Bollettino valanghe

Tetons

Bridger-Teton Avalanche Center
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Pericolo valanghe

Mon
Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
1 · Debole
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In sintesi

Triggering a small avalanche is most likely in areas where wind of varying direction has deposited snow into firm cohesive slabs. Although less likely, large avalanches are also possible on buried weak layers of snow. Areas of the most concern are characterized by steep, rocky, and wind affected terrain that contains a shallow snowpack.

Problemi valanghivi

  • Wind Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1–1.5

    Variable winds of 20 mph over the last few days have created wind slabs at the upper elevations that are up to 2 feet deep. Low density snow is still available for transport, even though the area hasn’t received new snow lately. Slabs could be both soft and hard. Northerly and westerly winds will continue to dominate the forecast, so southerly aspects have the highest probability of encountering wind slabs. 

    Monitor the wind direction and pay attention to signs of instability such as cracking within wind drifted snow.

    (1/21/2023) Wind slab cracking.

  • Deep Persistent Slabs

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

    The November 27 crust/facet combination is the layer of concern on West through East aspects at the middle and upper elevations. Areas with a shallower snowpack have been easier to trigger one of these large avalanches. Be cautious in steep, rocky areas with thin snow coverage where large portions of the snowpack are weak and faceted. Dig down or probe to determine if buried weak layers exist and pay attention to signs of instability such as audible collapsing of the snowpack.

    (1/16/2023)

    This avalanche was triggered on a west aspect off of Albright Peak around 10,000 feet.

    Photo: C. Martin

Avalanche Discussion

As you may have noticed, yesterday we transitioned from a Persistent Slab to a Deep Persistent Slab problem in the Tetons and Greys Forecast Areas. This debate seems to always be a challenging one for anyone in the avalanche world. The simple reason for this transition is when weak layers of snow are buried roughly over a meter deep. For most areas in the Tetons and Greys, we’ve hit this threshold. But the other important reason has to do with the unpredictable nature of these types of avalanches. As weak layers become buried deeper and deeper they become more and more difficult to trigger. Couple this with a snowpack of varying depth and sensitivity to triggering and this problem becomes even more difficult to predict. Simply put, the deep persistent slab problem is a way for us to characterize this unpredictability. The best way to reduce uncertainty is avoiding those thin, shallow areas with weaker layers where we have found unstable results in pits and actual avalanches. 

Northwest flow with little to no new snow will continue to dominate the area. These deep persistent slabs may seem dormant during these periods. Think about that low probability, high consequence scenario and pay close attention to large loading events of snowfall which could tip the scale to triggering these deep slabs. 

Regioni coperte