North of Donner Summit, near Truckee, California in the Sierra Nevada. A nice cirque lake that is privately owned by a small and evidently very pricey resort (note the green roof across the lake). But you can hike to this point and view the lake for free! The inset shows a different view. The mountains on the skyline are the Carson Range.
PS: And there's a different Frog Lake, by Carson Pass, also in my collection. Another one of those generic names--