23-24

Avalanche accident on Twin Peaks

Flint Creek Range
Butte Area
Code
AMu-R3-D2.5-O
Latitude
46.32370
Longitude
-113.10200
Notes

2 Snowmobilers riding into the Twin Peaks area, and one decided to sidehill a slope with patchy larch trees that is 42 degrees at the top, and consistently windloaded.  The resulting avalanche took him and his sled approximately 300 feet downhill to a patch of small diameter larch trees where the trees formed a fence that strained the rider and his sled and also piled up the debris.  It was likely one of these small trees that broke the victim's leg.  They were very familiar with the area, and all the previous accidents (one fatality occurred north of this spot by 150 yds, and several full and partial burials have occurred along this ridge) that have happened in that area.  They were carrying all rescue gear and airbags(victim did not deploy his airbag).  One of the riders was at an avalanche class I put on at the toe of the slope 5 years ago.  There was no real hazard evaluation, and the riders did not observe any signs of instability prior to triggering the avalanche. Once the rider sidehilled into the open everything fractured above him in the windslab.  My partner and I had several large collapses assessing the area, and the victim's riding partner stated that they had several collapses moving the victim to the helicopter.  The helicopter landed very close to the toe of the slope.  The snow depth at the crown was 60 inches deep, with one wind slab sitting on another on facets, and at the toe of the slope the snow depth was less than 20 inches deep.  The fracture traveled roughly 800 feet in and around the larch trees near the top of the slope and it deposited debris in 3 different run outs.

Victim was buried vertically with a boot sticking out, and his riding partner exposed his face in 2 minutes.  He extricated his whole body in 8-10.  He had a broken femur and a broken hand.  As they were digging, rescuers stated that the second leg wasn't vertical, and they found it at an oblique angle to the rest of the body.  They had an inreach and sent out a help signal that was picked up, and LifeFlight was nearby.  Lifeflight was able to land at the base of the slope and take him to St. Pete's in Missoula at 1230 pm.

Photo: https://www.mtavalanche.com/images/24/twin-peaks-avalanche

Number of slides
1
Number caught
0
Number buried
0
Trigger
Snowmobile
Trigger Modifier
u-An unintentional release
R size
3
D size
2.5
Bed Surface
O - Old snow
Slab Thickness
60.0 inches
Slab Width
800.00ft
Slab Thickness units
inches
Single / Multiple / Red Flag
Single Avalanche
Advisory Year

