Fallstreak hole over Chilton County this morning. Here’s what’s happening... That cloud layer is made of *supercooled* water droplets — liquid water colder than freezing that hasn’t turned to ice yet. When something disturbs the layer (often a jet climbing or descending through it), a few droplets finally freeze. Those ice crystals grow rapidly, get heavy, and fall out of the cloud as faint streaks — the “fallstreaks.” As the crystals fall, they leave that clean hole behind. It’s completely harmless, produces no weather at the ground, and usually fills back in within an hour or so. These form in exactly the kind of rippled high cloud decks (cirrocumulus and altocumulus) we’ve seen today. Photo from Dana Smith