Boletín de aludes

Northwest Mountains

Crested Butte Avalanche Center
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Peligro de aludes

Tue
Alta montaña
3 · Notable
Límite del bosque
2 · Moderado
Bajo el límite
2 · Moderado
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Desactualizado: este boletín caducó last year. Estás viendo condiciones pasadas, no el boletín vigente.

Lo esencial

Gusty winds drifting snow at upper elevations could produce an isolated natural avalanche on leeward terrain.  Some slopes on the north half of the compass remain sensitive to human triggers like these avalanches from Sunday (Elkton, Schuylkill Ridge).  Careful snowpack evaluation and conservative terrain selection will help reduce your avalanche risk on northerly-facing terrain.  Wind-sheltered southerly slopes are less likely to produce slab avalanches.  

Problemas de aludes

  • Persistent Slabs

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

    The latest human-triggered slab avalanches failed on small facets below the recent storm snow. These avalanches have primarily released on northerly facing slopes, with average crown heights ranging from 1 to 2.5ft. Persistent slab avalanches can also release in weak layers in the middle or at the bottom of the snowpack, becoming very large and destructive. The newest generation of persistent slabs can be managed with slope angle choices and snowpack evaluation.  The deeper and older persistent slabs would most likely be triggered from areas where the snowpack thins near trigger points. Natural avalanche activity will continue to be possible on slopes with active wind loading.  

    This notable natural avalanche ran Friday night or early Saturday morning. The avalanche debris pushed into the valley below. Schuylkill Ridge.

  • Wind Slabs

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

    Westerly winds have built thick slabs on the lee sides of terrain features over the last few days.  Slabs can release within the recent storm snow or step down into deeper weak layers where they overlap with the persistent slab avalanche problem.  Sunday evening and night winds shifted to the southwest and may find more snow to drift.  Fresh drifts are most likely found beneath cornices, below ridgetops, and cross-loaded into gullies.  Avoid terrain where you encounter signs of recent or active drifting.  Above treeline terrain will commonly have the most drifting, but you could encounter drifts at lower elevations closer to treeline.

    This small wind slab was human-triggered on Coney's yesterday. 

Avalanche Discussion

Snowfall totals from Thursday night through Sunday morning varied widely across the forecast zone.  In the Northwest Mountains, settled storm totals range from about 1 to 3 feet.  In the Southeast Mountains, totals are closer to a foot or less.  This difference in storm totals creates a notable difference in avalanche problems.

Northwest Mountains:  Over the past few days, most avalanche activity has occurred directly beneath the recent storm snow on a layer of faceted grains.  On Sunday, avalanches were triggered near Elkton and Schuylkill Ridge 1 to 2 feet deep.  This interface is the most likely place to trigger an avalanche.  You can encounter this issue on the north half of the compass in both drifted and sheltered terrain.  Assessing the snowpack to determine the likelihood of an avalanche can be challenging and lead to unpredictable results.  A simple solution is to select more conservative slope angles and smaller terrain features free from terrain traps.  A smaller chance exists for avalanches to break deeper in the snowpack like this natural avalanche from Friday night or Saturday morning on Schuylkill Ridge near Pittsburg.  Southerly-facing slopes have less problematic structures, but caution should be used around drifted features at upper elevations.

Southeast Mountains:  With notably less snowfall, new avalanche problems are largely patterned by recent drifting.  Although new avalanche problems are the most likely to be triggered, weak layers deeper in the snowpack are capable of avalanching.  Zach's observation from Cement Creek/Star Pass last week sheds more light on the potential to trigger an avalanche on old, weak layers in the middle or bottom of the snowpack.  Use caution if you travel near northerly-facing slopes with signs of recent drifting, as an avalanche that breaks in a recent drift could step down to deeper layers.

Cloud cover and gusty winds will likely keep snow surfaces cool on Monday.  The Wet Loose avalanche problem was removed from the problem list today, given the weather forecast.   However, air temperatures warm from previous days and could wet the snow surface on isolated sunny slopes, particularly if there's more sunshine than expected.

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