Avalanche forecast

Eastside Region

Eastern Sierra Avalanche Center
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Avalanche danger

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

Avalanche danger elevates to MODERATE today.  The primary concern is for Wind Slab on E-SE-S-W aspects. The main drivers of this increasing hazard are a dramatic shift to much warmer temperatures and a clear sunny day that may destabilize new snow (8-12”) at higher elevations localized around Mammoth Lakes.

Avalanche problems

  • Wind Slabs

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

    Although a majority of the forecast zone only received trace to minimal amounts of new snow the past few days, the Mammoth Lakes area saw some significant accumulation of 8-12” above 9000ft near the Mammoth Crest and likely San Joaquin Ridge to the north.  This new snow fell under frigid temperatures (0degF-single digits) with winds that ranged from extreme SW to a more northerly pattern the past 2 days. The MAIN CONCERN today is the dramatic shift from previous icy temperatures and overcast cloudy skies to a clear sunny day with significant warming. The combined effects of settlement, winds, and input of solar radiation with warming temperatures may cause slabs to become sensitive and reactive to skier trigger. Keep in mind that this new snow fell on a variety of old snow surfaces which ranged from very firm to loose and faceted. Primary aspects to be aware of are those that receive the most sun (E-SE-S-W) for solar induced instability. Northerly aspects additionally should also be taken into consideration for wind slab that developed with the dynamic alpine winds yesterday. Terrain adjacent to ridgeline, gullies, unsupported slopes, and convex rolls should be looked at with a critical eye.

Avalanche Discussion

Most of the forecast zone received 1-2” of new snow with this storm, but the Mammoth Crest exceeded expectations with 8-12” in some areas. With limited weather instrumentation, it would be no surprise if other areas in the alpine, particularly in the northern part of the forecast zone received more snow than we are aware of. This uncertainty of local snow totals combined with the abrupt shift to warmer tempeartures prompted the forecast team to elevate the avalanche hazard. It has been a long drought with no snow and there could be some dynamic conditions out there today. Time to be heads up, especially where terrain is getting heated within sheltered and sunny conditions. One place that comes to mind is the “Red Cone approach” where convex easterly facing rolls reside over commonly used skin tracks and associated terrain traps and gully features.

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