Margaret Lamb is a local pilot in the San Luis Valley.

“Referring to the photo with the blowing dust on the left and “Star Dune” (highest dune of the monument) shadowed:

Taken from the Zapata Road looking north across Great Sand Dunes towards the Crestone Peaks, eastern San Luis Valley, Colorado.  Blanca Peak is about 5 miles to the southeast, behind the photographer.

This photograph is a wonderful image of winds in an approaching storm.

Starting from the top:  there is a thin, very high, sheet of cirro-stratus, the leading edge of the storm.  (Probably around 35,000 feet above sea level.)

Below are numerous layers of moisture evidenced as clouds.  The great white cloud may have begun life as a lenticular but evolved into a lowering cloud mass formed in the crescent of peaks around the San Dunes, as the embrace of those peaks blocked the flow of moisture from the west.  The white cloud is burnished on the top by high winds, and the bottom side is torn by turbulence. 

Below the white cloud are numerous grey clouds that represent fragments showing winds and moisture lifted up the mountain range.  The winds in the photo are from west to east, e.g. from left to right.  As the smaller grey clouds reach a very localized downswirl on the windward sides of the Sangre de Cristos they tend to pile up.

On the far left, west, side of the photo, blowing dust blocks the view north.  The glimpse of sun-dappled floor of the valley shows that the cloud layers are less intense over the center of the valley.

Relatively clear air appears beyond Medano Pass, the one visible mountain pass towards the northeast. The lowering edge of the oncoming storm has reached the mountain barrier but not yet flowed across it.”