Detailed Accident Report
Submitted By: Scott Schmidt; GNFAC
Place: East Fork of Targhee Creek
Summary: 1 snowmobiler caught, buried, and killed wearing a transciever.
TARGHEE CREEK AVALANCHE FATALITY
22 March 2002
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.
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.
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.
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.
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 email@example.com.
Gallatin National Forest Avalanche Center
25 March 2002