http://www.flygliders.com/landmark_of_soaring.htm

The Marfa Dew Point Front: This is the “dry line” that separates the moist air of the Gulf of Mexico, 600 miles to the east, and the dry air of the deserts of northwestern Mexico and the southwestern United States. The convergence effect of this dry line can generate thermals early in the day, forming a convective cloud street that extends into the Midwestern states of Kansas, and Nebraska.

Thanks to Michael Grisham.