18-19

Snowmobile-triggered slab Northern Bridgers

Fairy Lake
Bridger Range
Code
SS-AM-R1-D1.5-I
Elevation
8500
Aspect
NE
Latitude
45.91380
Longitude
-110.98000
Notes

A skier in the northern Bridgers saw this snowmobile-triggered avalanche after experiencing a large whumpf on a nearby slope. From the email:

"Skied Fraizer Lake, skinning up the north facing in the bowl. It was light snow on a hard surface with good stability until we got up under the cliffs and I started noticing grauple pouring into the skin track . Tested a few more steps and got a big whomph, dug a quick hand pit and got super poor stability with a 6-8" slab on cold grauple. I skied backwards down the track and away. We saw a bunch of big north facing lines get skied, and I was feeling a bit conservative. As we were leaving we checked out Hardscrabble North bowl and saw this 'biler trigged slide the north facing pocket, same aspect as where we were." Photo and obs: P. Cronin

Number of slides
1
Number caught
0
Number buried
0
Number killed
0
Avalanche Type
Soft slab avalanche
Trigger
Snowmobile
R size
1
D size
1.5
Bed Surface
I - Interface between new and old snow
Problem Type
New Snow
Slab Thickness
8.0 inches
Vertical Fall
100ft
Slab Width
25.00ft
Weak Layer Grain type
Graupe
Images
Snowmobile-triggered slab Northern Bridgers
Slab Thickness units
inches
Single / Multiple / Red Flag
Single Avalanche
Advisory Year
18-19

Snowmobile-triggered slide near Fairy Lake on Saturday (3/30). New snow was drifted into small wind slabs that may remain reactive in isolated areas.  Photo: P. Cronin

Avalanche Details: Snowmobile-triggered slab Northern Bridgers
Forecast link: GNFAC Avalanche Forecast for Sun Mar 31, 2019GNFAC Avalanche Forecast for Mon Apr 1, 2019GNFAC Avalanche Forecast for Tue Apr 2, 2019GNFAC Avalanche Forecast for Wed Apr 3, 2019GNFAC Avalanche Forecast for Thu Apr 4, 2019GNFAC Avalanche Forecast for Fri Apr 5, 2019GNFAC Avalanche Forecast for Sun Apr 7, 2019
Bridger Range, 2019-03-30
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    • New snow instability-Blackmore

    Mt Blackmore
    Northern Gallatin
    Code
    SS-ASc-R2-D1.5-I
    Elevation
    10000
    Aspect
    E
    Latitude
    45.44340
    Longitude
    -111.00300
    Notes

    Skiers at Mt. Blackmore saw three flavors of avalanches: dry loose, wet loose, and soft slab . The dry avalanches were triggered intentionally, while the loose wet failed naturally. From the email: 

    "Skied the east face of Mt Blackmore. Stability was good, although small loose dry avalanches were easily triggered with ski cuts.We also saw several small loose wet avalanches that released near cliff bands. The snow was starting to become wet when we left." Photo: N. Salsburg

    Multiple Avalanches
    Number caught
    0
    Number buried
    0
    Number killed
    0
    Avalanche Type
    Soft slab avalanche
    Trigger
    Skier
    Trigger Modifier
    c-A controlled or intentional release by the indicated trigger
    R size
    2
    D size
    1.5
    Bed Surface
    I - Interface between new and old snow
    Problem Type
    New Snow
    Slab Thickness
    6.0 inches
    Vertical Fall
    600ft
    Slab Width
    30.00ft
    Images
    New snow instability-Blackmore
    Slab Thickness units
    inches
    Single / Multiple / Red Flag
    Multiple Avalanches
    Advisory Year
    18-19

    GNFAC Avalanche Forecast for Sat Mar 30, 2019

    Snowpack and Avalanche Discussion

    <p><u>Bridger Range</u> &nbsp;<u>Madison Range</u> &nbsp;<u>Gallatin Range</u> &nbsp;<u>Lionhead Area near West Yellowstone</u>&nbsp;&nbsp;<u>Mountains near Cooke City</u></p>

    <p>The avalanche equation is pretty simple. Stability will start off good this morning but decrease during the day due to rising temperatures and direct sun. The northern mountains have an increased chance of wet loose avalanche activity&nbsp;since they received 4-6” of new snow over the past few days, but the southern mountains will also experience heat/sun induced hazard (<u><strong><a href="https://www.youtube.com/watch?v=-f8al-UsP3s&amp;list=PLXu5151nmAvRNl9ku…;). &nbsp;</p>

    <p>Obvious signs of instability will be easy to recognize. Pin wheels and small point releases are bull’s eye data that instability is on the rise. Wet loose avalanches will start on south and east aspects and progress onto to west facing slopes as the sun climbs higher in the sky (<u><strong><a href="https://www.youtube.com/watch?v=mpk-8hesFaU&amp;list=PLXu5151nmAvRNl9ku…;). Slides will likely stay confined to new snow and not step down or gouge into deeper layers (<u><strong><a href="https://www.mtavalanche.com/images/19/avalanches-confined-new-snow">pho…;). Loose snow slides won’t be exceptionally powerful, but they could push a skier or rider into hazardous terrain such as rocks, trees, or gullies.</p>

    <p>A good way to manage wet snow avalanche problems is by starting backcountry travel early in the morning and finishing before surface snow becomes unstable or move to shadier slopes when signs of instability are present. &nbsp;</p>

    <p>A secondary avalanche&nbsp;concern&nbsp;is wind slabs that have formed beneath upper elevation ridgelines (<u><strong><a href="https://www.mtavalanche.com/images/19/wind-slabs-hyalite-2">photo</a></…;). This problem isn’t widespread, but something to keep an eye out for when exploring high alpine objectives, specifically those facing north through east. &nbsp;</p>

    <p>Today, the avalanche danger will start out <strong>LOW</strong> but rise to <strong>MODERATE</strong> by this afternoon.</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&gt;, email (<u><a href="mailto:mtavalanche@gmail.com">mtavalanche@gmail.com</a></u&gt;), phone (406-587-6984), or Instagram (#gnfacobs).</p>

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