Boletín de aludes

Eastside Region

Eastern Sierra Avalanche Center
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Peligro de aludes

Fri
Alta montaña
3 · Notable
Límite del bosque
2 · Moderado
Bajo el límite
2 · Moderado
Desactualizado: este boletín caducó 5 years ago. Estás viendo condiciones pasadas, no el boletín vigente.

Lo esencial

CONSIDERABLE avalanche danger persists at upper elevations while MODERATE avalanche danger exists at lower and mid-elevations. Human-triggered avalanches remain LIKELY today. Fresh and sizable wind slabs are our main concern; however, storm instabilities such as loose dry and storm slab avalanches will also be possible in sheltered and steep terrain Careful snowpack evaluation, cautious route-finding, and conservative decision making are essential.

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Problemas de aludes

  • Wind Slabs

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

    Expect to find wind slabs ranging insensitivity on northerly and easterly terrain near aspects above treeline today. Winds have already shifted to the north and speeds are expected to be light for most of the day. We may see a slight increase in speeds this afternoon into the moderate range however we do not expect to see significant new slab development. Be on the lookout for fresh slab development on more southerly aspects above treeline if the winds out-perform the forecast.  Surface facets and a variety of hard and slick crust layers from before this last storm may exasperate the avalanche problem making things more sensitive.  Be suspect of terrain features that encourage drifting such as the leeward sides of ridgelines, gully features, and cross-loaded depressions. Blowing snow, recent cornice growth, drifting, stiff hollow feeling upside-down snow, and textured, uneven snow surfaces are all signs of recent wind transport. Use these clues to identify and avoid areas with recent wind deposits. 

  • Loose Dry

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

    Field reports from yesterday found our recent storm snow to be largely right-side-up and unconsolidated. In addition, multiple natural and human-triggered loose dry avalanche s were reported. While we expect this surface snow to stabilize relatively quickly loose dry avalanches may still be possible today, particularly on steep slopes in sheltered terrain. Convex rollovers and slopes over 35° in steepness are potential problem areas. When in doubt, avoid being on or underneath avalanche terrain and be cognizant of your exposure to terrain features that increase the consequences of avalanches. This includes road cuts, gully features, cliff bands, and mid-slope depressions.

  • Storm Slabs

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

    Field reposts yesterday described conditions more conducive to loose dry activity (right-side up and unconsolidated), however, as this recent storm snow begins to settle and consolidate storm slab avalanches remain possible in sheltered areas at mid and lower elevations. Exasperating this problem is the old snow surface, made up largely of near-surface facets, shallow melt-freeze crusts, slick wind board, or a combination of the three.  Do your own localized assessments as you travel in the backcountry today. Steep, unsupported slopes and convex rollovers are potential problem areas particularly in areas around Mammoth that received more significant snowfall totals.  

Avalanche Discussion

There is a common saying that has significance to our current snowpack “today’s surface is tomorrow's weak layer”.  Our most recent run of spring-like weather left us with a highly variable surface prior to this most recent storm, one made primarily of hard crusts and loose surface facets. While clear skies and cold nights helped maintain decent ski quality through our long dry spell in the form of “recycled powder” on more shaded slopes, this combination of shallow crusts, and loose faceted snow is now the base of our more recent snowfall. It will be prudent for the backcountry traveler to keep this potential weak layer top of mind. Particularly as our new snow begins to consolidate into a more substantial slab. Facets are always suspect when they can be found below the surface. Continue to use safe travel techniques and keep in mind that while we cannot control the snowpack we can control our terrain choice. When uncertainty is high,  keep it simple and choose less consequential terrain.

Recent Observations

-3/10- June Lake BC- New snow, Surface instabilities, and Natural activity in the Negatives

-3/10- Mammoth Area- New snow, loose dry activity, buried near-surface facets

-3/10- Mammoth Area-  snowpack observation from the Lakes basin

-3/10- Mammoth Area- Snowpack structure, wind effects on Panorama dome

-3/10-Rock creek Area- small amounts of new snow

-3/9- Mammoth Area- Dust on crust, small loose dry avalanche activity, and strong winds in the Sherwins

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