Areas just south of the Stateline may have seen some rare clouds Sunday afternoon. In meteorology, they are referred to as hole-punch clouds. They develop within an altocumulus cloud layer, which are usually high-level clouds. Conditions have to be perfect for their formation. In this satellite image from earlier this afternoon, you can see a few little "holes" in the clouds with little white feather-shaped clouds inside the "holes." So what causes these rare clouds to form? The altocumulus cloud layer is composed of small water droplets that are below freezing. If ice crystals can manage to develop in the layer with those droplets, they will grow quickly and potentially shrink or evaporate the water droplets. As a result, the "holes" appear in the clouds as if someone punched a hole straight through the cloud layer.
Believe it or not, humans can lead to the formation of these "hole-punch clouds." When aircraft fly through an altocumlus cloud layer, studies have shown that it can lead to the formation of larger, heavier ice crystals. And because they're so heavy, gravity causes them to fall to earth, thus creating the "hole" in the clouds. Typically within the cloudless area exists some wispy cirrus clouds, which are the ice crystals.