I found a number of references on Rhyssa alaskensis. The original 1902 description by Ashmead agrees well with this image. In particular: the legs here are red...except for the coxae, hind tibiae, and tarsi, which are all blackish. Like all Rhyssa, it seems their larvae feed on various siricids which in turn feed mainly on conifers.

Merrill (1915), considered R. alaskensis to be synonymous with R. persuasoria, which appears to have all legs red to yellowish (including the hind tibiae and tarsi) in this image, but to a lesser extent in the additional images here. But Rohwer (1920) considered the two species to be different, and they were listed as distinct the 1979 "Red Book" (Vol 1, pg 352) by Krombein et al(1).

The only species Krombein(1) listed for CA are R. alaskensis, persuasoria, and ponderosae. I couldn't find Townes 1960 work, where R. ponderosae was described. I'm assuming there may be a key there that might allow a more certain ID here (though I've sometimes found Townes treatments hard to work through! :-) But regarding R. ponderosae, I'm guessing it's associated with ponderosa pines...and there were no ponderosa pines in the vicinity here (though there is a very unusual disjunct population of Pinus ponderosa about 17 miles to the southeast in the Bonny Doon area growing at fairly low elevation only a few miles from the Pacific...which is very strange for ponderosa pines!).

My assessment was based upon the Townes key. I thought this would be available in Google Books, but Google says "No ebook available" for this work. It is not Krombein but rather me in Krombein et. al. That's how old I am. :( R. ponderosae has a white stripe on the "temple" (gena). The ponderosae holotype was collected on ponderosa pine by forest entomologist, G. R. Struble.

...including correcting my inadvertent mis-attribution! I had simply searched the PDF of the "Red Book" using keyword "Rhyssa" to find the genus entry. Only after your comment here did I rummage further through the text and notice that the table of contents indicates the 425 pages treating Ichneumonidae were written by Robert W. Calrson. You have my sincere admiration and appreciation for your dedicated work in promoting more knowledge of this huge, difficult, and fascinating group of organisms!! (And also my apologies for carelessness in citation...now I guess I'll fix some crow for dinner :-)

So, to summarize ID points for this post, the absence of a white stripe on the temple here eliminates R. ponderosae, but "possibly R. alaskensis" is the closest we can currently get to species (i.e. presumably there are no clear characters visible in the photo that would eliminate R. persuasoria...and/or other potential alternatives).

For separating persusoria from the species of the amoena species-group, which includes alaskensis and ponderosae, Townes relied primarily on the form of the sternal sclerites of the metasoma, which would almost never be seen in any photos.

...and there is a character there (at the end of many in couplet 3 in his key to Rhyssa) that eliminates R. persusoria here!

Namely, R. persusoria has "temporal orbit partly or entirely white". The temporal orbit (i.e. area posterior to the eyes) in the individual in my photo is entirely black...as is the case for R. alaskensis (see also the color patterns shown for the various species of Rhyssa in the figures from pg. 613 of Townes(1960)).

In particular, "Figure 317 d)" there fits very well with my photo...and with the details on the pattern of white markings (and leg colors) given in Ashmead's original 1902 description of R. alaskensis.

All this indicates Bob was correct in his ID suggestion of R. alaskensis. (Wish he were still with us. He is missed.)