Boletín de aludes

Northwest Mountains

Crested Butte Avalanche Center
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Peligro de aludes

Fri
Alta montaña
3 · Notable
Límite del bosque
3 · Notable
Bajo el límite
3 · Notable
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Desactualizado: este boletín caducó 4 years ago. Estás viendo condiciones pasadas, no el boletín vigente.

Lo esencial

Impressive southwest winds and up to two feet of snowfall are creating dangerous conditions.  Drifted slopes at upper elevations are the most dangerous places although yesterday's extreme winds drifted snow at lower elevations as well.  Avoid drifted terrain and use caution in sheltered locations by observing the bonding between the new and old snow.  Shooting cracks and collapses are clear signs of unstable conditions.  Natural avalanche activity is possible where wind-loading occurs. 

Problemas de aludes

  • Storm Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Likely
    Tamaño
    1.5–2

    Storm slabs will be likely to human triggers or they may release naturally on wind-loaded terrain; simply avoid wind-drifted slopes.  In wind-sheltered terrain, there is uncertainty as to how reactive this avalanche problem will be. While in wind-sheltered areas look for small, steep test slopes to help identify how reactive Storm Slabs are in the area you are traveling.  

    2/22: A skier-triggered Storm Slab broke at the base of the recent storm snow on a sheltered northeast-facing slope.  This is good evidence that even sheltered terrain can produce dangerous human-triggered avalanches. 

  • Persistent Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Possible
    Tamaño
    2–2.5

    Since the end of January, the upper snowpack has become layered and more complicated. Persistent slab avalanche concerns will first develop in the highlighted areas above. Buried in the upper snowpack in these highlighted areas, is a stack of thin crusts with layers of facets between them. These persistent weak layers may produce remotely triggered avalanches, and avalanches that both release deeper and wider than you expect. Given how specifically located this avalanche problem is, changing avalanche conditions could easily catch you off guard while moving from one slope to another.  Uncertainty exists as to when and how much loading it will take before crust/facet layers in the upper snowpack begin to fail.  Collapsing, or whumpf-ing, are a clear sign that these layers have reached their breaking point and you should avoid traveling on or below steep slopes.

    Layers of facets sandwiched between thin crusts are creating persistent slab avalanche concerns in some areas. 

Avalanche Discussion

Mother nature delivered up to 2 feet of snow in the Northwest Mountains and around a foot of snow in the Southeast Mountains accompanied by strong to extreme southwest winds.  The meteorological evidence and human-triggered avalanches from Wednesday (Schuylkill Ridge, Climax Chutes) clearly point to dangerous avalanche conditions on drifted terrain.  More snowfall and southwest winds today will keep the pressure on drifted terrain and add more fuel to the dangerous conditions.  Drifted slopes in the Southeast Mountains have the distinct possibility of breaking in old snow deeper in the snowpack and becoming larger and wider than expected.    Given the strength of recent winds, do not be surprised to find some drifted terrain features below treeline. 

Sheltered terrain presents some uncertainty.  Storm totals in the Northwest Mountains are deep enough to be dangerous in sheltered areas and less dangerous in the Southeast Mountains as storm totals are roughly half.  Take the time to look for signs of instability, test the bonding between the old/new snow interface to better understand how it is bonding.  This avalanche in a sheltered location on Schuylkill Ridge is a good example of the potential poor bonding between the storm snow and the old surface or this observation of shooting cracks on Snodgrass.

The upper snowpack on easterly and westerly slopes contains several facet/crust layers that could become reactive during this stormy period.  A test profile from an easterly slope on Schuylkill Ridge did not look to have enough recent storm snow to cause an issue, but areas with more snow from drifting may be getting closer like this surprise remotely-triggered avalanche from Mount Emmons immediately before the storm.  Collapsing is a clear sign those crusts have reached a tipping point.  You can quickly dig down and test these layers of concern as they are only a few feet below the surface.

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