Debris from a natural avalanche that skiers watched happen on Sunday 1/27. Photo: A. Whitmore
Avalanche Details: Natural slides near Emigrant
Out of Advisory Area, 2019-01-28
18-19
GNFAC Avalanche Forecast for Mon Jan 28, 2019
Snowpack and Avalanche Discussion
<p>Yesterday was the tenth day in a row with reports of natural or human triggered avalanches. More than sixteen natural and human triggered slides were reported on Saturday and Sunday (<u><strong><a href="https://www.mtavalanche.com/avalanche-activity">avalanche activity</a></strong></u>).<strong> </strong>Sadly, on Friday a skier was killed in an avalanche in the Tobacco Roots (<u><strong><a href="https://www.mtavalanche.com/node/19826">details and photos</a></strong></u>). Doug and I visited the site during the rescue and will have a detailed report available shortly. On Saturday, two skiers triggered separate avalanches in the Bridger Range. One skier was caught and fully buried during the slide, but ended up on top of the debris (<u><strong><a href="https://www.mtavalanche.com/node/19852">details</a></strong></u>). The other was not caught (<u><strong><a href="https://www.mtavalanche.com/node/19873">details</a></strong></u>).</p>
<p>Yesterday, skiers on Mt. Ellis unintentionally triggered a large avalanche while skinning through tight trees. They were not caught, but too close for comfort. They had experienced several “pop and drop” collapses on the way in and decided to avoid open, steep slopes. The avalanche was 2’ deep, 100’ wide and ran 500’ through deadly, high consequence terrain (<u><strong><a href="https://www.mtavalanche.com/node/19903">photos and details</a></strong></u>). Karl was there the day before and found very unstable conditions (<u><strong><a href="https://www.youtube.com/watch?v=zHramxEhjO8&index=2&list=PLXu51…;). This is the third avalanche this weekend that broke and ran through dense trees (<u><strong><a href="https://www.mtavalanche.com/node/19877">details</a></strong></u>), including the fatal slide on Friday. There have also been multiple reports of slides on lower angle avalanche terrain, just over 30 degrees steep (<u><strong><a href="https://www.mtavalanche.com/node/19857">details</a></strong></u>). Large avalanches breaking on lower angle and treed terrain indicate very dangerous and unstable conditions. Many of these slopes we often see as safe, but can actually be deadly.</p>
<p>If you travelled in the backcountry this weekend you probably experienced collapsing, got unstable test results, or saw an avalanche. Ian and his partner were at Taylor Fork yesterday and triggered an avalanche from flat terrain above (<strong><a href="https://www.youtube.com/watch?v=hh3eSrv6fYI&index=2&t=0s&li…;, <u><strong><a href="https://www.mtavalanche.com/images/19/sunlight-basin-avalanche-2">photo…;)<strong>.</strong> Avalanche Danger has been considerable for the past week meaning natural avalanches are possible and human triggered avalanches likely. Either or both types were reported every day. While avalanche danger and likelihood of avalanches has stayed constant, the size and consequences of avalanches has increased. Getting caught in an avalanche today will be unforgiving.</p>
<p>Before you go to the backcountry do your homework. Carefully plan safe routes through low angle terrain, along ridgelines and far away from the bottom of steep slopes. View our <u><strong><a href="https://www.youtube.com/playlist?list=PLXu5151nmAvRNl9kuY3DxfWN1qiU7IeX…;, <u><strong><a href="https://www.mtavalanche.com/photos">photos</a></strong></u>, and <u><strong><a href="https://www.mtavalanche.com/avalanche-activity">avalanche activity</a></strong></u><strong> </strong>pages for a more thorough understanding of the snowpack. Today large and dangerous avalanches are easy to trigger and could break naturally. Avalanche danger is <strong>CONSIDERABLE</strong>.</p>
<p>If you get out and have any avalanche or snowpack observations to share, contact us via our <u><a href="https://www.mtavalanche.com/node/add/snow_observation">website</a></u>, email (<u><a href="mailto:mtavalanche@gmail.com">mtavalanche@gmail.com</a></u>), phone (406-587-6984), or Instagram (#gnfacobs).</p>
Avalanche Fatality Tobacco Root Mountains
On Friday four skiers were caught in an avalanche while ascending a steep forested slope in the Tobacco Root Mountains. Two skiers grabbed trees and were able to self-arrest, the other two skiers were swept downhill. One skier was seriously injured, the other died from trauma. Doug and Alex visited the site and we will issue more information once it becomes available. Our deepest condolences go to the family and friends of the victim.
