Detailed Accident Report

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Date: 2002-01-31
Submitted By: Ron Johnson; GNAFC
Place: Lionhead, Near West Yellowstone
State: MT
Country: USA
Summary: 1 snowmobiler caught, buried, and rescued wearing a tranciever

ONE SNOWMOBILER CAUGHT, BURIED AND UNINJUIRED,

NEAR WEST YELLOWSTONE,MONTANA

JANUARY 31, 2002

During the afternoon of January 31, 2002, a snowmobiler released an

avalanche. He and a partner were riding near Lionhead, which is about 15

miles (24 km) northwest of West Yellowstone, Montana. He got stuck

trying to climb a steep, 600-foot (180 m) hill. The avalanche released

about 400 feet (120 m) above him while he was trying to free his sled.

His partner witnessed the avalanche from a small ridge near the bottom

of the avalanche path.

Both riders wore avalanche transceivers and carried shovels. They stated

that they rarely rode on the same slope at the same time, which was the

reason only one person was on the slope. When the ?dust? settled, the

rider who witnessed the avalanche rode onto the debris. He didn?t see

any surface clues and commenced a beacon search. As soon as he turned

his beacon to receive, he acquired a signal. Within a few minutes, he

decided he was close enough to start digging. About ten minutes after

the avalanche, he had dug through about 5 feet of debris and struck his

partners helmet. The buried person, though unconscious was breathing.

The rescuer left the site for several minutes while he used a cell phone

to notify the authorities in West Yellowstone. He returned to the site

and spent another 10 to 15 minutes removing the remainder of the snow

that covered his partner. The buried person regained consciousness after

being buried for a total of about 20 minutes. He remembered being caught

in the avalanche and heard his partner searching for him before he

?blacked out?. He was buried lying on his side, perpendicular to the

slope and wasn?t injured.

The next day, I went to the site and talked to the people involved in

the incident. They were retrieving a snowmobile, which was buried under

5 feet (1.5 m) of debris, at the same elevation and 20 feet (6 m) from

where the rider had been buried. These guys were from Wyoming and had

ridden in this area during previous visits. They were experienced

mountain riders.

The avalanche was about 500 feet (150 m) across and ran about 600

vertical feet (180 m). The crown was at 8400 feet (2520 m) in elevation

and was 2 to 4 feet (.6 to 1.2 m) deep. The avalanche using the U.S.

Classification was HS-3-AV-O. Using the Canadian Scale this was a size 2

to 3 avalanche. The avalanche fractured on a weak layer of faceted

crystals that formed near the snow surface during a cold, dry spell

around Christmas. The average slope angle of the bed surface was 37

degrees.

In summary: A person is alive because his partner watched him ?highmark?

from a safe location, his partner carried and knew how to use the

appropriate rescue gear, and his partner did all ?the right stuff? to

facilitate a successful rescue.

Ron Johnson, Avalanche Specialist, Gallatin National Forest Avalanche

Center, rjohnson@fs.fed.us , 406-587-6984