Boletín de aludes

Silver Valley & Bitterroot Mountains

Idaho Panhandle Avalanche Center
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Peligro de aludes

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

Lo esencial

New snow, rain and variable winds over the past weekend have created new slabs on many slopes. The recent snowfall was heavier and denser than previous storms, making avalanches easier to trigger, particularly on slopes where drifted slabs are firmer. The most likely spots to trigger avalanches are at the margins of these firm, wind-deposited slabs. For the safest travel, stay off of steeper wind-loaded slopes and choose sheltered areas where the snow surface isn't textured by the wind.

Problemas de aludes

  • Storm Slabs

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

    Snow totals from last weekend ranged from 4 to 7 inches in the Bitterroot Mountains and Silver Valley. The latest snowfall arrived with warmer air compared to previous storms, initially pushing the rain line to around 6,500 feet before transitioning to wet, heavy snow. The presence of a slippery sliding surface underneath may make these shallow slabs more reactive, with the potential to break wider than expected, especially where drifting is slightly deeper.

    Pay attention to the slope’s aspect, watch for fresh cornice growth, and anticipate problematic drifts in areas you may not typically see them, due to variable winds. Use caution on slopes around 35 degrees if you notice a transition from soft to stiff snow or see blowing snow along ridgelines.

    Triggering a smaller slide above a cliff or terrain trap could have serious consequences if you don’t have an exit strategy

    Photo: Izzy Davis

  • Persistent Slabs

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

    Faceted grains persist underneath a couple of older rain crusts two to three feet deep across our forecast zones. The overlying slab has stiffened significantly in the last week and makes impacting these weaker grains more difficult. Where the crust has degraded and is more breakable, the facets are overall larger and weaker. Your chances to trigger one of these lower-probability, higher-consequence slides increase near exposed rocks or wind-scored areas of slopes where these weak snow grains may be closer to the surface.

    Persistent slab avalanches can behave unpredictably and span across adjacent terrain features. Choose slopes free of surface obstacles or terrain traps just in case something goes wrong. Default to lower-angled slopes if your snowpack assessments are inconclusive around the sensitivity of faceted crusts.

    (12/31/2024)

    The December 18 rain crust is thin, breakable, and very translucent. It lurks around two feet deep and was stubborn in our snowpack tests. We did observe resistent planar failures with moderate force. Selkirk Mountains. December 31, 2024.

    Photo: Chris Bilbrey

Avalanche Discussion

The weekend's snow totals have been slightly less than initially forecasted. Nevertheless, all mountain regions received enough new snow to refresh surface conditions, though not enough to significantly increase avalanche danger. While hazards are still present, the most concerning risks are likely confined to the new storm snow. As you travel across different aspects and elevations, monitor how much new snow has accumulated. The latest storm brought a variety of wind directions, so anticipate more cohesive slab formation on slopes that usually have shallower slabs or are typically wind-scoured.

The key question before committing to steeper slopes is whether a shallow avalanche you trigger will remain confined to the recent storm snow or break deeper into a faceted crust. As time passes since the last significant loading event, this step-down scenario becomes less likely. However, it remains uncertain how close the grains are to the "reactive" edge. This uncertainty can be managed by making conservative terrain choices. Avoid likely trigger spots and refrain from lingering below a slope while others ascend or descend. Have a solid exit plan, expose only one person to a slope at a time, and be aware that deeper avalanches may fail without warning.

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