Clouds drifting by

This isn't quite part of the advent calendar, but it is Christmas, it is The Sentinel, and it has a caption.

So... ( Click to open the non-advent calendar door. )

Okay, it's just the 13th here, but one picture took me longer than it should have. Yep, there's more than one picture there - this is a multi picture door. The reason should (I hope) be obvious.

( Click to open door number twelve. )