It’s wonderful when clouds have lovely flat-bottoms. What you’re seeing is the exact spot where the temperature has cooled enough to cause water vapor to condense and become a cloud. Sometimes is very pronounced - which is so cool to see and fun to paint.
Pilot Rock, Viewed From Mount Ashland, Oil on Panel, 7.5” x 10”
I made this painting on Mount Ashland, from the back side of the bunny-hill, looking east toward Pilot Rock.