22-23

Natural large point release north of Bridger

Bradley Meadow
Bridger Range
Code
L-N-R2-D2-O
Elevation
7500
Aspect
SE
Latitude
45.83220
Longitude
-110.92800
Notes

From BBSP: "North of our boundary a natural avalanche was observed on the south end of the lower Bradley's Meadows ridge.  A point release originated in the south facing cliffs.  When it hit the steep knob above the gully it pulled the facets off of the rocks and willows, depositing an approx 4ft deep pile of debris.  There were old tracks on the slope and no one was caught."

Number of slides
1
Number caught
0
Number buried
0
Avalanche Type
Loose-snow avalanche
Trigger
Natural trigger
R size
2
D size
2
Bed Surface
O - Old snow
Problem Type
Persistent Weak Layer
Slab Thickness units
centimeters
Single / Multiple / Red Flag
Single Avalanche
Advisory Year

GNFAC Avalanche Forecast for Thu Dec 29, 2022

Snowpack and Avalanche Discussion

<p><span><span><span><span><span><span>The avalanche warning in Lionhead has expired. Yesterday, Ian and I rode into Taylor Fork to analyze the snow (</span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/27376"><span><span><span><strong><span… and video</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span>). There are 2 weak layers: one about a foot from the surface (</span></span></span></span></span></span><a href="https://youtu.be/F8HKebJ_OJA"><span><span><span><strong><span><u><span>…; </span></span></span></span></span></span><a href="https://www.mtavalanche.com/images/22/new-weak-layer-lionhead"><span><s…;) and another in the lower third of the snowpack. Both consist of sugary facets with the upper layer being the most unstable. Our stability tests bore this out with the upper layer easily breaking, but the real evidence was an avalanche in Sage Basin and a large whumpf (collapse) from our body weight.&nbsp; Visibility was poor, yet this one avalanche confirmed that slopes are dangerous. The same unstable ingredients exist in </span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/27323"><span><span><span><strong><span…; and </span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/27364"><span><span><span><strong><span… Rind</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>It is not unusual to have avalanche deaths the day after an avalanche warning. While the snowpack is </span></span></span></span></span></span><span><span><span><span><em><span>a little</span></em></span></span></span></span><span><span><span><span><span><span> more stable, folks tend to lose their minds in the fresh powder and sunshine. Stay focused and realize that traveling in avalanche terrain today carries significant risk. Triggering avalanches remains likely and the avalanche danger is rated CONSIDERABLE on all slopes. </span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>The mountains around Cooke City have a weak layer of faceted snow buried 1-2 feet under the surface. These sugary grains do not stick together and are breaking in stability tests (</span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/27365"><span><span><span><strong><span…;), and more significantly, avalanched on a small slope that was intentionally triggered by a snowboarder on Monday (</span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/27341"><span><span><span><strong><span… and photos</span></span></u></span></strong></span></span></span></a><span><span><span><span><span><span>). These mountains also have a weak layer near the ground that could be triggered from thin snow cover. An avalanche breaking deep would be large and deadly. In general, releasing avalanches on either of these layers is possible, just not on most slopes. This is our conundrum: riding on steep slopes without consequence does not indicate stability. Be careful, only ride or ski one at a time, and look for signs of instability (cracking, collapsing, recent avalanches, poor stability test scores). For today, the avalanche danger is rated MODERATE on all slopes. </span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>The mountains around Bozeman and Big Sky have 2 layers of sugary, faceted snow on many slopes. One is a foot under the surface and another is near the ground. On Monday, skiers near Big Sky triggered a collapse (whumpf) which is a sign of instability (</span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/27334"><span><span><span><strong><span…;). Skiers also found unstable snow on Divide Peak yesterday (</span></span></span></span></span></span><a href="https://www.mtavalanche.com/node/27368"><span><span><span><strong><span…;) which matched Dave’s findings on Mt. Blackmore (</span></span></span></span></span></span><a href="https://youtu.be/jjrqrzYhpIc"><span><span><span><strong><span><u><span>…;) and Alex’s field day on Buck Ridge (</span></span></span></span></span></span><a href="https://www.youtube.com/watch?v=C2HXtmgNkt8"><span><span><span><strong>…;). Tuesday’s snow and strong wind has loaded these weak layers. Dig and assess steep slopes, and only expose 1 person at a time to avalanche terrain. For today, triggering avalanches is possible and the danger is rated 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).&nbsp;</span></span></span></span></span></span><span><span><span><span><span><span>&nbsp;</span></span></span></span></span></span></p>

<p><span><span><span><span><span><span>The avalanche warning in Island Park has expired. Weak layers in the snowpack remain dangerous. It is not unusual to have avalanche deaths the day after an avalanche warning. While the snowpack is </span></span></span></span></span></span><span><span><span><span><em><span>a little</span></em></span></span></span></span><span><span><span><span><span><span> more stable, folks tend to lose their minds in the fresh powder and sunshine. Stay focused and realize that traveling in avalanche terrain today carries significant risk. </span></span></span></span></span></span></p>

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Snowpit in Beehive

Date
Activity
Skiing

Today in Beehive we found blowing snow which has grown the easterly cornices significantly since two days prior when we were there as well as pillows of wind drifted snow on leeward slopes. In wind protected locations we found excellent skiing. Previous tracks were filled in with right side up snow that seemed to be bonding well to the previous snow surface. In our pit on a east aspect at 9,000' we found two very thin melt freeze crusts in the top 30cm that produced ECTN as well as facets on the ground that produced no results. On a west aspect we felt that same melt freeze crust buried under the new snow breaking and hooking up our skis. A quick hand pit showed this crust to be a little thicker and harder.

Region
Northern Madison
Location (from list)
Beehive Basin
Observer Name
Jackson

Natural Avalanche in Sage Basin

Taylor Fork
Southern Madison
Code
SS-N-R1-D1-O
Elevation
9000
Aspect
N
Latitude
45.06070
Longitude
-111.27200
Notes

This natural avalanche looks to have broken about 1 foot deep and stepped down to the ground on the steeps. It likely released during the storm.

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
O - Old snow
Problem Type
Persistent Weak Layer
Slab Thickness
12.0 inches
Vertical Fall
100ft
Slab Width
150.00ft
Weak Layer Grain type
Faceted Crystals
Snow Observation Source
Slab Thickness units
inches
Single / Multiple / Red Flag
Single Avalanche
Advisory Year

Avalanches and Instability

Date
Activity
Snowmobiling

Visibility was good enough so we headed into the weather station and dug on the E facing slope. The instability was concerning and we tip-toed out onto the slope with an inclinometer in hand. It was thin (HS 105) and the 2 prominent weak layers were there: ECTP11 on the upper one and ECTP12 on the facets/depth hoar. We then rode into Sage Basin and found natural avalanche activity on the N facing side. It looked like the slope fractured on the upper layer and on steep terrain it broke to the ground. We dug another on the east end of Sage and had a 176 cm deep snowpack that was unremarkable. On the way out we stopped at Consolation Hill (SE facing) and I got a big whumpf with a body slam as footsteps were just sinking to the ground. This snowpack was thin (HS 87) and it broke on the depth hoar at 35 cm (ECTP11).

Region
Southern Madison
Location (from list)
Taylor Fork
Observer Name
Doug Chabot