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Date: 2002-03-22
Submitted By: Scott Schmidt; GNFAC
Place: East Fork of Targhee Creek
State: ID
Country: USA
Fatalities: 1
Summary: 1 snowmobiler caught, buried, and killed wearing a transciever.

****OFFICIAL REPORT****

TARGHEE CREEK AVALANCHE FATALITY

22 March 2002

SYNOPSIS:

One snowmobiler was caught and killed in an avalanche that occurred on

the Montana/Idaho border. The avalanche released on a non-wind-loaded

slope, with a southwest aspect, and a slope angle that averaged 32-35

degrees. The crown was 3 ? 4 feet deep, and 300 feet in width. The

avalanche ran approximately 800 vertical feet, with an a-angle of 24

degrees. US classification of the avalanche is SS-4-AS-O.

WEATHER:

Very little new snow had fallen prior to the avalanche and the slope had

not been recently wind loaded. A storm cycle had deposited 0.7 inches of

water over a period of 5 days just prior to the avalanche. Winds had

been moderate, blowing 10-15 mph from the west, for most of the storm

cycle. The exception was a 24-hour period on the 19th and 20th during

which winds averaged 20-30 mph, with gusts into the 50s, from the

southwest. Temperatures had been exceptionally warm for two days prior

to the avalanche, with daytime highs reaching 48 degrees Fahrenheit on

the 21st, and 53 degrees Fahrenheit on the 22nd. The overnight low the

evening of the 21st was 12 degrees Fahrenheit.

AVALANCHE:

26-year-old Matt Blumer of Pierre, South Dakota was riding with 6

friends in the East Fork of Targhee Creek. It is unclear if the group

rode up the Targhee Creek drainage or dropped into the basin from the

Lionhead ridge. The group started high-marking a southwest-facing slope,

approximately ? mile from several large, natural slides that had

released earlier in the afternoon. Matt triggered the avalanche, at 2:27

pm, as he made a pass above a steep rollover, approximately half way up

the slope. The fracture propagated up hill another 400 vertical feet

above him. The avalanche from the first fracture carried the victim and

his sled through a thin stand of trees at the top of the rollover and

deposited him on a bench at the bottom of the slope. This first wave of

the avalanche was followed by a second wave from the top of the slope

that helped to bury the victim 20 feet deep.

RESCUE:

One member of the party rode out to Targhee Pass and initiated the call

for Search and Rescue. Because the location of the avalanche was not

initially clear, search teams from both Montana and Idaho responded. A

helicopter, with two dog teams, was dispatched from Bozeman, MT and

helped locate the actual site. The members of the victim?s party had

located and recovered the body (at 4:25 pm) using an avalanche

transceiver when search and rescue personnel arrive on-scene.

Resuscitation efforts by members of the victim?s party, and by Search

and Rescue, were unsuccessful.

SNOWPACK:

The avalanche released on a layer of small grained, faceted, crystals

that formed the first week of January. Other slopes in this area had

formed surface hoar during the same period, and the combination of the

two different weak layers had been responsible for two other burials --

in which the victims had been recovered alive -- earlier in the season.

During the first part of March, these layers gain significant strength

and were non-reactive to snowpit stability tests, even after large

loading events. March 2002 had been unusually cold in Montana, so the

warming trend that happened the 20-22 was the first real warm weather

the snowpack had seen all season. Because of the short duration of the

warm spell, very little wet slide activity was recorded, however some

small slab releases were noted on the 22nd in the Cabin Creek drainage

north of the Lionhead area. These small avalanches released on

south-facing slopes that had been wind loaded the previous week, and

only involved the upper 12 inches of the snowpack. The interesting thing

about the Targhee Creek avalanche was the significant number of slopes

that released just within one small basin. In all, 5 large avalanches

released within a half-mile of each other. No other large avalanches are

known to have released anywhere else in the range. It is speculated that

the tight confines of the drainage acted as a reflector oven and

enhanced snowpack heating at the surface. During the snowpack

investigation, conducted on the 23rd, the air temperature had returned

to more seasonal 38 degrees Fahrenheit, under overcast skies, and the

snowpack was again stable.

If you have questions about this incident please feel free to call me at

406-587-6984 or email me at sschmidt@fs.fed.us.

Scott Schmidt

Avalanche Specialist

Gallatin National Forest Avalanche Center

25 March 2002