Avalanche forecast

Central Sierra Nevada

Sierra Avalanche Center
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Avalanche danger

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

MODERATE avalanche danger exists today as drifting snow forms new wind slabs near treeline and above treeline. Below treeline, LOW avalanche danger continues. Expect increasing avalanche danger at all elevations over the weekend.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1

    Ridgetop winds increased last night out of the SSW and are strong enough to move snow. With plenty of unconsolidated snow on the surface near ridgetops, areas of drifting snow are expected to form new wind slabs today even before snowfall begins. The vast majority of wind slabs will form near treeline and above treeline on NW-N-NE-E-SE aspects. Isolated wind slabs could form in other locations as well. Avalanche size up to D2 (large enough to bury or injure a person) is possible by early this afternoon in the most heavily wind loaded areas. Wind slabs will become increasingly widespread overnight as new snowfall combines with wind.

    Use blowing snow to identify areas of concern. Ridgetop areas where drifting snow is depositing, especially below cornice features and wind pillows will become increasingly suspect as the day progresses. Move cautiously around any areas where new wind slabs are forming, especially if snow surface cracking is present.

Avalanche Discussion

* Observations made yesterday in Davis Creek (Mount Rose area) showed increasing stability of old wind slabs formed during that last storm cycle. Minor amounts of skier triggered roller balls were noted from warming on E-SE aspects below about 7,500'. A thin sun crust may have have formed on the snow surface last night in lower elevation sun exposed areas.

* Some loose dry instability (surface sluffing) was reported yesterday in Shirley Canyon (near Squaw Valley) and to an isolated extent in the upper elevation portion of Davis Creek (Mount Rose area).

* The most recent reports of slab avalanche activity are wind slab avalanches from Feb 5 occurring on NE-E aspect terrain in Davis Creek (Mount Rose area) and near The Nipple in the Blue Lakes region of Carson Pass.

* Surface hoar up to 10 mm in size was reported yesterday from Mt. Judah (Donner Summit area) and from Shirley Canyon (near Squaw Valley).

Regions covered