22-23

Thin and Variable in YNP

Date
Activity
Skiing

Thin and variable snow pack in the N Fork (?) Specimen creek drainage. Max depth less than 100cm, min depth bare ground. Active wind loading on exposed ridges, multiple whumphs when skinning over wind loaded, low angle slopes. Decent skiing, albeit thin, on low angle W aspects from 8200’ down. 

Region
Southern Gallatin
Location (from list)
Specimen Creek
Observer Name
G. Stevens

GNFAC Avalanche Forecast for Sun Dec 18, 2022

Snowpack and Avalanche Discussion

<p><span><span><span><span><span><span>Last Wednesday and Thursday the mountains near Bozeman and Big Sky received 1-2 feet of low density snow. This snow was blown into thick drifts by moderate to strong westerly wind which shifted to southwest yesterday. Recently formed drifts are 1-4 feet deep, and can break under the weight of a person and avalanche on steep slopes. On Friday, on Saddle Peak a skier triggered an avalanche in wind-drifted snow that broke 2-4 ft deep and 150 ft wide (</span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/27226"><span><span><span><strong><span… and photo</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span>). He was carried almost 500 feet and luckily was not buried or injured. Yesterday, skiers in Hyalite saw recent natural avalanches of wind-drifted snow (</span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/27244"><span><span><span><strong><span… and details</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span>). Be cautious of steep wind-loaded slopes, especially where an avalanche would carry you into consequential terrain like over cliffs or into trees.</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>We have found buried weak, sugary snow on most slopes. Yesterday we found this weak snow in the northern Bridger Range (</span></span></span></span></span></span><a href="https://www.youtube.com/watch?v=DbeAdSSJUqM&amp;list=PLXu5151nmAvTi1DBS…;), and earlier in the week we found it on Buck Ridge (</span></span></span></span></span></span><a href="https://www.youtube.com/watch?v=En1DxtBkHt0"><span><span><span><strong>…;) and Mt. Ellis (</span></span></span></span></span></span><a href="https://youtu.be/TkUux4F7dV8"><span><span><span><strong><span><u><span>…;). This weak layer can cause avalanches to break deeper and wider, so it is worth digging to look for and assess before traveling on any steep slope.</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>Weak layers of sugary snow buried 2-4 feet deep, and deeper on wind-loaded slopes, make large avalanches possible for a person to trigger today. Since nearly 3 weeks ago when these layers were buried, we have seen natural and human-triggered avalanches large enough to bury a person, and some large enough to break trees or destroy a car (</span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/27218"><span><span><span><strong><span… avalanches last week near Cooke</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span>, </span></span></span></span></span></span><a href="http://www.mtavalanche.com/index.php/node/27148"><span><span><span><str…; from an avalanche triggered from below last week).&nbsp;</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>Without much recent snow and wind-loading, the likelihood is slowly decreasing for triggering an avalanche on these weak layers, but the consequences remain large. Be extra cautious of travel on and underneath slopes steeper than 30 degrees. The safest strategy is to avoid steep slopes, especially those that are heavily wind-loaded. If you choose to ski or ride steep slopes, choose terrain that doesn’t have drifted snow and dig to check for the presence of buried weak layers. Avalanches are possible to trigger and avalanche danger is MODERATE.&nbsp;</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>If you get out, 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>

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Natural Wind slabs in Hyalite

Maid of the Mist
Northern Gallatin
Code
SS-N-R1-D1.5-I
Elevation
9600
Aspect
NE
Latitude
45.41640
Longitude
-110.97000
Notes

Went on a tour today with a buddy and traveled through twin falls basin as well as the maid. We skied a NW slope off of Palace Butte and found touchy conditions below the ridge line, but great skiing in the trees. We also skied the bowl of Arden peak. We observed numerous recent wind slabs that released naturally in the past 24 hours on NE and E aspects with some crowns starting to get covered up throughout the day. Judging from afar, I would estimate these crowns to be 6 inches to 1.5 feet deep. 

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
Bed Surface
I - Interface between new and old snow
Problem Type
Wind-Drifted Snow
Slab Thickness
8.0 inches
Vertical Fall
300ft
Slab Width
75.00ft
Snow Observation Source
Slab Thickness units
inches
Single / Multiple / Red Flag
Single Avalanche
Advisory Year

From 12/17: "We observed numerous recent wind slabs that released naturally in the past 24 hours on NE and E aspects with some crowns starting to get covered up throughout the day. Judging from afar, I would estimate these crowns to be 6 inches to 1.5 feet deep." Photo: Tommy S.

Northern Gallatin, 2022-12-18