"The avalanche appears to have slid on weak, faceted crystals in snow that fell in October and November. Early-season snow can undergo metamorphosis during extended dry periods to form crystals with different shapes called facets or depth hoar that are not able to support as much weight as other types of snow crystals. These weak layers can cause significant, persistent avalanche problems in the early season, and the Bridger-Teton Avalanche Center has identified persistent weak layers as a problem since Christmas."
"The Jackson Hole Ski Patrol reported that this avalanche was triggered by snow pushed off the tram dock by the snowcat. The weight of the falling snow could have provided a much more powerful trigger than the 30-pound bombs did, or could have fallen in just the right place. A 30-pound bomb may seem like a lot, but it can be extremely difficult for explosives to trigger avalanches involving deeply buried weak layers."
A massive avalanche occurred just outside the ski area boundary while a snowcat was clearing snow from the top tram terminal on Rendezvous Mountain, Wyoming. The crown averaged 8 feet in thickness and reached up to 10 feet in places. Two 30-pound bombs had been used the day before to intentionally trigger the slide path without effect. The slide appears to have occurred on weak, faceted crystals from October and November that metamorphosed into facets or depth hoar during extended dry periods. Deep, persistent weak layers have been identified as a problem since Christmas and can be very difficult to trigger with explosives, while loading from falling snow pushed by a snowcat can provide a more powerful or precisely placed trigger. The event represents an uncommon post-control avalanche condition that added to an already busy Teton avalanche season.
Read at SnowBrains
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