Avalanche forecast

Eastside Region

Eastern Sierra Avalanche Center
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Avalanche danger

Sat
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
3 · Considerable
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Highlights

10” of new snowfall yesterday combined with extreme SW winds created fresh Wind Slabs at all elevations on northerly to easterly facing terrain.  This new snow combined with 30-40” of snow earlier this week is lying on top of a weak sugary underlying snowpack in many areas, leading to possible Persistent Slab Avalanches.  Avalanche danger is CONSIDERABLE at all elevations do to the likelihood and potential size of a human triggered avalanche.

Avalanche problems

  • Wind Slabs

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

    About 10” of new snow fell yesterday morning, with strong southwest winds cranking up to 80mph at low elevations, and 110mph over high ridgetops.  Virtually nowhere was wind protected yesterday, not even low elevation trees.  Winds died off dramatically in the evening and were light out of the north overnight, and should remain light to calm thru today. Watch for areas of dense wind deposited snow today that could still be sensitive to human trigger on northerly thru easterly facing terrain, especially below ridges, sidewalls of gullies, and cross slope catchment areas.  These may be found lower down on the slope than expected given the ferocity of yesterday’s winds. The fact that these wind slabs will be on a healing trend throughout today means that they will become more and more stubborn to trigger, and that if they break it will most likely be above you.  Give them extra respect for at least another day.     

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    2–3

    Layers of weak sugary faceted snow from early season storms in October and November have been found on east to north to west facing terrain above about 9,200ft. This weak snowpack just had a massive load added on top, with 30-40” of snow from Monday-Tuesday, and an additional 10” Wednesday night thru mid-day Thursday, and MUCH more where the snow was wind-deposited. Many avalanches failed on these weak layers during the big loading event, and at least one confirmed report came in of a slope avalanching, filling back in, and avalanching again on the same weak layers near the base of the snowpack. The snowpack will adjust, making these weak layers less and less likely to be triggered, but this process takes some time.  For now, steep slopes with old snow underneath are a scary prospect, and venturing out on them could be a roll of the dice. Triggering a deep persistent weak layer would likely result in a very large and deadly avalanche. Play it safe by avoiding this problem by sticking to lower angle slopes, slopes below ~9,200ft, or more southerly to westerly facing terrain at higher elevations. 

Avalanche Discussion

Persistent slab problems are the trickiest to deal with.  What you can see on the surface won’t tell you much, unless you get an obvious woomph or shooting crack, which you might not get until you are on a steep slope with an avalanche breaking around you. You could get away with travelling on the majority of a suspect slope, until someone hits a point just shallow enough that triggers a deep failure that propagates into a huge slope-wide avalanche. Do your own localized investigations with your shovel in safe terrain, and let others know what you find through our Observations Page. 

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