24-25

GNFAC Avalanche Forecast for Wed Nov 13, 2024

Snowpack and Avalanche Discussion

<p><span><span><span><span><span><span>Over the last month small storms have grown the snow depth to 10-18” at mountain weather stations (</span></span></span></span></span></span><a href="https://www.mtavalanche.com/weather/wx-avalanche-log"><span><span><span… log</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span>). After snowfall a week ago there were skier triggered and natural avalanches (</span></span></span></span></span></span><a href="https://www.mtavalanche.com/avalanche-activity"><span><span><span><stro… activity</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span>). Many of these avalanches were on wind-loaded slopes and broke at the base of the shallow snowpack (</span></span></span></span></span></span><a href="https://www.mtavalanche.com/images/24/old-avalanche-crown"><span><span>… from northern Bridger crown</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span>). Additionally, multiple skiers reported finding weak snow at the bottom of the snowpack in Hyalite, near Big Sky and the Bridger Range (</span></span></span></span></span></span><a href="https://www.mtavalanche.com/snow-observations-list"><span><span><span><… page</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span>). The shallow snowpack changes a lot from day to day, but the avalanches and observations from last week are evidence that it is time to be prepared. Carefully assess the terrain and snowpack for avalanche potential, and carry the proper gear (beacon, shovel, probe).</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>Avalanches are most likely where recent snow has drifted into thicker slabs. On steeper slopes this coincides with the best place to ski or ride because the deeper snowpack provides better coverage of rocks and hazards. Mark describes this early season dilemma in his recent video from </span></span></span></span></span></span><a href="https://www.youtube.com/watch?v=lA02PeWkO6g&amp;list=PLXu5151nmAvToI_ir… Lake</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span>, and advises to give the snow time after the snow falls and wind blows. If you see evidence of recent wind-loading, be patient and ride lower angle or non-wind loaded slopes.</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>The early season snowpack will be the foundation for future storms and is constantly changing. In Mark’s videos from the </span></span></span></span></span></span><a href="https://www.youtube.com/watch?v=W99OEptQWy8&amp;list=PLXu5151nmAvToI_ir… Range</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.youtube.com/watch?v=RGXaUwH-XSA&amp;list=PLXu5151nmAvToI_ir… Park</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span> last weekend, he shows that the snow has become weak from cold temperatures and clear nights. This could lead to fresh drifts being easier to trigger.</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>If you intend to ride or cross steep slopes, watch for signs of instability such as recent avalanche activity, shooting cracks and collapsing. If obvious signs are absent, dig a quick snowpit to assess for instability.</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

Wind sculpting on Thunder Road

Date
Activity
Skiing

Wind sculpting observed along thunder road at Bridger Bowl.

Region
Bridger Range
Location (from list)
Bridger Bowl
Observer Name
Tyler Allen

Natural Avalanche near Fairy Lake

Fairy Lake
Bridger Range
Code
SS-N-R1-D1-G
Elevation
9400
Aspect
N
Latitude
45.90430
Longitude
-110.95800
Notes

From obs: "I made it up to an old crown in a north-facing chute around Fairy Lake at around 9400 ft; it broke the night of 11/6 or the morning of 11/7. It looked like a wind slab that broke on a rotten layer of facets intermixed with scree. Found facets to be fairly widespread through the bottom of the snowpack on the north-facing slopes and surface hoar on most nonsolar slopes." 

Number of slides
1
Number caught
0
Number buried
0
Avalanche Type
Soft slab avalanche
Trigger
Natural trigger
R size
1
D size
1
Bed Surface
G - Ground
Problem Type
Persistent Weak Layer
Slab Thickness
6.0 inches
Snow Observation Source
Slab Thickness units
inches
Single / Multiple / Red Flag
Single Avalanche
Advisory Year

From obs: "I made it up to an old crown in a north-facing chute around Fairy Lake at around 9400 ft; it broke the night of 11/6 or the morning of 11/7. It looked like a wind slab that broke on a rotten layer of facets intermixed with scree. Found facets to be fairly widespread through the bottom of the snowpack on the north-facing slopes and surface hoar on most nonsolar slopes." Photo: J. Alford

Bridger Range, 2024-11-12

From obs: "Toured up into the Blackmore/Elephant basin today to get a sense of the snowpack ahead of the upcoming storm cycle. I poked around and dug in a few spots, trying to observe variations in snow depth and to observe where the snow has been faceting. Every pit I dug, ranging from N to SE facing, had faceting near the ground, all of which reacted in stability tests, if stubbornly. The most interesting test result was an ECTP21 in this layer of basal facets. That pit was dug in a large wind drift. I saw no propagation in any other pit or test.

Northern Gallatin, 2024-11-12