GNFAC Avalanche Forecast for Thu Jan 25, 2024

Snowpack and Avalanche Discussion

<p><span><span><span><span><span><span>We issued an Avalanche Warning for the third day in a row in Island Park because it keeps snowing. An inch or two of new snow is keeping the snowpack very dangerous. Since Saturday, 1.5” of snow water equivalent fell, measuring a foot and a half of snow. Avalanches can be triggered from hundreds of feet away and getting caught could be deadly. Our advice is simple: don’t get into or underneath any avalanche terrain. The avalanche danger is rated HIGH on all slopes. </span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>A large avalanche on Henderson Mountain in Cooke City was seen yesterday (</span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/30222"><span><span><span><strong><span… and photos</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span>). It likely occurred the night before or yesterday morning and we are unsure of the trigger. No matter. This avalanche illustrates why we are worried: the snowpack is on edge, it is slow to adjust to even the smallest amount of snow, and remains very unstable for a long period of time. Read </span></span></span></span></span></span><span><span><span><span><em><u><span><span>The Last Word</span></span></u></em></span></span></span></span><span><span><span><span><span><span> at the end of the advisory for an explanation on these unusual conditions.&nbsp;</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>On Sunday, Alex and Dave triggered a slide at Lionhead (</span></span></span></span></span></span><a href="https://www.youtube.com/watch?v=mSked07bAY8&amp;lc=UgwOJBQp1Ujv-9h17St4…;) and a similar avalanche could occur today. Slopes that have added weight from previous wind-loading are extra susceptible to avalanching, just like the slide on Henderson Mountain. Last night, we were sent </span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/30233"><span><span><span><strong><span… photos</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span> of recent slides in Cooke City, even more evidence of the snowpack’s danger.&nbsp; I recommend staying off slopes steeper than 30 degrees and being extra careful traveling under slopes.&nbsp;</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>The avalanche danger is HIGH on previously wind-loaded slopes and CONSIDERABLE on all others.</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>The snowpack in the Bridger, Madison and Gallatin Ranges remains weak and unstable. Even days after a storm the danger remains elevated. An unusually weak snowpack is creating unusual avalanche conditions. Slopes can be triggered from far away as Dave discovered on Buck Ridge on Sunday (</span></span></span></span></span></span><a href="https://youtu.be/jDOAJ1yGmGk"><span><span><span><strong><span><u><span>…;) and others on </span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/30123"><span><span><span><strong><span… Mountain</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span> and </span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/30129"><span><span><span><strong><span… Peak</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span>. And let’s not forget </span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/30161"><span><span><span><strong><span… Peak</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span>, where a skier triggered a large avalanche far below the ridge. Dave and I turned around on the </span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/13952"><span><span><span><span><span><…; in the northern Bridger Range because we were worried about triggering a slide far above us (</span></span></span></span></span></span><a href="https://youtube.com/shorts/ZaeaIBk64uM?feature=share"><span><span><span…;). The backcountry is dangerous and will remain so for a while. Karl Birkeland, avalanche scientist, wrote, “This snowpack is gonna take a LONG time to stabilize every time it gets loaded. Have patience. This snowpack is unlikely to get completely better until it's melted and heading down the rivers in the spring!” Not exactly what I wanted to hear, but likely true nonetheless. Read </span></span></span></span></span></span><span><span><span><span><em><u><span><span>The Last Word</span></span></u></em></span></span></span></span><span><span><span><span><span><span> at the end of the advisory for an explanation on these unusual conditions.&nbsp;</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>If you go into avalanche terrain it’s likely you’ll trigger a slide today. Consequently, the avalanche danger is rated CONSIDERABLE.</span></span></span></span></span></span></p>

Upcoming Avalanche Education and Events

Our education calendar is full of awareness lectures and field courses. Check it out: Events and Education Calendar.

Natural Avalanches in Cooke City

COOKE CITY
Cooke City
Code
Latitude
45.02020
Longitude
-109.93800
Notes
Photos from today (1/24/24).  A couple of these slides look to be fresh in the last 48 hrs.

Also that large avalanche observed today on the SE aspect Mt. Henderson was not visible there at 4pm yesterday (1/23)

Number of slides
4
Number caught
0
Number buried
0
Snow Observation Source
Slab Thickness units
centimeters
Single / Multiple / Red Flag
Multiple Avalanches
Advisory Year

Natural Avalanches in Cooke City

Date
Activity
Skiing
Photos from today (1/24/24).  A couple of these slides look to be fresh in the last 48 hrs.

Also that large avalanche observed today on the SE aspect Mt. Henderson was not visible there at 4pm yesterday (1/23)

Region
Cooke City
Location (from list)
COOKE CITY
Observer Name
Beau Fredlund

Blackmore

Date
Activity
Skiing

Dug on an E (105deg) slope at 9600 feet on Mt. Blackmore. This was a quick pit not a full profile.

SKY: SCT Wind: L variable 

HS 95cm

ECTN15 down 40cm on 1-2mm facets.

Snow above facets was mostly 4F to 4F+. While there was no propagation observed in the pit, the structure was quite poor. Additional stiffening of the slab and/or loading in the future could likely easily increase the propagation propensity. 

approx. 3-4+mm facets down 60cm were also worth noting.

Recent wind effect was evident on lee slopes. 

We had predetermined that avalanche terrain was "closed" for the day as we were just out collecting info/obs and skied low angle slopes and the rather spicy re-frozen skin track out.

 

 

Region
Northern Gallatin
Location (from list)
Mt Blackmore

Blue X marks the location of a snowmobiler who was buried by an avalanche on Jan. 20th. The victim was uncovered and transported to medical care. 

From Obs: "The snow depth at the crown was 60 inches deep, with one wind slab sitting on another on facets, and at the toe of the slope the snow depth was less than 20 inches deep.  The fracture traveled roughly 800 feet in and around the larch trees near the top of the slope and it deposited debris in 3 different run outs."

 

Butte Area, 2024-01-24