From the Summit County Citizens Voice (Bob Berwyn):
Combined, Keystone, Breckenridge and Arapahoe Basin are pitching in $75,000 to help pay for the installation of five new silver iodide generators and two months of operations, with an option to extend the deal for a third month at a cost of $20,000. Vail has been cloud-seeding for more than 30 years, but this the first time Summit County ski resorts have been directly targeted by the program, which is part of a larger regional effort to increase winter snowfall and spring runoff…
The state permitting process addresses environmental and public safety concerns with triggers that require a cessation of cloud-seeding in certain conditions, For example, when parts of Colorado were under a blizzard warning during the Thanksgiving weekend, cloud seeding stopped…
The Summit County cloud-seeding program involves manually operated ground-based generators that release silver iodide particles into the atmosphere when conditions are favorable for precipitation. The particles help provide additional seed material for snow crystal formation. By some commonly accepted estimates, the process can increase precipitation by 5 to 15 percent.
More cloud-seeding coverage here.