Clouds outside an old abandoned sugar mill in Longmont, CO at sunset.
These clouds are likely a combination of mostly stratocumulus and a few altocumulus clouds. Below is a skew-t diagram taken approximately 1.5 hours before this image was taken. From the skew-t diagram, we can see the clouds are forming around 5,272 meters above sea level. This would place them in the range that mostly stratocumulus clouds form (based on the flowvis guidebook), which corroborates the claim that these are stratocumulus clouds. As the skew-t diagram shows a cape of 0, these clouds are stable. This makes sense as these clouds are fairly flat.