Monday, February 27, 2012

Secondary Slides; Elevation Effects

While checking to see if the NWAC Alpental report was available yet, I noticed a report for a 2011 incident on the same mountain as the recent Stevens Pass incident (although different aspect)

Excerpted below are two passages that I found especially interesting.

First, the danger of secondary slides to rescuers:
“After patrol examined him with a portable AED and administered CPR for 15 minutes or so they pronounced him dead. Other patrollers came behind with a toboggan to extract the victim. In doing so they triggered another small wet slide which propagated into the zone we were in and partially buried me and the two patrollers as well as sent my snowboard and one patroller's skis down the hill. One of the other members of our group was able to extract the patrollers and myself." 
Second, the different weather and snowpack conditions at lower elevations:
"The avalanche forecast issued by the NWAC on the day of the event (3/27/01) indicated that for Sunday “increasingly dense snow or rain should further load or weaken the already weak upper 12 to 16 inches of near surface snow and increase the potential for both natural and human triggered loose or wet loose slide activity.”  However, according to the witness account below, the riders were aware of the increasingly wet snow conditions encountered below 4000 feet as they descended toward US 2. Unfortunately a bad landing resulting in a hard turn were enough stress to start a small wet loose slide that subsequently caught and carried the victim into a terrain trap (small stand of trees)." 
"The strong destabilizing effects of even early spring radiation or direct sunshine on recent snow
cannot be overemphasized and should always be considered when descending into lower elevation  terrain that may not have the cooling effects of winds near higher ridges." 

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