This animation of GOES-12 6.5 micrometer "water vapor" (channel 03) images shows a lee-side frontal gravity wave that was propagating southward along the foothills of the Rocky Mountains and the High Plains in eastern New Mexico and western Texas on 03 April 2007. The shift to northeasterly surface winds (red barbs) is evident as a cold frontal boundary moved southward through the region. Note how the vertically-propagating gravity wave appears to initiate the formation of cirrus cloud patches along the foothills in eastern New Mexico.