Interesting clouds moved over northwest Kansas, southwest Nebraska, and eastern Colorado during the afternoon of May 28, 2011. These clouds formed in long bands and were spaced every mile or so. These clouds were formed by waves in the middle part of the atmosphere. Where air was acending in the wave, the clouds formed. Where air then descended in the wave, the clouds dissipated. While it is not unusual to observe clouds like these, the length of the bands were longer than normal.
The Goodland radar detected these clouds. See the "rolls" in the following radar imagery.