23-24

Windslab avalanche in bear basin

Date
Activity
Skiing

Went up to the prayer flags today. On the ridge about 100yards below the flags I went to the end of the cornice and gave it a stomp. Triggered a windslab that propagated about 50 to the left. 
HS-ASc- D1-R1-I

The crown was roughly 1-1.5 ft deep in the most wind loaded area. 
Multiple slides have went on this slope already this year, some running a good distance down through the trees. 

Region
Northern Madison
Location (from list)
Bear Basin
Observer Name
Jay Alford

More wind, and poor snowpack structure

Date
Activity
Snowmobiling

We rode up the road to Henderson Bench and dug on a northeast facing slope at 9,670'. While digging it was clear how poor the snowpack structure was. It was difficult to dig through a 2 foot thick hard slab, but once through the slab I sunk to the ground through 1.5 feet of weak sugary facets. We had an ECTX. After some extra hits, removing 2/3 of the slab, and a few more hard hits, we got a dramatic collapse and propagation. The facets were F+ in hardness below a P+ hard slab. Although the weak layer was difficult to affect in this spot, finding the right spot on a slope to collapse the weak layer would produce a big avalanche, as shown by a rider triggered slide two days ago on Fisher Mtn.

We also rode up to Daisy Pass. Visibility was good enough to see most slopes, but in flat light. We didn't notice any new avalanches.

Snow was falling lightly (S -1). Overcast skies. Wind was moderate with frequent strong gusts out of the west-southwest, forming drifts along road cuts and convexities.

 

Region
Cooke City
Location (from list)
Henderson Bench
Observer Name
Alex Marienthal

GNFAC Avalanche Forecast for Sun Feb 25, 2024

Snowpack and Avalanche Discussion

<p><span><span><span><span><span><span>Strong winds have been blowing snow into thick drifts over an already unstable snowpack. Human-triggered avalanches are likely and natural avalanches are possible, especially on wind-loaded slopes. On Friday, a rider near Cooke City triggered a large avalanche, was caught and luckily not buried or injured (</span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/30998"><span><span><span><strong><span… City photos</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span>), and a pair near Big Sky triggered two large avalanches from flat terrain nearby (</span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/30994"><span><span><span><strong><span…;). Yesterday north of Cooke City, wind was actively forming thick drifts (</span></span></span></span></span></span><a href="https://www.youtube.com/watch?v=dmhwDbpONLM&amp;list=PLXu5151nmAvSH326z…;), and we saw a recent avalanche that appeared natural or rider triggered in the previous 24 hours (</span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/31016"><span><span><span><strong><span…;).</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>Recent avalanches show an unstable snowpack exists and will not improve with wind-loading today (and heavy snow tomorrow). We have seen steady avalanche activity since early January, even during times without new snow or wind (</span></span></span></span></span></span><a href="https://www.mtavalanche.com/weather/wx-avalanche-log"><span><span><span… and avalanche log</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span>). Weak layers buried 2-4 feet deep make up the foundation of the snowpack, and are as weak as we’ve seen. People can trigger large avalanches, potentially from flatter terrain below steep slopes. The best plan is to avoid riding on or below slopes steeper than 30 degrees. Avalanche danger is CONSIDERABLE.</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>In the Bridger Range and northern Gallatin Range you can trigger a large avalanche that breaks 1-3 feet deep on weak sugary snow, and freshly wind-loaded slopes should be avoided. Although less snow over the last week means recent wind-loading is relatively minimal compared to the rest of the area, we can’t trust this season’s very weak snowpack with even the smallest addition of weight. Avalanches last weekend near </span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/30935"><span><span><span><strong><span… Peak</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/30937"><span><span><span><strong><span… of Saddle Peak</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span> in the Bridger Range, and on </span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/30949"><span><span><span><strong><span…. Bole</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span> in Hyalite are examples of the avalanche potential.</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>On non-wind-loaded slopes the likelihood of a slide is lower, but consequences are similar. Before traveling in avalanche terrain carefully assess the snowpack and identify areas to avoid. Choose smaller, simple slopes with clean runouts and no wind-loading. Avoid wind-loaded slopes, and complex terrain with terrain traps such as cliffs, trees or confined gullies. As a final check before committing to steep slopes, do a quick stability test. Look for signs of instability and be ready to change plans if you see any red flags. Avalanche danger is CONSIDERABLE on wind-loaded slopes and MODERATE on non-wind-loaded slopes in the mountains near Bozeman.</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>Watch </span></span></span></span></span></span><a href="https://www.youtube.com/watch?v=vD42TrROj7k&amp;list=PLXu5151nmAvSH326z…’s video from the Throne</span></span></u></span></strong></span></span></span></a><span><span><span><strong><span><span> </span></span></strong></span></span></span><span><span><span><span><span><span>and </span></span></span></span></span></span><a href="https://www.youtube.com/watch?v=On68EbgLFbM&amp;list=PLXu5151nmAvSH326z…’s video from Hyalite</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span> for more travel and snowpack assessment tips during these conditions.</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.

Recent Avalanche on Sheep Mtn., Cooke

Sheep Mountain
Cooke City
Code
HS-R3-D2-O
Elevation
10000
Aspect
N
Latitude
45.07850
Longitude
-109.93700
Notes

On 2/24/24 We saw a slide on the north end of Sheep Mtn. on a slope above the steep chute where people climb out of Goose Creek (photos attached). This slide had not been reported previously and looked similar in age to the two triggered yesterday, so maybe broke naturally or human-triggered in last 24 hours. It broke near a scoured north facing ridgeline, 1-1.5' deep, 175' wide. HS-R3-D2-O.

Number of slides
1
Number caught
0
Number buried
0
Avalanche Type
Hard slab avalanche
R size
3
D size
2
Bed Surface
O - Old snow
Problem Type
Persistent Weak Layer
Slab Thickness
14.0 inches
Vertical Fall
500ft
Slab Width
175.00ft
Slab Thickness units
inches
Single / Multiple / Red Flag
Single Avalanche
Advisory Year

On 2/24/24: We saw a slide on the north end of Sheep Mtn. on a slope above the steep chute where people climb out of Goose Creek. This slide had not been reported previously and looked similar in age to the two triggered yesterday, so maybe broke naturally or human-triggered in last 24 hours. It broke near a scoured north facing ridgeline, 1-1.5' deep, 175' wide. HS-R3-D2-O. Photo: GNFAC

Cooke City, 2024-02-25

On 2/24/24: We saw a slide on the north end of Sheep Mtn. on a slope above the steep chute where people climb out of Goose Creek. This slide had not been reported previously and looked similar in age to the two triggered yesterday, so maybe broke naturally or human-triggered in last 24 hours. It broke near a scoured north facing ridgeline, 1-1.5' deep, 175' wide. HS-R3-D2-O. Photo: GNFAC

Cooke City, 2024-02-25

On 2/24/24: We saw another slide on the north end of Sheep Mtn. on a slope above the steep chute where people climb out of Goose Creek. This slide had not been reported previously and looked similar in age to the two triggered yesterday, so maybe broke naturally or human-triggered in last 24 hours. It broke near a scoured north facing ridgeline, 1-1.5' deep, 175' wide. HS-R3-D2-O. Photo: GNFAC

 

Cooke City, 2024-02-25

On 2/24/23 we got a pretty good look at the slides on Fisher Mtn. that were triggered yesterday. They appeared 2-3 feet deep, and the debris was very hard. Crowns were already at least half drifted in. Photo: GNFAC

Cooke City, 2024-02-25