Detailed Accident Report

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Date: 2000-12-01
Submitted By: Larry Livingood Jackson Hole Resort
Place: Glory Bowl
State: WY
Country: USA
Fatalities: 1
Summary: 1 snowboarder caught buried and killed

There have been two avalanche deaths in Wyoming this week. On Tuesday, November 28th, the Casper Star Tribune reported the death of Mark Nieson in the Hoodoo Creek area, east of the Continental Divide. The nearest large town is Cody, although the slide occurred pretty deep in wilderness, a 4-5 hour horseback ride away from an open road. He was hunting with an outfitter when he was caught in an avalanche and swept `1000 yds into a valley.` The event is believed to have occurred Monday. The victim died of head and chest trauma. No other details are available at present.

The second event was this morning, December 1st. A snowboarder was caught, carried and buried in Glory Bowl. The slide occurred on a southerly aspect around 8 AM. It ran over 1000'. The estimated 2 foot slab released on a hard crust with faceted snow at the interface (buried surface hoar formed at cold temperatures before the recent snow events). Southerly aspects have been recently loaded by NW winds associated with a clearing trend. The victim was found 15 feet above the road. He was buried under 5 feet of snow. The slide was Class III, covering the road with about 10 feet of desposition.

The victim was one of three in the party. Apparently, he entered the path while his companions were still climbing and out of sight, so the event was unobserved. He was buried for aproximately 1 1/2 hours. Although it was only a 2 foot slab, the slope narrows into a gulley before hitting the road, so the deposition was concentrated. Skies were sunny this morning and temperatures were rising from single digits at the time of the slide.

Natural and triggered activity has been observed on southerly and easterly aspects over the past few days at the ski area and in the backcountry at both mid and upper elevations. The starting zone of the path is above 9000'. Glory Bowl is in the Bridger-Teton National Forest. The highway, which lies in the middle of the path, is artillery maintained by WYDOT. This is a preliminary report...more details later.

REPORT by Don Sharaf

Teton Snow Observations

Glory Bowl Slide Path

December 2, 2000

A group of us took a pre-dawn tour up Mt. Glory this morning. We went to investigate the avalanche that killed a snowboarder yesterday morning (12/01/00). It was a large avalanche that took out the entire skier?s right side of the Bowl (ESE to NNE aspects) and ran from 10,000? to 7860?where it crossed Highway 22. Deposition below ?the gut? was three to four meters deep (10?-13?) and the terminus made it over the highway.

Subsequent artillery work on Twin Slides and the intact portion of Glory Bowl didn?t bring out any more avalanches (though it may have increased the crown length of the existing avalanche).

Classification: SS-AD-3-O (using both the Canadian and U.S. size scales)

TERRAIN: The path funnels from a large bowl into a narrow rocky chute(?The Gut?) with several small cliff bands on the way. Glory Bowl defines the phrase ?terrain trap.?

Aspect: ESE to NNE

Runout Angle: 29?

Starting Zone Angles: 34?? 44?

Vertical Run: 2140? (652m)

Horizontal run: 3800? (1159m)

Crown Length:1500? (457m)

SNOWPACK: Overall, there was shallow snowpack with a good amount of variation in snow depth and strength. The avalanche bed surface was a crust layer from the early part of November (there is also a crust from latter October, which in some areas the avalanche may have scoured down to). The crust?s hardness varied with snow depth (shallower areas having weaker crusts). The failure layer was a layer of variable thickness that was composed of 2-4mm depth hoar. The size of the depth hoar varied with total snow depth (deeper areas having smaller grains), but the facets were well developed and striations were easily visible. Some locations had thin slabs of 1 finger hardness, but the majority of the overlying snow was fist and four finger hardness facets, graupel, and decomposing/fragmenting snow grains. I did not observe any surface hoar in any of the pits that I dug. Crown depths varied from 20cm to 70cm(8-28?), and the average crown depth was 40cm (16?). Snow depth in the upper starting zone varied from 80-130cm (31-51?).

STABILITY TESTS: None of the stability tests that we did would scream danger if you performed them without any other information. In one deeper location the Stuffblock scores were failing at 60 and 70cm drop heights with average shears (SB60 and SB70 Q2). Rutschblock score was RB6 Q2 (third hard jump at mid block ? clean, but sluggish shear). At shallower locations, the Stuffblock failed at lower drop heights SB20 and SB40 and had clean shears (when the underlying depth hoar didn?t just crush as it failed). The other Rutschblock that we did failed cleanly on the first hard jump at the top of the block ? RB4 Q2. The shear was sluggish and only half of the block failed so we had a hard time assigning the quality of the shear to it.

WEATHER: Abnormally cold temperatures and periodic light snowfalls characterized November weather. On Wednesday night we had a SW flow that came in warm and with strong winds depositing 6? Jackson Hole Ski Area(Raymer Plot) and had lots of graupel associated with it. Yesterday(December 1) was a clear day with moderate temperatures and calm winds. The sun was bright, but probably had not warmed the snowpack too significantly at the time of the avalanche (~0800).

HUMAN FACTORS: There were no witnesses of the avalanche, so some details are sketchy. What I understand from the media reports is that the victim did not have a transceiver. Two other snowboarders arrived at the top very shortly after the avalanche ran (so there were no direct witnesses). The track that entered the bowl was the first and only one following the last snow/wind event, but was not the first tracks made in the bowl this season. The snowboard track started at the center of the bowl, which left no access to escape routes to adjacent ridges. The victim was found under ~2m (6?) of snow with his snowboard damaged, but still attached to his feet.