Missing gridded NUCAPS data in complex terrain?

I noticed there were a lot of mixing pixels in the NUCAPS gridded data over the Black Hills despite the fact there was no notable cloud cover. Expanding west, it became apparent this was a common theme across Western Montana into central Idaho as well. Sounding availability overlays show most of these area are considered yellow. It seemed many of these points were areas where there was a gradient between darker forested areas in the terrain, and lower adjacent valley locations. For locations in the west, for this data to be useful and for us to have confidence in using it, we really need a more complete data set. A sounding from the Black Hill is shown at the bottom, which seems meteorologically reasonable.

-64BoggsLites