Frequently we have some beautiful clouds around here ... I need to practice if I'm ever going to be able to capture their formations.
The two images on the left are, from the top left, a pencil value study, bottom left, gray, black and white value study.  Middle image is the photo I worked from ... and last is my little watercolor.   
For some reason I'm not able to upload the better photo I took.  Maybe its for the better.
If you click on the image you can enlarge it........

