Beautiful clouds may be seen on many days just above the Flatirons, the rock formations just west of the NCAR mesa. These clouds are caused by westerly winds blowing over the Front Range of the Rockies.

Air tends to cool as it is forced upward. Since cooler air is able to hold less water vapor, some of the vapor may condense into cloud droplets as it passes over a mountain range. As the air moves past the mountains and descends, it may warm enough so that the condensation stops, leaving a narrow cloud behind.

Lens-shaped (lenticular) clouds tend to form above or just to the east of individual peaks. Sometimes these appear to be circular, stacked like dinner plates. At other times, the entire north-south line of the Front Range produces a long, low cloud, called a foehn wall, along and just behind (west of) the peaks. You might also see Kelvin-Helmholtz clouds, a row of small, curving clouds that resemble cresting waves. The waves are produced by wind that increases strongly just above the cloud. All of these clouds may glow with brilliant colors at sunrise and sunset.