20-21

This 4' deep snowpit shows the new snow over the last 4 days: everything above the blue card, over 2' of snow measuring 2" of SWE. Avalanches are breaking on the very weak, sugary snow (facets and depth hoar) 1-1.5 feet above the ground. The smooth surface in the bottom left of the photo is the failure plane. Photo: GNFAC

Bridger Range, 2021-02-07

Small natural slide on Saddle Peak

Saddle Peak
Bridger Range
Code
SS-N-R1-D1.5
Elevation
8900
Aspect
NE
Latitude
45.79430
Longitude
-110.93600
Notes

Bridger Bowl ski patrol noted natural avalanche debris below the cliffs of Saddle Peak. It appeared to involve only the new snow, but started high on the face and ran over the cliffs with a decent debris pile below going home chute.

Number of slides
1
Number caught
0
Number buried
0
Avalanche Type
Soft slab avalanche
Trigger
Natural trigger
R size
1
D size
1.5
Problem Type
New Snow
Slab Thickness units
centimeters
Single / Multiple / Red Flag
Single Avalanche
Advisory Year

Skier triggered slide from cornice, Cooke

Hayden Creek
Cooke City
Code
U-AS
Elevation
9800
Aspect
E
Latitude
44.99520
Longitude
-109.90800
Notes

From a skier: "as we were digging a pit, we got into a conversation with three skiers as they skinned past. They had skinned up Rip Curl (from Hayden Creek) and then continued S. along Woody Ridge. They experienced several large collapses along the ridge line and eventually remotely triggered a cornice collapse that set off an avalanche (described as a large powder cloud) in the Climax slide path (E. aspect)."

 

Number of slides
1
Number caught
0
Number buried
0
Avalanche Type
Unknown
Trigger
Skier
Problem Type
New Snow
Slab Thickness units
centimeters
Single / Multiple / Red Flag
Single Avalanche
Advisory Year

GNFAC Avalanche Forecast for Sun Feb 7, 2021

Snowpack and Avalanche Discussion

<p>Over the last couple days there have been reports of large natural avalanches, collapsing and cracking in the Bridger Range (<strong><a href="https://www.mtavalanche.com/node/24102">Saddle Peak and Truman</a></strong>, <strong><a href="https://www.mtavalanche.com/node/24112">N. Bridgers</a></strong>), <a href="https://www.mtavalanche.com/node/24098">Hyalite</a&gt;, and the <a href="https://www.mtavalanche.com/node/24100">southern Gallatin Range</a>. Many of which broke wide on sugary, buried weak layers. Since Wednesday the mountains near Bozeman and Big Sky, and the southern Madison and Gallatin ranges received 2-4 feet of snow equal to 2-3.5” of snow water equivalent (SWE). Strong west-northwest winds over the last 48 hours drifted this snow into thick slabs that can avalanche naturally or easily be triggered by skiers or riders. Today, with continued snow and wind, very dangerous avalanche conditions exist and danger is HIGH on all slopes. Avoid travel on and underneath steep slopes.</p>

<p>Since Wednesday the mountains near Cooke City received over three feet of snow equal to 2.6” of &nbsp;snow water equivalent. On Friday&nbsp;a skier triggered and was partially buried in an avalanche south of town (<strong><a href="https://www.mtavalanche.com/node/24075">photo and details</a></strong>). Moderate to strong westerly wind the last couple days, with more snow and wind today make natural and human triggered avalanches likely. I was in Cooke City the last few days where avalanches breaking in the new snow were a growing concern, especially where new snow has been drifted into thicker slabs (<strong><a href="https://www.youtube.com/watch?v=u1BY8bb327k&amp;list=PLXu5151nmAvQDzKmH…;). Avalanches of recent snow will be large enough to bury a person, and some slopes could break deeper on buried weak layers. Today the avalanche danger is HIGH on all slopes. Avoid travel on and underneath steep slopes.</p>

<p>Yesterday near Lionhead Ridge a snowmobiler triggered an avalanche that broke wide, and luckily nobody was caught (<strong><a href="https://www.mtavalanche.com/node/24111">photo</a></strong&gt;). Since Wednesday the mountains near West Yellowstone received 2 feet of snow equal to 2.1” SWE, with an inch or two possible today. A layer of weak, sugary snow buried 3-4 feet deep can collapse under the weight of a person, and break wide across slopes (<a href="https://youtu.be/CI0HFvtLrf4"><strong>Lionhead video</strong></a>). Today human triggered avalanches are likely and natural avalanches are possible, especially on wind loaded slopes. Avalanche danger is CONSIDERABLE. Very careful route finding is essential.</p>

<p>If you get out, please send us your observations no matter how brief. You can submit them via our <a href="https://www.mtavalanche.com/node/add/snow_observation"><strong>website<…;, email (<a href="mailto:mtavalanche@gmail.com"><strong>mtavalanche@gmail.com</strong></a…;), phone (406-587-6984), or Instagram (#gnfacobs).</p>

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Skier remote triggered small slab, N. Bridgers

BRIDGER RANGE
Bridger Range
Code
SS-ASr-R3-D1.5-G
Latitude
45.85120
Longitude
-110.94800
Notes

Skiers sent an IG post saying they remote triggered this slide from the adjacent road on 2/6/21.

Number of slides
1
Number caught
0
Number buried
0
Avalanche Type
Soft slab avalanche
Trigger
Skier
Trigger Modifier
r-A remote avalanche released by the indicated trigger
R size
3
D size
1.5
Bed Surface
G - Ground
Problem Type
New Snow
Slab Thickness
12.0 inches
Vertical Fall
20ft
Slab Width
40.00ft
Slab Thickness units
inches
Single / Multiple / Red Flag
Single Avalanche
Advisory Year

Snowmobile triggered near Lionhead

LIONHEAD AREA
Lionhead Range
Code
SS-AMu-R3-D2-I
Elevation
8000
Aspect
S
Latitude
44.72920
Longitude
-111.32300
Notes

Riders wrote that they triggerend an avalanche on a south facing slope in West Targhee Creek on 2/6/21. No one was caught.

Number of slides
1
Number caught
0
Number buried
0
Avalanche Type
Soft slab avalanche
Trigger
Snowmobile
Trigger Modifier
u-An unintentional release
R size
3
D size
2
Bed Surface
I - Interface between new and old snow
Problem Type
New Snow
Slab Thickness
24.0 inches
Vertical Fall
200ft
Slab Width
300.00ft
Slab Thickness units
inches
Single / Multiple / Red Flag
Single Avalanche
Advisory Year

Small Natural Avalanches north of Bridger

Wolverine Bowl
Bridger Range
Code
N-R1-D1.5
Elevation
7900
Aspect Range
E, NE
Latitude
45.83010
Longitude
-110.93400
Notes

Signs of a small natural avalanche on lower wolverine bowl and north Bradley's.

Number of slides
2
Number caught
0
Number buried
0
Trigger
Natural trigger
R size
1
D size
1.5
Problem Type
New Snow
Slab Thickness units
centimeters
Single / Multiple / Red Flag
Multiple Avalanches
Advisory Year