A long term winter orographic cloud seeding program conducted in central and southern Utah

North American Weather Consultants (NAWC), a subsidiary of the TRC Environmental Corporation, has conducted a wintertime cloud seeding program in Utah during most years since 1973-74. The goal of this program has been to augment the snowfall in the mountainous regions in central and southern Utah. Additional surface runoff that results from this program is utilized primarily for irrigation of farm lands during the summer months.This program relies primarily upon a network of ground based silver iodide generators sited upwind of the mountain barriers. Seeding operations are directed from a central forecast facility in Salt Lake City.An evaluation of this program has been based upon high elevation precipitation and snowpack measurements. A target/control regression prediction analysis based on these measurements indicate approximately a 15 percent increase in precipitation over the target area for the seeded seasons.