21-22

Snowpit Blackmore Shoulder

Date
Activity
Skiing

We dug a snow pit on an E facing slope NTL and found a non-reactive, layered snowpack. We got a score of 22 on our ECT with no propagation on what is presumably a new-old snow interface, where the newer snow was on top of wind effected older snow. We did no other tests. 

We also found a thin to medium wind crust (1-5cm) on east and northerly slopes ATL. Our descent took us down the SE face and off the opposite shoulder from our snow pit down a north-facing chute. There was an obvious wind effect on the snow surface and we found the same wind crust/slab. Upon a ski cut, I released a very small slab that entrain a decent about of snow by the time it stopped ~600 vert. feet lower. It was the thin wind slab sliding on softer snow underneath. There was an already reported, similar avalanche from the same day higher on the face of Blackmore that ran a bit further and bigger. It seems like it had pretty much the same characteristics. 

Region
Northern Gallatin
Location (from list)
Mt Blackmore
Observer Name
Wyatt Gober

GNFAC Avalanche Forecast for Mon Feb 28, 2022

Snowpack and Avalanche Discussion

<p>Recent strong wind out of the southwest-west drifted snow into 6-18” thick hard slabs on top of weak, sugary snow. These wind slabs are possible for a skier or rider to trigger today. Yesterday skiers in Hyalite and the southern Gallatin Range had shallow wind slabs crack wide under their skis (<a href="https://www.mtavalanche.com/node/26024"><strong><u>photos and details</u></strong></a>). On Saturday in the northern Bridgers three separate groups of skiers triggered slabs of wind-drifted snow 8-18” deep, some were hundreds of feet wide. One person was caught, but unharmed (<a href="https://www.mtavalanche.com/node/25997"><strong><u>details and photos</u></strong></a>, <a href="https://www.mtavalanche.com/node/25992"><strong><u>details and photos</u></strong></a>, <a href="https://www.mtavalanche.com/node/25989"><strong><u>details and photos</u></strong></a>). On Baldy Peak a skier triggered a similar hard slab, 6” deep and 100’ wide (<a href="https://www.mtavalanche.com/node/26026"><strong><u>photo</u></strong></…;). These and other recent avalanches are evidence that an unstable snowpack can be found on wind-loaded slopes near Bozeman, Big Sky and West Yellowstone (<a href="https://www.mtavalanche.com/node/25999"><strong><u>Mt. Blackmore photo</u></strong></a>, <a href="https://www.mtavalanche.com/images/22/fresh-wind-slab-near-summit-blaze… Mtn. photo</u></strong></a>, <a href="https://www.mtavalanche.com/images/22/snowmobile-triggered-slides-teepe… Basin photo</u></strong></a>).&nbsp;</p>

<p>On wind-loaded slopes avalanches are possible and avalanche danger is MODERATE. Without recent drifts of snow,&nbsp;avalanches are unlikely&nbsp;and danger is LOW on non-wind loaded slopes. Dave skied in Specimen Creek yesterday and found a weak snowpack that needed a slab on top to be unstable (<a href="https://www.youtube.com/watch?v=nHauGuzZ7pk&amp;list=PLXu5151nmAvT1nrM2…;). Before riding on steep slopes carefully assess the potential for wind-loading and buried weak layers.</p>

<p>Yesterday my partners and I rode north of Cooke City and saw&nbsp;five recent skier and rider triggered slides. Most were small soft slabs (<a href="https://www.mtavalanche.com/node/26017&quot; title="photo and details"><strong><u>photo and details</u></strong></a><strong>, </strong><a href="https://www.mtavalanche.com/images/22/snowmobile-triggered-near-goose-c…;) and one hard slab broke more than 3 feet deep (<a href="https://www.mtavalanche.com/images/22/snowmobile-triggered-hard-slab-ne…;). While touring up a slope we collapsed the snowpack and heard a “whumph” under our skis. We dug and found a layer of weak snow buried 8-10” deep which created the instability (<a href="https://www.youtube.com/watch?v=SxPaEcKATts&amp;list=PLXu5151nmAvT1nrM2…;). This setup makes avalanches possible to trigger. These slides will probably be small, and are most hazardous if they push you into trees or off a cliff. Continued strong southwest-west wind today will grow larger slabs and add weight to deeper buried weak layers.&nbsp;</p>

