22-23

Whumpf, propagating test result

Sheep Creek
Cooke City
Code
Latitude
45.03440
Longitude
-109.98400
Notes

skied both NE, S and SW aspect lines in Sheep Creek Basin. No signs of wind loading where we traveled, up to 9600’ at the saddle between Sunset and Miller Mountain. There were light winds (M gusts). 8-10” of new low density snow.

Dug a pit on a SW aspect, 8480’:

160cm deep

CT22Q2 Down 40, EctN 25 down 40

ECTP28 down 85

Pole probing confirmed the presence of the top persistent grain layer throughout the landscape, although the associated crust was not widespread. 

We also experienced a Whumpf at 45.03667, -109.96733 On a SW slope, 9000’ in a shallow area (125cm depth). 

Number of slides
0
Number caught
0
Number buried
0
Snow Observation Source
Whumpf, propagating test result
Slab Thickness units
centimeters
Single / Multiple / Red Flag
Red Flag
Advisory Year
22-23

Snowmobile triggered slab in Lionhead

Lionhead Ridge
Lionhead Range
Code
HS-AMu-R2-D2.5-O
Elevation
8800
Aspect
E
Latitude
44.71450
Longitude
-111.31800
Notes

On the way back to Lionshead.  Came upon this recent avalanche.  Rushed up to the group of 4 guys.  They were fine, not the guys who set it off.  The group of 6 we passed going there set it off.  The group of 4 said they saw these guys ... all on the hill at same time, stuck and climbing around the stuck guy.  All were okay but I hear one guy was shaken up. 4-5ft deep at break by 200-300ft wide, ran 400+ft.

Number of slides
1
Number caught
0
Number buried
0
Avalanche Type
Hard slab avalanche
Trigger
Snowmobile
Trigger Modifier
u-An unintentional release
R size
2
D size
2.5
Bed Surface
O - Old snow
Problem Type
Persistent Weak Layer
Slab Thickness
48.0 inches
Vertical Fall
300ft
Slab Width
250.00ft
Images
Lionhead avalanche distance
Lionhead avalanche 1
Attached Videos
Don't Get Complacent - Lionhead - 2 January
Snow Observation Source
Lionhead avalanche
Slab Thickness units
inches
Single / Multiple / Red Flag
Single Avalanche
Advisory Year
22-23

On the way back to Lionhead.  Came upon this recent avalanche.  Rushed up to the group of 4 guys.  They were fine, not the guys who set it off.  The group of 6 we passed going there set it off.  The group of 4 said they saw these guys ... all on the hill at same time, stuck and climbing around the stuck guy.  All were okay but I hear one guy was shaken up. 4-5ft deep at break by 200-300ft wide, ran 400+ft. Photo: T. Anafarta

Avalanche Details: Snowmobile triggered slab in Lionhead
Forecast link: GNFAC Avalanche Forecast for Sun Jan 1, 2023
Lionhead Range, 2023-01-01
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    • On the way back to Lionhead.  Came upon this recent avalanche.  Rushed up to the group of 4 guys.  They were fine, not the guys who set it off.  The group of 6 we passed going there set it off.  The group of 4 said they saw these guys ... all on the hill at same time, stuck and climbing around the stuck guy.  All were okay but I hear one guy was shaken up. 4-5ft deep at break by 200-300ft wide, ran 400+ft. Photo: T. Anafarta

    Avalanche Details: Snowmobile triggered slab in Lionhead
    Forecast link: GNFAC Avalanche Forecast for Mon Jan 2, 2023
    Lionhead Range, 2023-01-01
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    • On 12/31 we saw an avalanche that appeared very recent, and likely triggered by a snowmobiler. It was on a west facing slope at 10,000', and was a hard slab 1-4 feet deep and 100' wide, ran about 200' vertical. AMu-HS-R3-D2-O. This was a clear sign that weak layers exist, especially where the snowpack is relatively shallower, and recent snow has been drifted into thick slabs that are unstable over this weak snow. Photo: GNFAC

     

