Triggering Avalanches Ask Dave a weather question

Dave Thurlow, Host

 
Hi, I'm Dave Thurlow from the Mount Washington Observatory and this is The Weather Notebook. Each winter, over 100,000 explosions are triggered across the West. Their purpose? To get unstable snow moving before it moves itself. Today on the show, we're going to discuss some of the ways avalanches are caused, for safety's sake.

Slab avalanche in the Purcell Mountains, BC. Photo: Dr. Bruce Jamieson

Many of these triggered avalanches take placein ski areas, always while the skiers are gone, ofcourse. Typically, a ski patroller takes atwo-pound stick of dynamite or TNT, lights thefuse, and tosses it towards a high-risk avalanchespot -- from above. The fuses have a safetymargin of about two minutes, which gives thepatroller time to ski out of harm's way.

Another technique for triggering slides from adistance is to use surplus military rifles andhowitzers. These are good for triggeringavalanches up to two or three miles away inplaces, that ski patrollers can't safely reach. Allthis may sound like a nerve-racking business, butavalanche control, along with better educationand warnings, have made a big difference in ski-area safety. Since 1986 there hasn't been a single skier killed by an avalanche within the bounds of a U.S. ski area. The bad news is that avalanche deaths from snowmobiles are on the rise. So, as always, it's dangerous for skiers to venture past that "out of bounds" sign, no matter how inviting the snow may look. It's better to knock snow off the mountain sides on purpose, than to have a stray skier do it by accident.

Thanks today to contributing writer Bob Henson. Our show is underwritten by Subaru, the beauty of all wheel drive, with major support provided by the National Science Foundation.