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Missoula Avalanche

Public Observation

Observation Details

Observation Date:
February 5, 2022
Submitted:
February 5, 2022
Zone or Region:
Activity:
Skiing/Snowboarding
Location:
Lolo Pass, 46°37’34.5”N -115°25’3.3”W

Signs of Unstable Snow

Did you see shooting cracks? 
No
Did you experience collapsing or whumpfing? 
Yes, Isolated

Observations

Splitboarding from Lolo Pass on 2/5. Toured from the visitors center up alongside the snowshoe track to what is known locally as 'Hamburger Hill'. Dug a pit on a Southeast aspect, just below the ridgeline at 5600 ft. Digging easily exposed a visible layer at roughly 10 cm that was responsible for slight collapsing felt on the way up. Isolated for ECT and performed test. On the third tap from the shoulder, two cracks appeared and propagated the length of the column in the same blow, one at roughly 35 cm of depth, the other at roughly 45 cm. After ECT was completed, shovel shear was implemented, exposing a Q1 shear on the layer at 35 cm. Shovel length limited shear potential and analysis at lower depths. Chose to limit our tour to low-angle terrain, especially considering continued snowfall and sustained winds.

Media

ECTP 1 down ~ 10 cm, ECTP 23 down ~ 35 cm, ECTP 23 down ~ 45 cm
ECTP 23 down ~ 35 cm
ECTP 23 down ~ 45 cm
Shear Sudden Planar Q1 at ~35 cm
Shear Sudden Planar Q1 at ~35 cm
Buried Depth Hoar appears responsible for Q1 shear

Advanced Observations

Observed Avalanche Problem #1: 
Persistent Slab
Comments: 
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