Bollettino valanghe

Southeast Mountains

Crested Butte Avalanche Center
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Pericolo valanghe

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

Recent storms in March have greatly improved riding conditions, but those storms have also left avalanche problems in their wake. Normal caution will suffice for traveling in many areas. While in specific areas, heightened avalanche conditions exist for a new round of persistent slab avalanches. This avalanche problem has become possible to human trigger and would release in the upper snowpack. You can read about this avalanche problem below or in this recent blog post. 

Problemi valanghivi

  • Persistent Slabs

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

    A prolonged dry spell through the 2nd half of February and the beginning of March had left several persistent weak layers on the snow surface, that are now buried in the upper snowpack. The most concerning weak layers are two thin crusts with facets sandwiched between. This collapsible crust can most commonly be found on the eastern half of the compass. Where there is greater than a foot of snow on these crusts, persistent slab avalanches are possible to human trigger. In the SE Mountains, the most common areas to find enough snow on those crusts is on previously wind-loaded terrain, as highlighted by the problem rose above. Keep track of how deep these crusts are in the terrain you are riding, and make snowpack evaluations before stepping out into aggressive terrain.

    Persistent Slab Avalanches releasing on other aspects are notably less likely than the highlighted aspects above, and the avalanche problem is more isolated in the terrain. An example of one of those isolated areas could be the weak bed surface of an old avalanche that has been refilled with enough snow to form a new slab. Deep Slab Avalanches releasing on weak layers near the bottom of the snowpack have become very unlikely to human trigger. These deep slabs are expected to require a significant load such as a big cornice falling, or a big winter storm. 

    3/17/2021 view of the primary March layer of concern

Avalanche Discussion

Forecasters have been documenting a layer of concern in the upper snowpack for the last week. You can see some additional videos and imagins in the media gallery below, that follow this story line. It has taken the last week for enough snow to accumulate and create the new persistent slab avalanche problem. As highlighted in the avalanche problem description, not everywhere has accumulated enough snow for this problem. In the NW Mountains, the Irwin Area has accumulated the most snow, and I would expect similar conditions along the crest of the Ruby Range. An observation from last Monday, highlighted much less recent snow in Washington Gulch, compared to the Irwin Area. In those areas that have received less snow, this new avalanche problem is even more specific to previously wind-loaded terrain. Previously wind-loaded terrain is just what we are highlighting in the SE Mountains. It will be interesting to see just how reactive this March layer of concern becomes. Until there are stronger data points on one side or the other, it will be good to consider this potential avalanche problem in your terrain selection. There are a couple of other avalanche problems today that are expected to be small and fall under normal caution. On Cinnamon Mountain at 12,000ft, northerly winds are averaging in the 20mph range this morning. Those winds are strong enough to transport snow and form some small wind slabs at upper elevations. The high-temperature forecast for today doesn't get out of hand, but as the strong March sun makes its rounds today, we could see a couple of small loose wet avalanches shed off of steep sunny slopes. Wet avalanche concerns are expected to become more notable by Friday. The bellow treeline avalanche danger may increase to MODERATE as early as Thursday afternoon for wet avalanche concerns. 

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