There are two of these trees within maybe 3 miles of each other, one growing alongside the freeway and the other in a yard (the one pictured). That was my first inclination, also: C. nuttalli, blooming out of season; however, these two are so different from the rest of the natives that once I got a closer look at them, it made me reconsider. Very dark green, glossy foliage and loaded with blooms, while the usual nuttalli are actually rather anemic-looking, even in full sun. Of course, those in the full sun do have more blooms than those in the more densely-wooded areas, but I've never seen one with this many flowers. I'll see if I can get some additional pictures of both and post them, because now I'm really curious as to exactly how these specimens do differ. Thank you!

There are two of these trees within maybe 3 miles of each other, one growing alongside the freeway and the other in a yard (the one pictured). That was my first inclination, also: C. nuttalli, blooming out of season; however, these two are so different from the rest of the natives that once I got a closer look at them, it made me reconsider. Very dark green, glossy foliage and loaded with blooms, while the usual nuttalli are actually rather anemic-looking, even in full sun. Of course, those in the full sun do have more blooms than those in the more densely-wooded areas, but I've never seen one with this many flowers. I'll see if I can get some additional pictures of both and post them, because now I'm really curious as to exactly how these specimens do differ. Thank you!

Certainly the opposite leaf arrangement helps to indicate that it could be a dogwood. Very pretty.

Dogwood often bloom twice in the PNW, once earlier in the spring and then in late summer.