22-23

snowpack is becoming stronger

Date
Activity
Snowmobiling

I am finding very solid snowpack in most areas. We dug one pit yesterday that exhibited two weak layers in the top 35cm and one near the ground. This was a wind loaded slope with HN 230cm. CT test did not fail. No evidence of surface hoar at this location. 9100 feet on a NE aspect.
At lower elevations I found evidence of surface hoar forming, but not necessarily on the snow, see photo.

We are entering a warming trend, which is generally healthy for the snowpack. The conditions are right for surface hoar development; however, I am only finding very isolated evidence of this. Something to keep an eye out for.

We have several weak layers in the snowpack that could fail causing an avalanche, likely a large deadly avalanche. It's hard to find places that exhibit reactive test results, but the evidence is in recently human triggered avalanches. We are not getting a ton of new snow and together with the mild temperatures this will create a strong snowpack over time. The places to watch out for are shallower snowpack areas where the persistent weak layer is easier to trigger.  

Region
Island Park
Location (from list)
Sawtelle Peak
Observer Name
Bret Rasmussen

GNFAC Avalanche Forecast for Sun Jan 8, 2023

Snowpack and Avalanche Discussion

<p><span><span><span><span><span><span>A person can trigger avalanches that break on weak layers buried 1-4 feet deep, or avalanches that involve recently wind-drifted snow. Yesterday, on Buck Ridge near Big Sky a snowboarder triggered a small avalanche on a wind-loaded slope and was partially buried to their waist (</span></span></span></span></span></span><a href="https://www.mtavalanche.com/images/23/snowboarder-caught-small-slide"><…;), and Skiers in the northern Bridger Range saw a recent large natural avalanche that broke 1-2 feet deep and 100 feet wide (</span></span></span></span></span></span><a href="https://www.mtavalanche.com/images/23/snowboarder-caught-small-slide"><…;). Two days ago, a very large avalanche on Saddle Peak broke 550 feet wide and almost 2 feet deep on a buried weak layer (</span></span></span></span></span></span><a href="https://www.mtavalanche.com/images/23/crown-close-saddle-peak"><span><s… of crown up close</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span>). It caught and partially buried a person who was hitting a jump in the runout zone (</span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/27536"><span><span><span><strong><span… and details</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>Carefully assess the snowpack for buried weak layers and avoid steep slopes where you suspect they exist. Buried weak layers are not consistently showing instability in our snowpack tests, but avalanche activity over the past week is a clear sign that large avalanches can be triggered. The fatal avalanche last weekend near Cooke City should provide good motivation to take buried weak layers seriously (</span></span></span></span></span></span><a href="https://www.mtavalanche.com/accident/22/12/31"><span><span><span><stron… report</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span>). Be extra cautious of wind-loaded slopes and slopes where snow depth is variable where a large avalanche may be triggered from a relatively shallow spot. Look for cracks across the snow surface around your skis or sled as a sign that recently drifted snow remains unstable.&nbsp;</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>Today, human-triggered avalanches are possible and the avalanche danger is MODERATE.</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>Please share avalanche, snowpack or weather observations via our</span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/add/snow_obs"><span><span><span><span>…; </span></span></span></span></span></span><span><span><span><strong><span><u><span><span>website</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span>, email (</span></span></span></span></span></span><span><span><span><strong><span><span>mtavalanche@gmail.com</span></span></strong></span></span></span><span><span><span><span><span><span>), phone (406-587-6984), or Instagram (#gnfacobs).</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>In Island Park a person can trigger avalanches that break deep and wide on buried weak layers, or avalanches that involve recently wind-drifted snow. Carefully assess the snowpack for buried weak layers and avoid steep slopes where you suspect they exist.&nbsp; If snow starts to accumulate early today, fresh drifts may form that could avalanche. Look for cracks across the snow surface around your skis or sled as a sign that drifted snow is unstable.</span></span></span></span></span></span></p>

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Snowboarder triggered/caught small slide on Buck Ridge

Buck Ridge
Southern Madison
Code
SS-ARu-R2-D1.5-I
Elevation
9200
Aspect
NE
Latitude
45.17190
Longitude
-111.38000
Notes

Location: 45.165, -111.35808 (onX) 

Elevation: ~9,200 feet

While riding a small NNE facing slope near the trail on Buck Ridge, a snowboarder triggered and followed a cornice slide that propagated approximately 75 feet and slid about 20' vertical. The one rider was caught and carried approx. 10' and ended up buried upright, waist deep with no injuries. 

 

Number of slides
1
Number caught
1
Number buried
1
Avalanche Type
Soft slab avalanche
Trigger
Snowboarder
Trigger Modifier
u-An unintentional release
R size
2
D size
1.5
Bed Surface
I - Interface between new and old snow
Problem Type
Wind-Drifted Snow
Slab Thickness
10.0 inches
Vertical Fall
20ft
Slab Width
75.00ft
Slab Thickness units
inches
Single / Multiple / Red Flag
Single Avalanche
Advisory Year

From obs: "While riding a small NNE facing slope near the trail on Buck Ridge, a snowboarder triggered and followed a cornice slide that propagated approximately 75 feet and slid about 20' vertical. The one rider was caught and carried approx. 10' and ended up buried upright, waist deep with no injuries."

 

Southern Madison, 2023-01-08

From obs: "While riding a small NNE facing slope near the trail on Buck Ridge, a snowboarder triggered and followed a cornice slide that propagated approximately 75 feet and slid about 20' vertical. The one rider was caught and carried approx. 10' and ended up buried upright, waist deep with no injuries."

 

Southern Madison, 2023-01-08

Natural Avalanche near Fairy Lake

Fairy Lake
Bridger Range
Code
HS-N-R2-D2-O
Elevation
9000
Aspect
NE
Latitude
45.90430
Longitude
-110.95800
Notes

From IG 1/7/23: "Natural slide in avalanche bowl up in fairy lake today."

Number of slides
1
Number caught
0
Number buried
0
Avalanche Type
Hard slab avalanche
Trigger
Natural trigger
R size
2
D size
2
Bed Surface
O - Old snow
Problem Type
Persistent Weak Layer
Slab Thickness
24.0 inches
Vertical Fall
1000ft
Slab Width
200.00ft
Snow Observation Source
Slab Thickness units
inches
Single / Multiple / Red Flag
Single Avalanche
Advisory Year