Observation: Hatcher Pass

Location: Marmot

Route & General Observations

We went to investigate the crown of the recent human triggered avalanche that occurred on Feb 15th.

Contact, Location & General Observations
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Forecaster Comments

The location where the avalanche was triggered is significantly shallower, more faceted, and has a stout melt freeze crust on top of depth hoar near the ground that does not exist in other locations. The slab was barely cohesive enough to act as a slab and appeared cross loaded from winds on 2/14. We observed pockets of wind slab with pole tests on nearby and adjacent slopes with a similar aspect and elevation.
It is also important to note that we have NOT found any buried facets or had propagation in our pits in other locations for weeks.

Red Flags
Red flags are simple visual clues that are a sign of potential avalanche danger. Please record any sign of red flags below.
Obvious signs of instability
Recent Avalanches?No
Collapsing (Whumphing)?No
Cracking (Shooting cracks)?Yes
Observer Comments

Small shooting cracks on cross loaded gullies. The snow seemed to be less reactive than on Wednesday.

Weather & Snow Characteristics
Please provide details to help us determine the weather and snowpack during the time this observation took place.

Today the visibility was poor with the incoming storm. The intensity of the snowfall increased throughout our tour with about 1 inch of accumulation.

Snow surface

We observed low density snow surfaces as we were touring today. Near ridge tops the snow had very slight signs of being wind affected.


The snowpack where the human triggered avalanche occurred on Feb 15th was significantly thinner than surrounding areas. On near by slopes we observed a snowpack over 4 feet deep. Where the avalanche occurred the snow pack was only 1.5 feet deep. The thin snowpack is likely from a previous avalanche or being stripped by the dec 25th wind event. The avalanche failed on a one finger facets sitting on top of a pencil hard melt freeze crust. This crust was extreme smooth and created a textbook bed surface. This snowpack structure where this avalanche occurred is likely only found in isolated areas. All tests failed at the interface between the 1F facets and the pencil hard melt freeze crusts.

The avalanche was 80 feet wide, with the crown averaging 1.5 feet deep.

Marmot SSW 4100'
40 degree slope
HS 50cm

ECTP24 10cm from the ground on 1F facets failing on a meltfeeze crust
ECTP25 10cm from the ground on 1F facets failing on a meltfeeze crust

Photos & Video
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