I finally bailed on my first time lapse and shifted the camera west to grab another time lapse at 12 fpm looking at this scene.
I usually leave autoexposure on during my time lapses and so I did with the second time lapse I started. At the beginning the camera was shooting 1/125th of a second at about F4.5. But the shutter started to slow down to gather enough light to make a perfectly exposed image for each frame.
The result is something that isn't quite real. At first, the sun is directly illuminating the clouds and there is plenty of light. Later on, the scene goes gray for awhile as the clouds lose direct sunlight. But then color begins to reappear and intensifies right up to the end. The scene at the end is really a lot darker than the beginning but the cloud bases must be receiving secondary illumination from clouds further west that became directly illuminated by the setting sun as you see below.