Bollettino valanghe

Salt River and Wyoming Ranges

Bridger-Teton Avalanche Center
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Pericolo valanghe

Fri
Alta quota
4 · Forte
Limite del bosco
3 · Marcato
Sotto il limite
3 · Marcato
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In sintesi

It is very easy to trigger a large avalanche 1-3 feet thick, particularly in steep, wind loaded terrain.  Avalanches are most likely to occur without a human trigger at upper elevations where wind has drifted snow.  Large natural avalanches have been reported already this morning due to rapid loading of new snow.  

Problemi valanghivi

  • Wind Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Likely
    Dimensione
    1–2

    New, light density snow has been easy to move by the wind in the past 36 hours. The critical point is that heavy snow and wind will continue to ramp up this morning.  Wind exposed areas with signs of drifting are the most likely to be triggered.  Evaluate the new snow carefully, even in wind-sheltered areas, for shooting cracks due to the potentially upside-down nature of the upper snowpack. The 6-10" of 5% density snow that fell yesterday is being covered today by denser and heavier snow.  These storm slabs are most likely to be found in the Palisades and Gros Ventres.

  • Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1.5–2.5

    Weak snow was buried 1-3 feet below a cohesive slab of snow that accumulated last week and wll now be covered by 1-2' of snow from yesterday and today. This avalanche problem has been is gaining strength in many locations but will be tested today with the new load of snow. You are most likely to trigger this persistent slab avalanche in steep, wind loaded terrain on west through north through east aspects. Watch out for rocky areas, cliffs and thin convexities where you will more easily impact the weak layer.  Look for pillows, drifts and signs of wind loading where the persistent slab problem is further stressed and easier to trigger.

    In steep terrain, watch for loose dry snow avalanching. This problem can entrain more snow than you think and has the potential to knock you off your feet or possibly impact deeper weak layers in the snowpack.

     

    (2/12/2024)

    Avalanche near Blind Bull 9100' N aspect steep 37deg slopes

    Photo: Alex Drinkard

  • Deep Persistent Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    2–3

    Weak snow from December was buried in early January. In areas of the Greys zone with a deeper snowpack like the Salt River and Snake River zones, this weak layer is 3-5 feet deep. We have not seen an avalanche fail on this layer in areas with a deeper snowpack and it will take a very large trigger, such as an avalanche or cornice drop for this to happen. In parts of the zone with a more shallow snowpack (parts of the Wyoming Range, Hoback, Palmer Creek, and Little Greys), this weak layer can be more easily impacted. You are most likely to find this problem on west through north through east aspects. If no avalanches occur on this layer during this period of heavy snow and wind through Friday, the deep weakness will be dormant until significant heating and melting.

    (2/12/2024)

    Two avalanches pictured off Prospect Peak. The avalanche on the left had impressive propagation. Both likely failed on old snow buried Jan 4th. 

    Photo: Alex Drinkard

Avalanche Discussion

The story of the snowmobiler buried and killed in the Sierra Madre Range last Friday is important so I'll repeat it today in this zone forecast. This rider lost his life riding not in, but below avalanche terrain when is party triggered an avalanche while they rode carefully around rocks on relatively flat slope. While the avalanche only slid 300-400 feet vertically, it propagated almost 2100' across the slope. The set-up for this avalanche was not that different from the situation you could find in Togwotee, especially tomorrow. A slab of new snow sitting on a very weak layer, made worse by wind loading high on a ridgeline. There are many take-aways from the accident that will be available in a forth-coming report but several jump to mind.   

  • Route finding matters alot. When remote triggering is possible, which is the case whenever you have a deep and sensitive weak layer, give slopes a wide berth.
  • Rescue skills matter. Shovel and probe belong on your back, not your sled. This may not have changed the outcome in this incident, but seconds count. The victim, whose hand and feet were out of the snow, asphyxiated in 4-5 minutes.

Regioni coperte