Avalanche forecast

Eastside Region

Eastern Sierra Avalanche Center
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Avalanche danger

Fri
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
2 · Moderate
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Highlights

There is a lingering chance for human-triggered avalanches failing on shallow buried weak layers from late March. With increased temperatures today wet snow instability is possible on solar slopes at lower elevations. Continue to exercise caution as the upper snowpack makes its transition from winter to spring.

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1.5–3

    Cold clear nights in the short windows between storms at the end of March created thin melt-freeze crusts and weak layers of near-surface facets at various depths within the upper snowpack. While these avalanches are possible in isolated areas, we are seeing a decrease in signs of instability. Feedback may be limited and, if triggered, avalanches could fail suddenly and in surprising ways. Remember that persistent slab avalanches can propagate across and beyond terrain features that would otherwise confine surface instabilities and can be remotely triggered from below or adjacent to steep slopes. You can manage uncertainty by reducing exposure and maintaining good terrain margins. Use extra caution around convexities and wind-drifted slopes near treeline. 

    (3/30/2023)

    Remotely-triggered avalanche on Punta Bardini 3/29/23

  • Loose Wet

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–2

    An increase in temperatures today combined with light winds and clearing skies means that wet snow instability is possible on sunny low-elevation slopes. Look out for progressively wetter surface snow on sunny aspects. Rollerballs and pinwheels are the most common signs that the likelihood of wet snow instability is increasing. If these signs are present then it may be a good idea to adjust route selection to avoid passing underneath steep sun-baked slopes, especially in confined or cliffy terrain that limits options to escape runouts and could concentrate debris flows.

    (4/1/2023)

    Small wet loose avalanche that ran above Mono Lake on 4/1/23

Avalanche Discussion

Uncertainty in today's forecast surrounds the sensitivity and distribution of the persistent slab problem. During this week's mild weather, these layers have likely gained strength, but the isolated nature of the problem means that it has been difficult to track and measure improvement in stability. Melt-freeze metamorphism in the surface snow below treeline, and wind scouring above treeline have made the problem even more isolated. Despite these positive trends the 3/19 layer can still be found within the top meter of the snowpack and continues to show potential for human-triggering in stability tests.

The last confirmed avalanche on the 3/19 and 3/29 near-surface facet layers was reported on 3/31 - a week ago. However, avalanches that released during the wind event on 4/2 and 4/3 propagated long distances and remote triggers suggest these avalanches may have involved buried persistent weak layers.

Warming will be a factor today and wet loose activity may provide a larger trigger for weaknesses in the upper snowpack. Use caution around slopes that are becoming wet as the winter snowpack begins its transition.

As a final note: Pockets of wind slab deposited by the most recent wind event may still be found on southerly slopes above treeline. These small isolated slabs will be most concerning in extreme or consequential terrain.

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