<p>Triggering an avalanche on weak snow buried 2 feet deep is much less likely than it was a week ago, but the consequences of being caught are potentially deadly. Examples of this type of avalanche are two large snowmobiler triggered avalanches last weekend, one of which was fatal (<a href="https://www.youtube.com/watch?v=qC7geA4kgyg&amp;list=PLXu5151nmAvT1nrM2… Mountain fatality video</u></strong></a>, <a href="https://www.youtube.com/watch?v=LHkbEAf1rlM&amp;list=PLXu5151nmAvT1nrM2…. Abundance video</u></strong></a>, <a href="https://www.mtavalanche.com/node/25941"><strong><u>details</u></strong>…;). Before you travel on steep slopes, carefully assess the snowpack for potential instabilities and consider the consequences of being caught in a slide. Strong wind will drift snow today and make large avalanches possible. The avalanche danger is MODERATE on wind-loaded slopes. On non-wind loaded slopes avalanche danger is LOW because avalanches will be small or are unlikely, but not impossible.</p>

<p>If you get out, please send us your observations no matter how brief. You can submit them via our <a href="https://www.mtavalanche.com/node/add/snow_observation"><strong><u>websi…;, email (<a href="mailto:mtavalanche@gmail.com"><strong><u>mtavalanche@gmail.com</u></str…;), phone (406-587-6984), or Instagram (#gnfacobs).</p>

Upcoming Education Opportunities

See our education calendar for an up-to-date list of all local classes. Here are a few select upcoming events.

March 4, Companion Rescue Clinic with the Bozeman Splitfest. Information and registration HERE.

From obs. 2/27/22: "... on our way up Flanders. Near ridge line there’s a 3-4”, dense wind slab that was quite touchy. I chucked a basketball size piece of cornice onto a small test slope and observed it collapse and crack." Photo: S. Gill

Avalanche Details: Shooting Cracks in Hyalite and Specimen Creek
Forecast link: GNFAC Avalanche Forecast for Mon Feb 28, 2022GNFAC Avalanche Forecast for Wed Mar 2, 2022
Northern Gallatin, 2022-02-28
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    • Wind Slab and surface hoar in Flanders area

    Date
    Activity
    Skiing

    Found 2-4 mm SH on our way up Flanders. Near ridge line there’s a 3-4”, dense wind slab that was quite touchy. I chucked a basketball size piece of cornice onto a small test slope and observed it collapse and crack. 

    Region
    Northern Gallatin
    Location (from list)
    Flanders Creek
    Observer Name
    S Gill

    Skier triggered shallow wind slab on Baldy

    BRIDGER RANGE
    Bridger Range
    Code
    HS-AS-R1-D1-O
    Elevation
    8300
    Aspect
    NE
    Latitude
    45.85120
    Longitude
    -110.94800
    Notes

    From message 2/27/22: "Skier triggered yesterday in a northeast wind loaded pocket on baldy in S Bridgers. About 6 inches deep and 100ft wide.
    Quite a bit of shooting and cracking elsewhere at lower elevations. Felt wind loaded just about everywhere after those east winds."

    Number of slides
    1
    Number caught
    0
    Number buried
    0
    Avalanche Type
    Hard slab avalanche
    Trigger
    Skier
    R size
    1
    D size
    1
    Bed Surface
    O - Old snow
    Problem Type
    Wind-Drifted Snow
    Slab Thickness
    6.0 inches
    Slab Width
    100.00ft
    Images
    Skier triggered shallow wind slab on Baldy
    Slab Thickness units
    inches
    Single / Multiple / Red Flag
    Single Avalanche
    Advisory Year
    21-22

    From message 2/27/22: "Skier triggered yesterday in a northeast wind loaded pocket on baldy in S Bridgers. About 6 inches deep and 100ft wide.
    Quite a bit of shooting and cracking elsewhere at lower elevations. Felt wind loaded just about everywhere after those east winds." Photo: J. Keogh

    Avalanche Details: Skier triggered shallow wind slab on Baldy
    Forecast link: GNFAC Avalanche Forecast for Mon Feb 28, 2022GNFAC Avalanche Forecast for Wed Mar 2, 2022
    Bridger Range, 2022-02-28
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    • Shooting Cracks in Hyalite and Specimen Creek

    Specimen Creek
    Southern Gallatin
    Code
    HS
    Latitude
    45.03790
    Longitude
    -111.06000
    Notes

    From obs 2/27/22: "Shooting cracks in a thin wind slab on a ridge crest. The slab was small but the collapse was abrupt and propagated 20 feet."

    From a group on Flanders Mtn in Hyalite: "I triggered a shallow 2-3cm deep windslab about 20 feet wide just below the ridgeline. I was not on a steep slope, so it barely moved. "

    Number of slides
    0
    Number caught
    0
    Number buried
    0
    Avalanche Type
    Hard slab avalanche
    Images
    Cracking wind slab below ridge on Flanders
    Shooting Cracks in Specimen Creek 2
    Shooting Cracks in Specimen Creek
    Small windslab triggered on Flanders
    Slab Thickness units
    centimeters
    Single / Multiple / Red Flag
    Red Flag
    Advisory Year
    21-22
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