Avalanche forecast

Eastside Region

Eastern Sierra Avalanche Center
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Avalanche danger

Tue
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
2 · Moderate
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Highlights

Slabs of drifted snow may be sensitive to human triggers in leeward terrain. Buried weak layers have been challenging to assess. They have caused some avalanches to break widely and caught people off guard. You can hedge your bets against unwanted surprises by giving yourself a wider margin for error and having options that include simple, sheltered terrain with low slope angles.

Avalanche problems

  • Wind Slabs

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

    Cold temperatures may slow the bonding process, keeping recently drifted slabs sensitive this morning. As winds increase across the region from north to south this afternoon, fresh drifts could develop in leeward terrain. Specific features of concern include steep slopes below ridgelines, the sidewalls of gullies, and cross-loaded depressions. Recent avalanche activity, cracking within the surface snow, blowing snow, and hollow upside-down feeling snow, are all clues that wind slabs may be unstable in your area. If triggered, avalanches could propagate widely, breaking above or around your skis, board, or machine. Sheltered terrain with lower slope angles may hold softer snow and safer riding.

    (3/26/2023)

    Intentionally triggered wind slab near treeline in the Mammoth Area

  • Persistent Slabs

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

    In isolated areas, a reactive combination of facets and surface hoar atop a crust is buried up to two and a half feet deep under snow from the past week's storms. Yesterday, forecasters got propagating test results in Mammoth. Shooting cracks and collapses were reported on this layer in the Bishop area on Saturday. It has also been the prime suspect in several natural and human-triggered avalanches from south of the forecast zone, the Sherwins, and the June backcountry over the past week. Use caution in areas that had firm snow surfaces before the March 19th storm. Track weaker snow throughout your day by digging and probing. Signs of instability include shooting cracks, collapsing, and remotely-triggered avalanches. That feedback may not be consistent and avalanches have caught people by surprise. Be careful around wind-loaded terrain and convexities. You can build a wider safety margin into your tour plan to limit your exposure to a problem that is difficult to assess.

Avalanche Discussion

Strong west winds transported snow on Sunday morning creating fresh, sensitive drifts in some areas. Forecasters found small wind slabs reactive on leeward terrain features near treeline in Mammoth. Several professional reports from near and above treeline in June found no signs of instability. A rider was caught and carried 1300 feet in a large avalanche triggered on a southeast aspect at 10,500 feet on Mono Jim Peak yesterday. Luckily there were no injuries. It is unclear whether this avalanche failed on a weak layer buried earlier this month, which adds some uncertainty to the distribution of the persistent slab problem above treeline. 

Today will be the last day with strong spring sun and warming temperatures. We do not expect areas of deep wet snow to be widespread. But if you see rollerballs from very steep slopes in the afternoon, you can avoid the odd wet loose avalanche by moving to shady terrain. That won't be a problem as more snow and cold weather move into the region.

As another impactful storm approaches, 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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