19-20

Thin natural wind slabs in Cooke City

COOKE CITY
Cooke City
Code
SS-N-R1-D1
Aspect
E
Latitude
45.02020
Longitude
-109.93800
Notes

From email (1/30/2020): "2 natural avalanches that ran last night, just west of Cooke City.  Both slides were on easterly aspects around 9500'."

Number of slides
2
Number caught
0
Number buried
0
Avalanche Type
Soft slab avalanche
Trigger
Natural trigger
R size
1
D size
1
Problem Type
Wind-Drifted Snow
Images
Cooke City Wind Slab #2
Cooke City wind slab #1
Slab Thickness units
centimeters
Single / Multiple / Red Flag
Multiple Avalanches
Advisory Year
19-20

Large Natural Avalanche on Fan Mtn.

Fan Mountain
Northern Madison
Code
G
Aspect
N
Latitude
45.29810
Longitude
-111.52400
Notes

 

From email: "There was a large avalanche on the north face of Fan.  It is not on the NE Face that everyone skis, but out to the west of the north couloir where there is a major ridge off the summit.  North aspect, estimated at over 1K ft. wide, to the ground with a deep crown.  Likely triggered by cornice fall."

Number of slides
1
Number caught
0
Number buried
0
Bed Surface
G - Ground
Slab Width
1000.00ft
Slab Thickness units
centimeters
Single / Multiple / Red Flag
Single Avalanche
Advisory Year
19-20

We triggered this avalanche of wind-drifted snow as we approached very carefully from a low angle slope above, on 1/30/2020. This is near Lulu Pass outside Cooke City on a south facing slope at 10,000'. It broke within recently drifted snow, but these slabs could be enough weight to break deeper and wider on sugary layers deep in the snowpack. Photo: GNFAC

Avalanche Details: Human triggered wind slab on Lulu
Cooke City, 2020-01-30
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    • We triggered this avalanche of wind-drifted snow as we approached very carefully from a low angle slope above, on 1/30/2020. This is near Lulu Pass outside Cooke City on a south facing slope at 10,000'. It broke within recently drifted snow, but these slabs could be enough weight to break deeper and wider on sugary layers deep in the snowpack. Photo: GNFAC

    Avalanche Details: Human triggered wind slab on Lulu
    Cooke City, 2020-01-30
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    • Human triggered wind slab on Lulu

    Lulu Pass
    Cooke City
    Code
    SS-AFr-R2-D2-S
    Elevation
    10000
    Aspect
    S
    Latitude
    45.07090
    Longitude
    -109.95800
    Notes

    We triggered this avalanche of wind-drifted snow as we approached very carefully from a low angle slope above, on 1/30/2020. This was near Lulu Pass outside Cooke City on a south facing slope at 10,000'. It broke within recently drifted snow, but these slabs could be enough weight to break deeper and wider on sugary layers deep in the snowpack. I initially approached where the cornice was a little steeper (no overhang though), and then I got that funny feeling and backed off and went to safer feeling spot with the intention to dig at the top of the slope. It broke within the recent snow/wind load, and did not step down. It was about 100’ wide x 70’ long x 2-3’ deep.

    Number of slides
    1
    Number caught
    0
    Number buried
    0
    Avalanche Type
    Soft slab avalanche
    Trigger
    Foot penetration
    Trigger Modifier
    r-A remote avalanche released by the indicated trigger
    R size
    2
    D size
    2
    Bed Surface
    S - Avalanche released within new snow
    Problem Type
    Wind-Drifted Snow
    Slab Thickness
    24.0 inches
    Vertical Fall
    50ft
    Slab Width
    100.00ft
    Weak Layer Grain type
    Decomposing and Fragmented precipitation particles
    Weak Layer Hardness
    4F
    Slab Layer Grain Type
    Wind Broken precipitation particles
    Slab Layer Hardness
    4F+
    Images
    Lulu Crown Profile - 30 Jan
    Human triggered wind slab on Lulu 3
    Human triggered wind slab on Lulu 2
    Crown of human triggered avalanche near Lulu
    Human triggered wind slab on Lulu
    Snowpit in crown of human triggered avalanche on Lulu
    Attached Videos
    Human triggered wind slab on Lulu
    Slab Thickness units
    inches
    Single / Multiple / Red Flag
    Single Avalanche
    Advisory Year
    19-20

    We triggered this avalanche of wind-drifted snow as we approached very carefully from a low angle slope above, on 1/30/2020. This is near Lulu Pass outside Cooke City on a south facing slope at 10,000'. It broke within recently drifted snow, but these slabs could be enough weight to break deeper and wider on sugary layers deep in the snowpack. Photo: GNFAC

    Avalanche Details: Human triggered wind slab on Lulu
    Forecast link: GNFAC Avalanche Forecast for Fri Jan 31, 2020
    Cooke City, 2020-01-30
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