Added to MPG, thanks!

Moved from ID Request.

Several other species are very similar, but after going over the info here and the plates on MPG, BOLD and PNW MOTHS, this is the only thing that I cannot rule out. Some of the closest look-alikes are not known to reach California.
PNW MOTHs states that "Isolated populations are found on Mt. Shasta in northern California". I'm pretty sure that is very close to where you found it.
This species is quite variable. So, I expect that many examples will go unidentified for a long time, until DNA or expert analysis can sort them out. This one has a particularly bold pattern, with a little bit of orange colored highlights.
I will ask a few experts to double-check it. Some similar species are listed on the info page, but I would add to that Lasionycta sierra, Lasionycta macleani and Lasionycta discolor. (not known from your location)

Here is a note from Lars Crabo:
Bob,

Lasionycta without a doubt. I think it's uniformis, subspecies shasta. There are not a lot of them in collections, and all specimens of the California subspecies are from Panther Meadows on Mt Shasta. This moth also looks a bit like a very colorful specimen of Lasionycta luteola (as found in SW British Columbia), but L luteola is not known from much south of the border with Canada. The little we can see of the hindwing is also more like that of L uniformis. As far as the other choices like L sierrae they have a brown rather than gray groundcolor. Jim Troubridge and I collected in the high Sierra near Tioga Pass many years ago. We got sierrae there, but no uniformis. [(...that far south, near Yosemite)]

Hope that helps.

Lars