Avalanche Accident Report          Forest Service Utah Avalanche Center

 

Wednesday, February 21, 2007

 

Gobblers Knob – Solo ski tourer caught, carried and killed by trauma

 

Accident Report by Drew Hardesty and Brett Kobernik    2-22-07 9pm

 

Location:

The avalanche was on a steep northeast facing slope at 10,000’ off the south ridge of Gobbler’s Knob.  The terrain drains into Butler Basin above the East Butler Fork of Big Cottonwood Canyon.  See topographic map. Photos.

 

Accident and Rescue Summary:

A party of three experienced backcountry skiers from Norway, familiar with the Wasatch terrain, set out for a day of ski touring in the Gobblers Knob/Mt. Raymond area.  According to reports, the victim, seeking more challenging terrain, left his two partners at the Gobblers/Raymond divide and continued to the summit of Gobbler’s Knob with the plan to meet back at the trailhead within the hour.  After waiting at the car for some time, the remaining two called 911 to initiate a search.  A helicopter with personnel using night vision goggles verified tracks going into an avalanche high on the peak with none coming out.  The body recovery efforts by both Salt Lake Country Search and Rescue and Wasatch Backcountry Rescue began the following morning. The three Norwegians were all wearing rescue gear and had called the avalanche forecast that morning.  The Utah Avalanche Center had rated the danger as  “CONSIDERABLE on slopes steeper than about 35 degrees facing northwest through northeast through southeast, where dangerous avalanches 1 to 3 feet deep can be triggered by people.”  The forecaster, weary of the three previous fatalities that week, implored people to “Back off the steep stuff – if the close calls continue, someone else is going to get killed or hurt.” 

 

Terrain Summary:

The area of the avalanche is not a classic descent off the peak and it is unknown whether the skier had intended to ski it or whether he was traversing across the starting zone to gain another ridge.  A descent would have taken you a few hundred feet through some trees with some wandering to avoid some sections of cliffband.  The south ridge of Gobblers is a steep, often corniced ridgeline with avalanche paths falling off both to the east and the west.  Descending tourers are generally forced off parts of the ridge as sections of it are rocky and knife-edged.  In the big picture, ridges are known to be areas of safety unless A: the ridge becomes steep and rounded, becoming in essence, terrain capable of producing a slide; or B: the terrain forces you off the ridge into a starting zone.  Under certain circumstances, it may be warranted to remove skis or board and boot up or down through these features.

 

Avalanche Data: 

The avalanche would be classified as a HS-AS-R4D2-O, a hard slab avalanche artificially (and unintentionally) triggered by a skier.  The slope angle ranged from 35-40 degrees, with an average of 37 degrees.  The crown depth ranged from 18” at the trigger point to 24” along the eastern end of the fracture line.  The slide measured 250’ wide, running over 600’ vertical down the slope.  The victim was found in some trees a third of the way down the slope, with trauma being the cause of death.  The ‘one-finger hard’ wind slab failed on very weak, cohesionless 3-4mm depth hoar in an area with a total depth of snow of 36-40”.  Of interest is the initial slide sympathetically triggered another slide with similar snowpack structure off to skier’s right, pulling out 2’ deep and 100’ wide.  This slide stepped down to some older buried intact surface hoar, formed earlier in the month.  

 

Weather and Avalanche History: 

Early season drought produced one of the thinnest and weakest snowpacks in years.  17” of snow with moderate winds warranted an Avalanche Warning with a HIGH danger on February 11th and 12th, with the danger remaining at Considerable or higher through the day of the incident.  Another storm on the 19th brought 13” of snow with moderate to strong southwesterly winds, resulting in another localized natural cycle and a number of close calls.  Since the 11th, the Utah Avalanche Center heard about 25 unintentionally triggered avalanches with nearly half of those catching and carrying people down the slope.  Many of the run-ins were with individuals oblivious to the dangers of avalanches while others were with some who have been highly trained or had years of experience.