Lawinenlagebericht

Togwotee Pass

Bridger-Teton Avalanche Center
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Lawinengefahr

Thu
Hochgebirge
2 · Mässig
Waldgrenze
2 · Mässig
Unterhalb
Keine Stufe
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Veraltet — dieser Lagebericht ist 2 years ago abgelaufen. Du siehst vergangene Verhältnisse, nicht den aktuellen Bericht.

Kernpunkte

Weak layers at the base of the snowpack can still be triggered by a passing skier or rider. Choose terrain carefully as these avalanches are most likely to be triggered over thin spots in the snowpack in rocky and wind affected terrain. Avalanches are unlikely below 9,000. 

Lawinenprobleme

  • Wind Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    1–2

    Winds ramped up yesterday and will continue to be strong enough today to build more wind slabs. These new wind slabs could be up to a foot thick and will be  sensitive to triggering due to the weak surface facets that they formed upon.  If triggered, they will also further stress deeper weak layers in the snow as the debris moves downhill. Be on the look out for obvious signs of wind slab like drifts, pillows and cornices. A small avalanche could trigger a larger and more dangerous persistent slab avalanche involving the entire seasons snowpack. Wind was primarily out of the southwest in the past 24 hours but will veer to the northwest today. 

  • Persistent Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    1–2

    Togwottee Pass is especially very cold and dry most winters making the area an excellent example of a continental snow regime. Snow left out in the cold turns into the loose, sugary crystals earlier in the season that you can now find almost anywhere you dig. There are two strategies typically used to reduce your chance of triggering an avalanche. The first relies on careful route finding to avoid steep, rocky areas,  slopes  over 30 degrees that are convex, especially those that are unsupported from below an any other terrain that shows signs of wind affect such as drifting, nearby cornices or textured surfaces where the wind has stripped away surface snow. The second strategy is to rely on luck and ride wherever you feel like riding. That strategy will only take you so far and is not advisable. As snowfall and significant wind-loading recede into the past, the odds of triggering an avalanche diminish, but only by a little. Remember that a danger rating of 2 out of 4/5 are not great odds. 

    An example of terrain where persistent slab avalanches are most likely.

Avalanche Discussion

As Gabrielle wrote yesterday, other areas like the Tetons and lower elevations in other zones are becoming more stable with low avalanche danger. Togwotee remains unstable with an elevated danger rating. Here's why:

  1. The weak layers are proven. Avalanches failed on weak layers near the surface and at the ground during any change in weather conditions.  
  2. The weak layers are ugly. Sugary facets remain weak and consistently produce unstable snowpack test scores.  
  3. The weak layers are well distributed. Due to the higher elevation, older snow from earlier in the season is located in more terrain than in neighboring zones. 
  4. More trigger points exist. This zone has seen enough snow to build a slab over time that buries weaker snow deeply, but not enough to completely armor the weak layer from the impact of our weight. 

Want to learn more about how triggering a persistent slab avalanche from a thin spot works? Check out this sweet video made by a seasoned avalanche professional.

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