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Professional Observation

Basic Information

Observation Details

Observation Date:
February 6, 2023 - February 7, 2023
Submitted:
February 7, 2023
Observer:
PAC - Kevin Studley
Zone or Region:
Council Mountain Area
Location:
North of Council Mountain

Signs of Unstable Snow

Recent Avalanches? 
Yes
Cracking? 
None Experienced
Collapsing? 
None Experienced
Recent avalanche activity observed just under ridgelines above 8000' on NE aspects. Multiple snowmobile-triggered avalanches on a layer of buried surface hoar around 7400' on NE aspects.

Snow Stability

Stability Rating: 
Fair
Confidence in Rating: 
Moderate
Stability Trend: 
Steady

Media

Crown profile
Snowmobile-triggered avalanche Monday (02/06). SS-AMu-R2-D1-7500'-N/NE
Snowmobile-triggered avalanche near Council Mtn Monday (02/06). HS-AMu-R3-D2-7340'-N/NE. This avalanche ran on a layer buried surface hoar, ranged in depth from 40-110 cm (16-44
Snowmobile-triggered avalanche near Council Mtn Monday (02/06). HS-AMu-R3-D2-7340'-N/NE. This avalanche ran on a layer buried surface hoar, ranged in depth from 40-110 cm (16-44
Snowmobile-triggered avalanche near Council Mtn Monday (02/06). HS-AMu-R3-D2-7340'-N/NE. This avalanche ran on a layer buried surface hoar, ranged in depth from 40-110 cm (16-44
Snowmobile-triggered avalanche near Council Mtn Monday (02/06). HS-AMu-R3-D2-7340'-N/NE. This avalanche ran on a layer buried surface hoar, ranged in depth from 40-110 cm (16-44
Snowmobile-triggered avalanche near Council Mtn Monday (02/06). HS-AMu-R3-D2-7340'-N/NE. This avalanche ran on a layer buried surface hoar, ranged in depth from 40-110 cm (16-44
Snowmobile-triggered avalanche near Council Mtn Monday (02/06). HS-AMu-R3-D2-7340'-N/NE. This avalanche ran on a layer buried surface hoar, ranged in depth from 40-110 cm (16-44
Two snowmobile-triggered avalanches and one natural avalanche near Council Mtn Monday (02/06).
Snowmobile-triggered avalanche near Council Mtn Monday (02/06). HS-AMu-R3-D2-7340'-N/NE. This avalanche ran on a layer buried surface hoar, ranged in depth from 40-110 cm (16-44

Advanced Information

Weather Summary

Cloud Cover:
Overcast
Temperature:
N/O
Wind:
Light , NW

12-16" of new snow within previous 24 hours. Moderate SW winds for nearly 72 hours (Friday-Sunday).

Avalanche Observations

 #  Date Location Size Type Bed Sfc Depth Trigger Comments Photo
1 Past 24 hours Near Council Mountain
NE 7340 		D2 HS O-Old Snow 2.5' AM-Snowmobile
u-Unintentional 		None
2 Past 24 hours Near Council Mountain
NE 7500' 		D1 SS I-New/Old Interface 18" AM-Snowmobile
u-Unintentional 		None

Four recent avalanches observed yesterday near Council Mountain. Several small, wind slab avalanches observed (not pictured here). At least three of the four avalanches were snowmobile-triggered. Most all of them were about 7400', NE aspect, on slopes between 30-35 degrees. PAC investigated one of the snowmobile-triggered avalanches to find a layer of buried surface hoar as the weak layer.

Snowpack Observations

The PAC dug a snowpit earlier in the day on a W aspect at 7410'. CT 11 RP (x2) ECTN 15 29 cm down FCxr. CT 15 RP CT 22 RP 75 cm down SH ECTX. When we were riding out we noticed a small snowmobile-triggered avalanche on a slope adjacent to where we dug this snow pit.

See Snow pilot photo for a crown profile of the larger snowmobile-triggered avalanche.

The interesting thing about these results from our stability tests is that this buried weak layer responsible for these avalanches is not propagating in ECT. It fails moderately in CT and less than 50 cm on PST, however it has not shown propagation in ECT.

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