Remote triggered near Black Butte
Black Butte- Gravelly Range
Out of Advisory Area
Code
SS-AMr-R3-D2-G
Latitude
44.90450
Longitude
-111.85600
Notes
Snowmobilers reported triggering multiple avalanches from low slope angles between West Fork and Black Butte in the Gravelly Range. Photo: S. Olson
Multiple Avalanches
Number caught
0
Number buried
0
Number killed
0
Avalanche Type
Soft slab avalanche
Trigger
Snowmobile
Trigger Modifier
r-A remote avalanche released by the indicated trigger
R size
3
D size
2
Bed Surface
G - Ground
Problem Type
Persistent Weak Layer
Slab Thickness units
centimeters
Single / Multiple / Red Flag
Multiple Avalanches
Advisory Year
Natural slides near Emigrant
Arrastra Creek
Out of Advisory Area
Code
SS-N-D2.5
Aspect
SE
Notes
Skiers reported multiple large natural avalanches in the Arrastra drainage in the Absarokas. They estimated the recent storm cycle totals to be 3-5'.
From e-mail: "We observed a rather large natural slide come down within a 100' of us as we were beginning our ascent in some thick old-growth Douglas Fir woods next to the terminus of a large south-facing gully/slide path.
we knew there was a party of at least two above us. I quickly put my beacon in search mode and scanned the toe of the debris. No signals. We separated by a safe distance and I led up the skin track which bordered the lower 400' of the debris field with my beacon in search mode. No signals. At 400' up the Arrastra Road crosses the path. At this point my partner and I met up. I crossed the debris angling downhill to the west continuing to search for any potential signals. No signals. I skinned up the remaining west border of the path in search mode. Back at the road I finally heard and saw the other party of 3 come out of the woods above us. Very relieved we were. They thanked us for our concern and we all descended and left for the day.
Since last Friday I would realistically say that 3'-5' of new snow had accumulated. I'd been in here Mon.-Fri. this week and aside from Tuesday it had been snowing at high rates at all times.
This particular path had slid to within 300' of the upper road around New Year's. It is a south facing path with two distinct gullies and runs from just under 10000' down to 7600'.
Quite a few other large crowns were observed higher in the bowls, mostly being confined to storm snow. But I'm sure some were failing on PWLs at the ground and within the snowpack."
Number caught
0
Number buried
0
Number killed
0
Avalanche Type
Soft slab avalanche
Trigger
Natural trigger
D size
2.5
Problem Type
New Snow
Images
Slab Thickness units
centimeters
Single / Multiple / Red Flag
Single Avalanche
Advisory Year
Skiers reported multiple large natural avalanches in the Arrastra drainage in the Absarokas. They estimated the recent storm cycle totals to be 3-5'. Photo: A. Whitmore
Avalanche Details: Natural slides near Emigrant
Out of Advisory Area, 2019-01-27
Naturals, collapsing, propagating - Main Fork Hyalite
Hyalite - main fork
Northern Gallatin
Code
N
Latitude
45.45880
Longitude
-110.95700
Notes
A group of skiers observed propagation in their stability tests and experienced collapsing in the main fork today. A separate group of ice climbers heard two different natural avalanches and observed active wind loading at higher elevations. A climber from a third group watched a natural avalanche next to the Mummy.
Multiple Avalanches
Number caught
0
Number buried
0
Number killed
0
Trigger
Natural trigger
Slab Thickness units
centimeters
Single / Multiple / Red Flag
Multiple Avalanches
Advisory Year
We triggered this avalanche remotely from about 50 feet above the crown up on the ridge. The crown was 1-2' deep, 100' wide, and ran between 200 and 300 vertical feet through trees and cliffs. Another slide failed sympathetically at the same time, 100' down the ridgeline. The slides failed on a 40 cm thick layer of depth hoar, which composed half of the snowpack. Photo: GNFAC
Avalanche Details: Remote Triggered at Sunlight Basin (Taylor Fork)
Southern Madison, 2019-01-27
Remote Triggered at Sunlight Basin (Taylor Fork)
Sunlight Basin
Southern Madison
Code
SS-AFr-R2-D2-O
Elevation
9500
Aspect
SE
Aspect Range
E-SE
Latitude
44.97560
Longitude
-111.31300
Notes
We triggered these avalanches remotely, about 50 feet above the crown up on the ridge. Each crown was 1-2' deep, 100' wide, and both slides ran between 200 and 300 vertical feet through trees and cliffs. The slides failed on a 40 cm thick layer of depth hoar, which composed half of the snowpack. Photo: GNFAC
Multiple Avalanches
Number caught
0
Number buried
0
Number killed
0
Avalanche Type
Soft slab avalanche
Trigger
Foot penetration
Trigger Modifier
r-A remote avalanche released by the indicated trigger
R size
2
D size
2
Bed Surface
O - Old snow
Problem Type
Persistent Weak Layer
Slab Thickness
18.0 centimeters
Vertical Fall
300ft
Slab Width
100.00ft
Weak Layer Grain type
Large striated crystals
Weak Layer grain size
4.00mm
Weak Layer Hardness
F-
Slab Layer Grain Type
Decomposing and Fragmented precipitation particles
Slab Layer Hardness
F+
Attached Videos
Slab Thickness units
centimeters
Single / Multiple / Red Flag
Multiple Avalanches
Advisory Year