This series is shots of a cold front passing just before sunset. Video would have been more interesting, but if you look at the change in each picture, you get the idea.
In a frontal passage like this, the wedge of cold air, close to the ground, forces the warmer,moist air up. This creates the visible cloud.
The start.
The upper cloud is the warm air and the lower one is the cold front
The color change in the cloud now is because of the sun angle.
Looking at the back side, after the passage
and finally we end up with a sunset...
This whole sequence, covered about 15 minutes. It was great fun watching it progress.
