Yesterday afternoon, the weather shifted in our area.
And with the cold wind came these so-very-interesting cloud formations. Triss said they were billow altocumulus clouds, and that the air was going up and down through them.
I cannot name clouds that easily, so I looked it up.
From The Book of Clouds by John A. Day:
Billow clouds are organized in parallel rows. These benign-looking rows are created when wind blows at highly varying speeds in layers just above and below the clouds. These winds result in very unstable air that can be a danger to pilots. Billow clouds are often seen with altocumulus and cirrocumulus.
Look at the abrupt edge of the formation! Amazing. We had to drive into town right after I took these pictures, and we examined the clouds all the way there. They looked even more spectacular as the sun set. Gradually, the rows filled in.
Happily, this unique cloud formation took place above our house the same week as Outdoor Challenge #39: Weather Challenge #1. We have been doing a quick snatch of nature study here and there for the last several weeks, rather than participate in the challenges, but I have wanted to get back into it. I guess this is our signal to begin again. :o)
Update: Triss' narration on the clouds here.