March 30, 2015: At dusk, while stopped at a traffic light just north of the Texas Capitol near downtown Austin, I peered through the windshield trying to figure out this cloud formation. Was it a jet contrail? Some kind of trippy clouds I’d never seen? For help, I recently turned to meteorologist Aaron Treadway of the Austin/San Antonio-based National Weather Service.

The formation does look like an aviation contrail, Treadway replied in an email. The clouds around the contrail, he explained, are a mix of altocumulus (puffy, mid-altitude clouds that resemble cotton candy) and altostratus (gray or bluish layers of striated or fibrous clouds in the mid layers). “It looks to me like the jet flew at the same altitude as this cloud layer,” Treadway wrote, “leaving behind the contrail and splitting the cloud deck, then over time the contrail spread out producing the smooth line down the middle.”