Avalanche forecast

Central Sierra Nevada

Sierra Avalanche Center
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Avalanche danger

Thu
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
2 · Moderate
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Highlights

Increasing winds today will form wind drifted snow with potential wind slab avalanches in exposed areas.  Storm slab avalanches remain a concern with the recent snow we received yesterday in wind protected areas.  Use caution on steep wind loaded slopes and any areas that show signs of unstable snow. 

Avalanche problems

  • Wind Slabs

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

    Winds shifted to the NE late yesterday afternoon and have been blowing 20 to 35mph over the Sierra Crest overnight.  These winds are expected to continue today and increase with gusts up to 45 to 55mph this afternoon.   These winds will have 1 to 2 feet of light low density storm snow to transport throughout the day creating new wind slabs on SE-S-SW-W-NW aspects in near and above treeline areas.  Areas that receive the highest wind speeds could scour all the recent snow off of N-NE-E aspects back down to pre-storm firm crusts.

    Look for blowing snow, new cornice formation, wind drifts, and snow surface scouring as clues to where wind slabs are forming.  Snow surface cracking in wind drifted areas or denser snow over lighter snow are signs that wind slabs are forming and might be unstable. 

  • Storm Slabs

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

    Recent storm snow totals are in the 1 to 2 foot range throughout the forecast region.  This new snow sits on a variety of old snow surfaces that could present bonding issues as well as some weaknesses within the recent storm snow itself.  Cold temperatures will slow down settlement rates preserving some of these storm snow instabilities for a longer period of time.  Near surface facets exist in some wind protected near and below treeline areas on NW-N-NE aspects and remain weak in some locations.  As this storm snow gains strength and shows more slab like characteristics, avalanche activity may become possible on this weak layer.

    With some unknowns about these storm slabs, caution is advised.  Look for cracking in the snow, around skis, or while traveling through terrain.  Signs of cohesion of the recent storm snow could indicate storm slabs still exist and may present issues.  Any collapses or whumpfing sounds will indicate that previous weak layers are being overloaded by you and the new snow.    

Avalanche Discussion

  • A storm slab avalanche was reported from Jakes Peak, West Shore area yesterday.  Unknown details at this point.
  • Near-surface faceting during the long dry spell created weak snow in the top portion of the snowpack on some wind sheltered NW-N-NE aspects. Recent snow has buried this weak layer. It could become more of a problem since it will stay weak while the new snow consolidates and gains strength.
  • Variable snow surface conditions ranging from firm ice to soft snow still exist under the storm snow. While the storm snow should help smooth out the snow surfaces, it may not be enough to fully insulate backcountry travelers from the old snow surfaces, especially in steeper terrain. 
  • Snowmelt has sped up since the beginning of February. Many more obstacles (rocks, bushes, etc) and areas of bare ground have melted out on SE-S-SW aspects.

Regions covered