City Cast

It's Almost Time for Cloud-Seeding

Scott Dickensheets
Scott Dickensheets
Posted on November 7
Photo of storm clouds.

You need the right storm cloud to engage in cloud-seeding. (Leonid Korchenko/Getty

Back in spring, amid the coverage of the previous season’s glorious snowpack and the wet months that followed, the practice of cloud-seeding was credited for as much as 10% of the snowpack in some parts of the Spring Mountains. While that extra water probably never made it to your faucet, it did help those thirsty ecosystems — including Red Rock Canyon.

As winter — prime cloud-seeding time — approaches, it’s a good time to ask, what is cloud-seeing? Here’s what it’s not: weather manipulation. “Obviously, we don't steer the storms,” says atmospheric scientist Frank McDonough, the Desert Research Institute’s cloud-seeding director. It’s more like an assist. “We just wait for (storms) to come by, and … we make them a little more efficient with their precipitation.”

The process involves getting tiny particles of silver iodide into stormy winter clouds. Some programs use planes; DRI employs ground-based generators. They throw out tiny crystals of silver iodide, which are then carried into the clouds by the storm's updrafts. Each particle attracts water, which then freezes and falls as snowflakes. What makes it work is that silver iodide creates snowflakes at a higher temperature than nature does — as much as 10 degrees warmer.

The right kinds of storm clouds happen in winter, and not often. Last year’s seven seeding efforts was considered “really good,” according to McDonough. When the conditions are right, he generators typically run for 3-10 hours at a time, and seed about a 40-square-mile area. Last year, he adds, cloud-seeding accounted for around 5,500 acre-feet of additional snowfall.

Of course, as with all things, cloud-seeding is not without its political complications.

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