24-25

Remotely Triggered Avalanche Lionhead

Lionhead Ridge
Lionhead Range
Code
SS-AMr-R3-D2-O
Elevation
8600
Aspect
SE
Latitude
44.71450
Longitude
-111.31800
Notes

As we approached our second pit site on the lip of Moto Hill (southeast aspect at 8600'), I stopped and looked back in time to see avalanche debris slamming into the trees on a connected slope below. We remotely triggered the avalanche from 150 feet away. It broke 200' wide and 1-3 feet deep. It ran an estimated 200' vertical feet (based on a slope map. We couldn't safely access the toe of the debris). The avalanche failed on a layer of Fist hard facets. This is interesting because it is these mid-elevation slopes in the LH area that seemed really weak on previous visits to the area. The slope may have some wind-loading, but it was minimal and not the cause of this avalanche. 

We dug a pit on an east aspect around the corner and down from Airplane Bowl (before the avalanche) and found a similar snowpack setup. 150 cm of total snow and half was composed of weak facets. ECTP22 and P24 on the mid-pack January layer of Fist hard facets and surface hoar

Take Homes: 

  1. Lionhead seems to be the epicenter of persistent slab instability. It is the weakest I have seen. Southern Madison and Southern Gallatin seem to be similar and I would group them together when describing conditions. 
  2. Mid-elevation slopes are thin and weak and can clearly avalanche. This is problematic because many folks play in lower elevation terrain when conditions are dangerous... While small compared to the upper bowl, the avalanche we triggered would have been deadly. It was deep and it would have strained its victim through trees. 
  3. We heard about a similar remote-triggered avalanche in Black Canyon today. This has me nervous that I missed something in the Centennials. While we didn't see anything too concerning there yesterday outside of wind-loaded slope, I am not happy about two remotely triggered slides less than 20 mile away. 
Number of slides
1
Number caught
0
Number buried
0
Avalanche Type
Soft slab avalanche
Trigger
Snowmobile
Trigger Modifier
r-A remote avalanche released by the indicated trigger
R size
3
D size
2
Bed Surface
O - Old snow
Problem Type
Persistent Slab
Slab Thickness
24.0 inches
Vertical Fall
200ft
Slab Width
200.00ft
Weak Layer Grain type
Faceted Crystals
Weak Layer grain size
3.00mm
Weak Layer Hardness
F
Snow Observation Source
Slab Thickness units
inches
Single / Multiple / Red Flag
Single Avalanche
Advisory Year

Remotely Triggered Avalanche Lionhead

Date
Activity
Snowmobiling

Mark, Dave and Brian DiLenge from IDPR rode up Denny Creek and out across below Lionhead Ride. Fog and low clouds made visibility tough but we bounced along the treelines and felt our way across to Moto Hill and back. 

Important stuff first. As we approached our second pit site on the lip of Moto Hill (southeast aspect at 8600'), I stopped and looked back in time to see avalanche debris slamming into the trees on a connected slope below. We remotely triggered the avalanche from 150 feet away. It broke 200' wide and 1-3 feet deep. It ran an estimated 200' vertical feet (based on a slope map. We couldn't safely access the toe of the debris). The avalanche failed on a layer of Fist hard facets. This is interesting because it is these mid-elevation slopes in the LH area that seemed really weak on previous visits to the area. The slope may have some wind-loading, but it was minimal and not the cause of this avalanche. 

We dug a pit on an east aspect around the corner and down from Airplane Bowl (before the avalanche) and found a similar snowpack setup. 150 cm of total snow and half was composed of weak facets. ECTP22 and P24 on the mid-pack January layer of Fist hard facets and surface hoar

Take Homes: 

  1. Lionhead seems to be the epicenter of persistent slab instability. It is the weakest I have seen. Southern Madison and Southern Gallatin seem to be similar and I would group them together when describing conditions. 
  2. Mid-elevation slopes are thin and weak and can clearly avalanche. This is problematic because many folks play in lower elevation terrain when conditions are dangerous... While small compared to the upper bowl, the avalanche we triggered would have been deadly. It was deep and it would have strained its victim through trees. 
  3. We heard about a similar remote-triggered avalanche in Black Canyon today. This has me nervous that I missed something in the Centennials. While we didn't see anything too concerning there yesterday outside of wind-loaded slope, I am not happy about two remotely triggered slides less than 20 mile away. 
Region
Lionhead Range
Location (from list)
Lionhead Ridge
Observer Name
Zinn and Staples

Remotely Triggered Avalanche in Black Canyon

Black Canyon
Out of Advisory Area
Code
SS-AMr-R3-D2-O
Elevation
8000
Latitude
44.47800
Longitude
-111.13500
Notes

From SnoWest Forums FB Page:

“Just getting word of a LARGE Remote Rider Triggered Slab Avalanche down inside of Black Canyon itself just off the Black Canyon Loop Trail in Island Park.
A 3-4ft thick slab broke loose and filled the bottom of the canyon with 12-15 FEET of debris, completely blocking off the canyon itself. Rider was NOT caught in it!! Had the rider been caught, there would have been ZERO chance of rescue under such a deep slide!”

Number of slides
1
Number caught
0
Number buried
0
Avalanche Type
Soft slab avalanche
Trigger
Snowmobile
Trigger Modifier
r-A remote avalanche released by the indicated trigger
R size
3
D size
2
Bed Surface
O - Old snow
Problem Type
Deep Persistent Slab
Slab Thickness
36.0 inches
Slab Thickness units
inches
Single / Multiple / Red Flag
Single Avalanche
Advisory Year

From SnoWest Forums FB Page:

“Just getting word of a LARGE Remote Rider Triggered Slab Avalanche down inside of Black Canyon itself just off the Black Canyon Loop Trail in Island Park.
A 3-4ft thick slab broke loose and filled the bottom of the canyon with 12-15 FEET of debris, completely blocking off the canyon itself. Rider was NOT caught in it!! Had the rider been caught, there would have been ZERO chance of rescue under such a deep slide!”

Out of Advisory Area, 2025-02-19

Remotely Triggered Avalanche in Black Canyon

Date
Activity
Snowmobiling

From SnoWest Forums FB Page:

“Just getting word of a LARGE Remote Rider Triggered Slab Avalanche down inside of Black Canyon itself just off the Black Canyon Loop Trail in Island Park.
A 3-4ft thick slab broke loose and filled the bottom of the canyon with 12-15 FEET of debris, completely blocking off the canyon itself. Rider was NOT caught in it!! Had the rider been caught, there would have been ZERO chance of rescue under such a deep slide!”

Region
Out of Advisory Area
Location (from list)
Black Canyon
Observer Name
SnoWest Forums Facebook

Avalanche on Saddle Peak, Bridgers

Date
Activity
Skiing

No wind today, but recent loading 

Note from BB ski patrol - skiers triggered a medium sized cornice fall that triggered a dry loose (sluff) avalanche that created large powder cloud.

Region
Bridger Range
Location (from list)
Saddle Peak
Observer Name
Steve White

Cold powder and little else of note

Date
Activity
Skiing

Skied up the southern of the two typical Bacon Rind skintracks (through the more heavily burned area to the upper meadows). Saw no signs of instability (no cracking, collapsing, or recent avalanches).

Dug a pit on an E aspect at 8800 ft in one of the upper meadows. 128 cm snow depth. No propagation in an Extended Column Test. There is weak snow at the ground, but it isn't super well developed or very weak (4 Finger minus hardness).

No wind affect where we traveled today. 

Region
Southern Madison
Location (from list)
Bacon Rind
Observer Name
Ian Hoyer