Taken September 6th on Highway 36th to Broomfield. These clouds appear to be cirrus or cirrostratus at around 6,000m. The closest sounding data that was available was from a Grand Junction station, but a related 500mB isobar plot seems to indicate that atmospheric conditions may have been relatively stable from Colorado’s Western Slope out to the Front Range. To the best of my recollection, the sky was relatively cloudless.