I've been there. You've got a big valley to the west, the only desert in Colorado, and a very high, steep mountain range with one low spot. The winds blow across the valley, pick up sand, and then drop it as they are funnelled to the low spot and lifted upwards.
Some of the dunes are 700 feet high.
The winds blow across the valley, pick up sand, and then drop it as they are funnelled to the low spot and lifted upwards.I was there in the winter (it was probably in the 50s) and went for a hike in the dunes. I had to beg some fellow hikers for some lip balm before my lips cracked off in the cool, strong, and extremely dry wind.