Bollettino valanghe

Sawtooth & Western Smoky Mtns

Sawtooth Avalanche Center
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Pericolo valanghe

Fri
Alta quota
3 · Marcato
Limite del bosco
3 · Marcato
Sotto il limite
2 · Moderato
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Non aggiornato — questo bollettino è scaduto 3 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

Conditions are dangerous. You could trigger large avalanches involving weak snow near the ground. These are most likely at upper elevations and on middle elevation slopes facing away from the sun. You could trigger slides from gentler terrain below, above, and to the sides of steep slopes. 

Problemi valanghivi

  • Persistent Slabs

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

    You could trigger 2-3 foot thick avalanches that fail on buried persistent weak layers—sugary facets or crust + facet combinations—near the bottom of the snowpack. Assume these old, weak layers of snow exist on all upper elevation slopes and on middle elevation slopes facing the northern half of the compass (W-NW-N-NE-E aspects).

    In the past week, every observation we've received noted some form of snowpack cracking or collapsing (observations). These are clear indicators that the snow you're traveling on is unstable. The only surefire way to avoid this problem is to steer clear of steep slopes where these old facets exist. Sunshine melted the early season snow on many SW-S-SE-facing slopes, but it's easy to unknowingly wrap around to shadier slopes where this weak layer exists. You can verify the presence of this layer by digging a quick hole. The weak facets will appear grey and feel loose and crumbly (photo).

     

Avalanche Discussion

Your odds of triggering an avalanche are slowly decreasing, but each day is only incrementally safer than the last. Benign weather, without additional snow or wind-loading, will help slopes stabilize, but the process is slow. The good news is that our persistent slab problem is fairly well-defined (see description above).

Yesterday, in the Headwaters of the Salmon, Ben and I experienced nearly continuous snowpack collapsing (observation). A few large booming collapses traveled far across the slope, stopping only due to breaks in the terrain. The snowpack structure is ugly, and the ubiquitous cracking and collapsing of the snowpack are signs that many slopes remain unstable. 

The downside to a relatively well-defined problem is our tendency to assume we can nibble at the edges. As fair weather continues, it will be easy to get complacent, unintentionally reducing our margins of safety. For now, I have no reason to believe that hopping into a steep N-facing bowl with this problem would do anything other than produce an avalanche. 

As conditions improve, the frequency and spatial extent of collapses will decrease. While a good sign, it represents only one small step in the right direction. Where this problem exists, there is no switch to flip or a single piece of evidence indicating a slope is safe. Entering avalanche terrain is an odds game and the only way to significantly reduce our chance of triggering an avalanche is by sticking to slopes without weak snow near the ground. 

Regioni coperte