23-24

Avalanche on Henderson Mountain

Henderson Bench
Cooke City
Code
SS-R3-D2
Aspect
S
Latitude
45.05580
Longitude
-109.94700
Notes

From obs: "Was out today and noticed this large avalanche on the south side of Henderson. Looks like it happened today or yesterday. Possible remote trigger, snowmobilers were riding underneath that zone. The slide looks about 200 feet across and 4 feet deep in the thickest spot. D2. "

 

Number of slides
1
Number caught
0
Number buried
0
Avalanche Type
Soft slab avalanche
R size
3
D size
2
Problem Type
Persistent Weak Layer
Slab Thickness
24.0 inches
Slab Width
199.99ft
Snow Observation Source
Slab Thickness units
inches
Single / Multiple / Red Flag
Single Avalanche
Advisory Year

Natural Avalanche in Tepee Basin

Tepee Basin
Southern Madison
Code
Elevation
8500
Aspect
NE
Latitude
44.90410
Longitude
-111.18500
Notes

We saw a natural avalanche above the first meadow of Tepee. This avalanche is old and likely happened a few days ago near the end of the last storm on 01/20. NE facing slope at ~8500 feet. 

 

Number of slides
1
Number caught
0
Number buried
0
Snow Observation Source
Slab Thickness units
centimeters
Single / Multiple / Red Flag
Single Avalanche
Advisory Year

Old Natural Avalanche in Tepee Basin

Date
Activity
Snowmobiling

We rode into Tepee Basin today to practice rescue skills with snow rangers from different districts across the Custer-Gallatin Forest. On top of a great day riding and practicing rescue skills we saw a natural avalanche above the first meadow of Tepee. This avalanche is old and likely happened a few days ago near the end of the last storm on 01/20. NE facing slope at ~8500 feet. 

There is plenty of snow on the ground to practice rescue. Now is as good of a time as any to get out and practice your skills! 

Region
Southern Madison
Location (from list)
Tepee Basin
Observer Name
Zach Peterson

Avalanche accident on Twin Peaks

Date
Activity
Snowmobiling

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.

Region
Butte Area
Location (from list)
Flint Creek Range
Observer Name
Will Shoutis

Avalanche on Mt Henderson

Date
Activity
Skiing
Snowmobiling

 Was out today and noticed this large avalanche on the south side of Henderson. Looks like it happened today (1/24) or yesterday (1/23). Possible remote trigger, there were snowmobilers riding underneath that zone. The slide looks about 200 feet across and 4 feet deep in the thickest spot. D2. 

Dug a pit over there. HS 145. ECTP19 50 cm down on surface hoar. 

From B. Fredlund: "...large avalanche observed today on the SE aspect Mt. Henderson was not visable there at 4pm yesterday." (1/23).

Region
Cooke City
Location (from list)
Henderson Bench
Observer Name
Jake Mundt

GNFAC Avalanche Forecast for Wed Jan 24, 2024

Snowpack and Avalanche Discussion

<p><span><span><span><span><span><span>We issued an Avalanche Warning for the second day in a row in Island Park because it keeps snowing. Although the daily amounts are measured in inches, they add up. Since Saturday, 1.4” of snow water equivalent fell, measuring over a foot of snow. Avalanches will be easily triggered and getting caught could be deadly, especially if you are trapped in a gully with snow piling on top of you. Our advice is simple: don’t get into or underneath any avalanche terrain today. Avalanches can be triggered from hundreds of feet away. The avalanche danger is rated HIGH on all slopes. </span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>In the southern mountains, slopes that have more snow (more weight) are the most worrisome. We find this on slopes that were previously wind-loaded. </span></span></span></span></span></span><span><span><span><span><em><span>Typically, wind-loads stabilize quickly, but the snowpack is not typical, it is wickedly fragile.</span></em></span></span></span></span><span><span><span><span><span><span> Even though the wind has been calm, wind drifts formed over the weekend should not be touched and can be found at ridgelines and in gullies.&nbsp;</span></span></span></span></span></span></p>

<p><span><span><span><span><em><span>Incremental loading, an inch or two every day, is also not typically a problem, except this year.</span></em></span></span></span></span><span><span><span><span><span><span> Collapsing, cracking and triggering slides from far away is as likely today as it was yesterday. Take a peek at the </span></span></span></span></span></span><a href="https://www.mtavalanche.com/avalanche-activity"><span><span><span><stro… activity log</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span> to see how a small amount of snow can produce avalanches. On Sunday, Dave and Alex 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 similar avalanches could occur today. Reports of folks tip-toeing around Cooke City amongst a sea of collapses and cracks makes my palms sweat.&nbsp;</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>The bottom 2 feet of the snowpack is garbage: sugary facets and a couple layers of surface hoar. I recommend staying off slopes steeper than 30 degrees and be extra careful traveling under slopes. 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>Yesterday, Dave and I went into 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. The conditions we found were expected and also similar to the northern mountain ranges: weak and unstable. We did not need to do a stability test because the collapses were numerous and loud and indicated that we could trigger a slide from hundreds of feet away (aka remote trigger).&nbsp; In the last few days, skiers remotely triggered </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>,&nbsp; </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 Dave remotely triggered a slide from 750 feet away (</span></span></span></span></span></span><a href="https://youtu.be/jDOAJ1yGmGk"><span><span><span><strong><span><u><span>…;) on his snowmobile at Buck Ridge. Not far from the Throne, a lone skier triggered a large avalanche on Saddle Peak on Sunday (</span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/30161"><span><span><span><strong><span… and photos</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span>). Collapsing, cracking, a small slide on the Throne triggered Sunday by a few wet snowballs, and nervousness about triggering the slope above us made our decision to retreat an easy one (</span></span></span></span></span></span><a href="https://youtube.com/shorts/ZaeaIBk64uM?feature=share"><span><span><span…;). Further south in Beehive Basin, students in an avalanche class were able to take advantage of the unstable conditions and intentionally triggered a small test slope (</span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/30216"><span><span><span><strong><span… and pics</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span>).&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

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