What an absolutely pointless thing to get pedantic about. Put "spokane washington" into Google images and tell me if that looks like a desert to you.
They're also wrong. The geographic center (around Ellensburg or so) is also in what is known as Eastern WA (east of the Cascades).
https://maps.app.goo.gl/Yud6EFprZeaVDaeQ6
This is the view outside of Fairchild AFB, which runs the training course in question.
Wikipedia reports that Spokane has a Mediterranean climate, as does Kohgiluyeh and Boyer-Ahmad province where this F-15 is reported to have been shot down.