Forest Service study focuses on wet slab avalanches
December 21, 2005
SUMMIT COUNTY – Forest Service avalanche personnel are setting up a comprehensive study of wet slab conditions that could give ski resort snow safety workers more tools to evaluate and forecast dangerous conditions.The study, involving ski areas and Forest Service facilities across the western United States, was spurred by the fatal avalanche at Arapahoe Basin last spring, when a wet slab released near the top of Palivacinni’s First Alley swept David Conway to his death in the dense timber below.After releasing a report on the slide that showed A-Basin had followed all required and established snow safety protocols, the Forest Service also said it would intensify efforts to understand the dynamics of wet slab avalanches.”The premise behind the study is that wet slabs are the most poorly understood avalanches,” said Doug Abromeit, director of the agency’s Idaho-based national avalanche center. “Hopefully we’ll develop a better feel and better methodology for forecasting wet slabs.” Abromeit said the agency’s avalanche experts “beat the bushes” to find the needed instrumentation but haven’t been able to come up with any funding specifically for this research project. The seven sites included in the study represent the three major climate/snowpack regimes used by avalanche forecasters, including maritime (coastal ranges), continental (interior Rocky Mountain ranges with dry snow and cold temperatures) and inter-mountain (sharing characteristics of both). The research is geared toward understanding the dynamics between snow structure and warming spring temperatures, Abromeit said. Part of the work will include remote temperature sensors in the snowpack to relay data automatically. “We know about crusts sitting on top of faceted snow, but the behavior is unpredictable in the spring,” Abromeit said. “How long does it have to be above freezing? We’re trying to find trends and patterns that can help us understand what triggers them. “It’s not always at the spike of the temperatures,” he added, outlining some of the mysteries still associated with wet slab releases like the unexpected avalanche at A-Basin.”We want to improve our understanding of the snowpack changes in spring,” said Dillon District ranger Rick Newton. “Hopefully that will help us predict and minimize the risk associated with that.”Abromeit said one reason little is known about wet slab behavior is because most ski areas close in the spring before those conditions exist. But for late season venues like A-Basin, that added understanding could help ski patrollers maintain safe conditions.