Great feedback this time! Here’s the answer…
Answer: Image is of an insulation void in a ceiling structure! Customer is experiencing severe ice dams on roof edges due to the effects of interior thermal energy penetrating the roofing structure, warming the outside material and melting the snow. The snow melt runs down to the soffit and re-freezes causing the ice dam.
As requested, here are the visible light and blended infrared/visible light images, which helps show the thermal void pattern within the visible light image:
Thanks for all your great answers! Dan and Gabe seem to have gotten the closest answers (see below in comments)–kudos!
Enjoy the rest of your Friday