23-24

Another big avalanche, on Sheep Mtn.

Date
Activity
Snowmobiling

We rode to Round Lake and around the north and west side of Sheep, and back out through Round Lake. There was a big avalanche on the northeast side of Sheep that was previously not reported. It was there this morning so maybe happened yesterday. 6-8'+ deep, 500' wide R4-D3-O.

This morning we saw previous avalanches on Henderson Mtn. in better light and got a photo of one on the lower Henderson Bench. Showing wide propagation through thick trees.

Temps were warm under clear skies with calm wind. Snow surface was getting moist in the afternoon on sunny slopes.

Region
Cooke City
Location (from list)
Sheep Mountain
Observer Name
Alex Marienthal

GNFAC Avalanche Forecast for Sat Mar 9, 2024

Snowpack and Avalanche Discussion

<p><span><span><span><span><span><span>Dangerous avalanche conditions exist and large human triggered avalanches are likely.&nbsp; Snowfall earlier this week pushed the snowpack past its breaking point. Alex rode around the motorized zone yesterday and reported that it was “maybe the most widespread large activity I have ever seen” (</span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/31331"><span><span><span><strong><span…;).&nbsp;</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>Thursday’s snowmobile triggered slide on Henderson Mountain was even bigger than we initially reported, breaking over 2000 ft wide and all the way up to the ridgeline, generally 6-10 ft deep and 12-15 ft deep in the deepest section (</span></span></span></span></span></span><a href="https://www.youtube.com/watch?v=7F4hYSm-iEY"><span><span><span><strong>… video</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span>). Two more very large slides were likely triggered by snowmobiles yesterday on different faces of Scotch Bonnet Mountain (</span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/31345"><span><span><span><strong><span…;, </span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/31357"><span><span><span><strong><span…;, </span></span></span></span></span></span><a href="https://www.youtube.com/watch?v=9kyGpQxAs2A"><span><span><span><strong>… Bonnet video</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span>). We expect more of the same today. Avoid riding on any slope steeper than 30 degrees and give them a wide berth as you pass beneath them as well.</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>The avalanche danger is rated CONSIDERABLE.&nbsp;</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>Triggering large avalanches is a very real and dangerous possibility today. The likelihood of triggering slides has marginally decreased over the last couple days without snowfall, but the potential size and consequences of triggering a slide have not. Close calls in Beehive Basin and on Saddle Peak yesterday drive home the seriousness of conditions right now.&nbsp;</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>Yesterday, skiers in Beehive Basin triggered an avalanche that broke 500 ft wide and up to 6 ft deep by dropping a section of cornice onto a slope (</span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/31343"><span><span><span><strong><span… and photos</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span>). </span></span></span></span></span></span><span><span><span><span><em><span>This slide took out the skin track up the face they had just broken on the ascent. </span></em></span></span></span></span><span><span><span><span><span><span>Slides breaking on these deeper weak layers are likely to be unsurvivable, regardless of any terrain considerations.&nbsp;</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>Somewhat smaller avalanches breaking in wind drifted snow could also have devastating consequences in the wrong spot. Two skiers, at different times yesterday, triggered avalanches on Saddle Peak (</span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/31330"><span><span><span><strong><span… and photos</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span>). The larger slide initially broke about a foot deep, but then triggered a secondary slab that broke 1-3 ft deep and 200 ft wide before running over the large main cliff band. Thankfully the skier was not caught and did not take this unsurvivable ride and no one happened to be beneath the cliffs as the debris came down from above.</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>If you are considering stepping out into steeper terrain, our recommendation is to ease into lower-consequence terrain and religiously follow safe travel protocols in case something goes wrong. </span></span></span></span></span></span><span><span><span><strong><span><span>To be crystal clear, skiing on Saddle Peak is the antithesis of these recommendations with large, steep slopes, and big cliffs, and other groups likely to be both above and below you.</span></span></strong></span></span></span></p>

<p><span><span><span><span><span><span>The avalanche danger is rated MODERATE today.</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.

Older avalanche on Ross E shoulder

Date

Saw a large slide (D2.5, R3 or 4) on Ross East shoulder that likely occurred in the March 3/4 timeframe. 3 to 4 feet deep crown in places. Looked around at the bed surface which was nearly to the rock slabs underneath.

Natural Avalanches on Henderson Bench

Henderson Bench
Cooke City
Code
N
Aspect
E
Latitude
45.05580
Longitude
-109.94700
Notes

On 03/08/2024 we saw widespread avalanches along Henderson Bench as well, below the steep break over in the trees, 3'+ deep breaking across multiple terrain features through thick trees, most of the bench slid, and appeared to have happened last weekend.

Number caught
0
Number buried
0
Trigger
Natural trigger
Problem Type
Persistent Weak Layer
Slab Thickness
36.0 inches
Snow Observation Source
Slab Thickness units
inches
Single / Multiple / Red Flag
Multiple Avalanches
Advisory Year

Natural Avalanche on Barronette

COOKE CITY
Cooke City
Code
N
Latitude
45.02020
Longitude
-109.93800
Notes

From 03/08/2024: On my drive to Cooke City I saw old slab avalanches in YNP near Mammoth and on Abiathar and Ampitheater among other places. These appeared to have happened earlier in the week. I also saw a more fresh looking persistent slab avalanche on Barronette, 2-3' deep and as wide as its terrain feature, 100-200' (photo).

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

On my drive to Cooke City I saw old slab avalanches in YNP near Mammoth and on Abiathar and Ampitheater among other places. These appeared to have happened earlier in the week. I also saw a more fresh looking persistent slab avalanche on Barronette, 2-3' deep and as wide as its terrain feature, 100-200' Photo: GNFAC

Cooke City, 2024-03-08

Avalanche north side of Scotch Bonnet

Scotch Bonnet
Cooke City
Code
R1-D1.5-O
Aspect
N
Latitude
45.07330
Longitude
-109.94800
Notes

We saw one small but deep slab on the north side of Scotch Bonnet, 6' deep x 30' wide, R1-D1.5.

 

Number of slides
1
Number caught
0
Number buried
0
R size
1
D size
1.5
Bed Surface
O - Old snow
Problem Type
Persistent Weak Layer
Slab Thickness
72.0 inches
Slab Width
30.00ft
Snow Observation Source
Slab Thickness units
inches
Single / Multiple / Red Flag
Single Avalanche
Advisory Year

Avalanche South side of Scotch Bonnet

Scotch Bonnet
Cooke City
Code
HS-R4-D3-O
Aspect
S
Latitude
45.07330
Longitude
-109.94800
Notes

We saw a fresh huge avalanche on the south side of Scotch Bonnet that happened today, 03/08, or late yesterday. 4-6' deep and 300' wide. R4-D3-O. 

 

Number of slides
1
Number caught
0
Number buried
0
Avalanche Type
Hard slab avalanche
R size
4
D size
3
Bed Surface
O - Old snow
Problem Type
Persistent Weak Layer
Slab Thickness
60.0 inches
Slab Width
300.00ft
Snow Observation Source
Slab Thickness units
inches
Single / Multiple / Red Flag
Single Avalanche
Advisory Year