The sky was unusual in that there was a retreating  edge of cloud to the north, which I couldn’t quite figure out. The evening weather show made it clear: there was a strong spiral low in the Gulf of Alaska to the south, and the blue sky was a clear air sector between two cloud bands. The spiral was turning in such a direction that the clear band moved over us from south to north. The photo was taken looking east, and the clouds thickened to opacity just to the left of the photo.

Clouds looking east, Fairbanks 9/26/12. The feathery stuff is cirrus, blending into altostratus farther to the left.