Boletín de aludes

Tetons

Bridger-Teton Avalanche Center
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Peligro de aludes

Mon
Alta montaña
3 · Notable
Límite del bosque
2 · Moderado
Bajo el límite
1 · Débil
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Desactualizado: este boletín caducó 3 years ago. Estás viendo condiciones pasadas, no el boletín vigente.

Lo esencial

It will be possible to trigger an avalanche 2-4 feet deep in steep wind loaded terrain at the upper elevations. Careful assessment of the snowpack will be critical in avoiding avalanches. Sticking to lower angle slopes while the most recent load continues to adjust will be essential today.

Problemas de aludes

  • Persistent Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Possible
    Tamaño
    1–2

    Snowfall over the last week has created slabs 2-4 feet thick. The recently formed slabs are sitting on weak snow in the upper elevations. These slabs have proven themselves to be most reactive in steep, wind loaded terrain on the north half of the compass. While instability on this interface peaked 3-4 days ago during a natural avalanche cycle, human triggered avalanches continue to be reported. Yesterday, three large avalanches involving this interface were remotely triggered by skiers in steep, wind affected, and unsupported terrain at the upper elevations. These avalanches indicate that the snowpack is still adjusting to the most recent load in some locations.

    Approach steep terrain in the upper elevations with suspicion. Extra caution is advised in exposed, wind affected terrain that is punctuated by rocks and cliffs. Be on the lookout for obvious signs of instability such as collapsing and shooting cracks. When these signs are present it is time to back off and choose simpler terrain. It is important to make your own stability assessment of a particular slope before committing to any terrain capable of producing an avalanche.

    A widely propagating avalanche that was remotely triggered yesterday (2/10) in Grand Teton National Park.

  • Deep Persistent Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Possible
    Tamaño
    2–3

    Weak snow that formed during a prolonged dry period in December remains a lingering threat. Reactivity on this layer is approaching a dormant phase, but is not there yet. Last week’s storm brought a significant load to the mountains and stressed this weak interface. Very large avalanches involving weak snow from December are most likely to occur when an avalanche breaking in the newest snow “steps down” to the January 4th weak layer. This scenario occurred yesterday on the north face of Rendezvous Mountain. If triggered, these avalanches could break 3-5 feet deep and would be unsurvivable if one were to get caught, carried, and buried.

    A large avalanche that was remotely triggered yesterday (2/10) on the north face of Rendezvous Mountain. The avalanche below the cliff band was triggered when it was impacted by the upper slide and stepped down to weak layers deeper in the snowpack.

Avalanche Discussion

Spatial variability is a term that avalanche professionals like to use frequently. When talking about avalanches, it often means that stability can vary significantly in a small geographic area due to subtle changes in aspect, elevation, slope angle, and snow depth. This describes the current avalanche problem nicely. Last week’s storm brought a significant load to the mountains in a short period of time (2.5-4” SWE). In some locations, such as sheltered/sunny aspects, the new snow is bonding well to the old snow surface. In other spots, namely shady/wind affected terrain, the snowpack is taking longer to adjust. Recent remotely triggered avalanches are evidence of this. Variability in stability means that it is important to make your own assessment of the snowpack before committing to steep terrain. Digging down to the most recent interface can be helpful, but also noting the characteristics of the terrain where you are riding is important. Red flags include the following.

  • Windy. Is there evidence of wind loading? Does the terrain seem exposed to wind?
  • Steep. Is the terrain above 35 deg? Does it roll over?
  • Shaded. Nearly all of the recent avalanches have occurred on slopes with a northern tilt.
  • Rocky. Again, many of the recent avalanches have occurred in areas that are rocky or above cliff bands.

The interface that was buried on 2/2 was created by a week of warm, relatively dry weather. As a result, it is not terribly weak. The snowpack simply needs more time to adjust and stabilize. Continued vigilance and conservative terrain choices are recommended over the next few days.

Regiones cubiertas