Avalanche forecast

Eastside Region

Eastern Sierra Avalanche Center
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Avalanche danger

Thu
Alpine
4 · High
Treeline
4 · High
Below
3 · Considerable
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Highlights

Copious amounts of loose surface snow and strong winds will continue to create very dangerous avalanche conditions. Diverse and overlapping avalanche concerns will make it difficult to maintain adequate safety margins today and avalanches will be likely at all elevations. Traveling in or underneath avalanche terrain is not recommended.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Very Likely
    Size
    1–2.5

    Dangerous wind slab conditions exist on northerly and easterly terrain features. Strong winds will continue from the southwest today and you can expect continued slab development throughout the day. Particularly this afternoon as moderate snow showers return. Be suspect of terrain features that encourage drifting such as the leeward sides of ridgelines, gully features, and cross-loaded depressions.  Large natural and human-triggered avalanches are likely today and avalanches may run long distances, into lower angle, or treed terrain you may typically think of as “safe”. Be cognizant of what is above you today, travel in and below avalanche terrain is not recommended.

  • Storm Slabs

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

    As of the time of publishing, up to 34” of new snow has been recorded throughout the region with the highest totals in the northern part of the forecast area and in areas near the Sierra crest. Storm instabilities, both slabs and loose surface sluffs, will continue to be reactive today. Elevated caution is advised in steep unsupported terrain. 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.

  • Persistent Slabs

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

    Persistent weak layers in the upper snowpack were responsible for several human-triggered avalanches over the last week. Uncertainty around this problem is high but last night's rapid-loading event has added stress to this poor structure, and you can expect the sensitivity and distribution of this persistent slab problem to have increased substantially overnight. Managing this problem will require extensive evaluation and deliberate terrain choice. Remember that persistent slab avalanches often propagate across and beyond terrain features that would otherwise confine surface instabilities. Persistent slab avalanches can be remotely triggered from adjacent slopes. Give yourself a wide safety margin, be wary of hazards that may reside above you, and use terrain choice to limit your exposure.

    (3/24/2023)

    East Face of Tinemaha. Higher avalanche: large wind slab triggered by a rider booting a ridge. East aspect, 12,400 ft. Lower avalanche: persistent slab remotely triggered by the same rider. East-northeast aspect 9100 ft. Rider caught and carried ~1000 vertical feet in the second slide and came away with minor injuries.

    Photo: remotely-triggered

Avalanche Discussion

Extreme caution is advised if you decide to head into the backcountry today.  While the risk of natural activity was at its peak last night, it will remain likely for a human to trigger a large and destructive avalanche and you can expect rising hazards once again as snow showers return this afternoon. High levels of uncertainty exist around how this new load will affect the 3/19 interface. This weak layer has been productive and has been responsible for many recent avalanches and several close calls. Last night’s storm is the first major load added to this layer and it will be critical to give it time to adjust. Putting a wide berth between yourself and consequential terrain is the best way to manage high levels of uncertainty.

In addition to elevated avalanche concerns today there are also several objective hazards to consider. Deep loose surface snow will make for difficult travel conditions both on the road and in the backcountry. As yet another impactful storm clears today, considerate travel choices and strategic parking will be appreciated as crews continue to manage the extraordinary snow load this season. With good coverage at lower elevations this winter, recent avalanches have been running further, impacting roadways and buildings in the communities of Mammoth, Virginia lakes, Mono City, June Lake, and Aspendell. It is important to practice good run-out awareness. Triggering an avalanche above infrastructure could have devastating consequences.  Remember that it often takes multiple passes to clear roadways and trailhead parking. Road crews are working overtime to allow access to communities that have been stranded by heavy snow, avalanche activity, and flood damage. Blocking snow drifts, travel routes, and snow piles makes it impossible for road crews to continue their work.

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