    Avalanche Details: Snowmobiler triggered hard slab avalanche Sheep Mtn.
    Forecast link: GNFAC Avalanche Forecast for Mon Jan 2, 2023
    Cooke City, 2023-01-01
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    • On 12/31 we saw an avalanche that appeared very recent, and likely triggered by a snowmobiler. It was on a west facing slope at 10,000', and was a hard slab 1-4 feet deep and 100' wide, ran about 200' vertical. AMu-HS-R3-D2-O. This was a clear sign that weak layers exist, especially where the snowpack is relatively shallower, and recent snow has been drifted into thick slabs that are unstable over this weak snow. Photo: GNFAC

     

    Avalanche Details: Snowmobiler triggered hard slab avalanche Sheep Mtn.
    Forecast link: GNFAC Avalanche Forecast for Sun Jan 1, 2023
    Cooke City, 2023-01-01
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    • Snowmobiler avalanche fatality on Crown Butte

    Crown Butte
    Cooke City
    Code
    HS-AMu-R4-D3-O
    Elevation
    9800
    Aspect
    SE
    Latitude
    45.05250
    Longitude
    -109.96200
    Notes

    On December 31, 2022 a snowmobiler was killed in a very large avalanche north of Cooke City, MT. The avalanche occurred near Daisy Pass on Crown Butte on a southeast facing slope at 9,800’. Two brothers (age 17 and 21) from Washington were snowmobiling uphill on adjacent slopes. The older brother was climbing a steeper slope and triggered the avalanche 100-200’ below the top. He was carried 600 vertical feet and buried 5 feet deep. The buried rider was wearing an airbag pack that was not deployed. Both riders had shovels and probes. They were not wearing avalanche beacons. A nearby group of riders rode up to the slide within minutes after it happened, saw a buried snowmobile and began to search for the rider. One rider from that group went into Cooke City to alert Search and Rescue. The buried rider was located with a probe line an hour after the avalanche happened. He was unable to be revived with CPR and AED at the site. The avalanche appeared to be 2-4' deep, 500' wide, 600' vertical, and broke on weak snow near the bottom of the snowpack. AMu-HS-R3/4-D3-O

    Our deepest condolences go out to the family, friends, and those involved.  

    Full report available here: http://www.mtavalanche.com/accident/22/12/31

     

    Number of slides
    1
    Number caught
    1
    Number buried
    1
    Number killed
    1
    Avalanche Type
    Hard slab avalanche
    Trigger
    Snowmobile
    Trigger Modifier
    u-An unintentional release
    R size
    4
    D size
    3
    Bed Surface
    O - Old snow
    Problem Type
    Persistent Weak Layer
    Slab Thickness
    24.0 inches
    Vertical Fall
    600ft
    Slab Width
    500.00ft
    Weak Layer Grain type
    Faceted Crystals
    Weak Layer grain size
    1.50mm
    Weak Layer Hardness
    4F
    Slab Layer Grain Type
    Decomposing and Fragmented precipitation particles
    Slab Layer Grain Size
    0.30mm
    Slab Layer Hardness
    P-
    Images
    Full view of Crown Butte avalanche
    View down path on Crown Butte
    Looking up to crown on Crown Butte
    Debris of avalanche on Crown Butte
    Crown of avalanche fatality on Crown Butte
    Crown Butte sled in debris
    Crown Butte Profile - 1 Jan 2023
    Crown Butte avalanche fatality - crown
    Crown Butte avalanche fatality - up from burial location
    Crown Butte avalanche fatality - full slide
    Attached Videos
    Snowmobiler avalanche fatality, Cooke City - 31 Dec 2022
    Snow Observation Source
    Snowmobiler avalanche fatality on Crown Butte
    Slab Thickness units
    inches
    Single / Multiple / Red Flag
    Single Avalanche
    Advisory Year
    22-23

    On December 31, 2022 a snowmobiler was killed in a very large avalanche north of Cooke City, MT. The avalanche occurred near Daisy Pass on Crown Butte on a southeast facing slope at 9,800’. The avalanche appeared to be 2-4' deep, 500' wide, 600' vertical, and broke on weak snow near the bottom of the snowpack. Photo: GNFAC

    Avalanche Details: Snowmobiler avalanche fatality on Crown Butte
    Cooke City, 2023-01-01
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