Avalanche forecast

Central Sierra Nevada

Sierra Avalanche Center
View on map

Avalanche danger

Alpine
1 · Low
Treeline
2 · Moderate
Below
2 · Moderate
Open full map
Out of date — this forecast expired 13 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

Pockets of MODERATE avalanche danger remain near treeline and below treeline on NW-N-NE aspects on slopes steeper than 32 degrees with consistent snow cover. This is due to lingering persistent slabs. In these areas, the possibility of human triggered avalanches remains ongoing. For all other areas avalanche danger is either LOW or non-existent due to the lack of snow cover.

Avalanche problems

  • Deep Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1

    Variability in avalanche danger exists around the forecast area. Persistent slabs linger in some areas near treeline and below treeline on NW-N-NE aspects where the faceted Dec 7 persistent weak layer remains unstable. Field observations from the past 3+ weeks have shown the greatest amount of ongoing instability with little to no week to week improvement in the Carson Pass and Pole Creek/Deep Creek areas. Observations from the Yuba Pass, Mount Rose, Donner Summit, West Shore Tahoe, and Echo Summit areas have shown significantly less ongoing instability and in some cases stable conditions near treeline and below treeline on NW-N-NE aspects.

    Triggering and going for a short ride in even a small avalanche at this time will almost certainly have significantly elevated consequences due to the almost guaranteed impact with rocks, logs, or trees due to the shallow snowpack. Becoming caught in the same size avalanche above a more typical deep Sierra snowpack could very well have minimal consequences.

Avalanche Discussion

Spatial variability exists around the forecast area and there are significant snowpack stability differences on near treeline and below treeline NW-N-NE aspects from one area to another. The persistent weak instability on the Dec 7 facet layer has improved greatly in some areas and remains quite unstable in other areas. Recent observations from around the forecast area have shown this spacial variability. In the Carson Pass area on Dec 31, travel on near treeline and below treeline N-NE aspects in the area south of Red Lake produced cracking and collapsing of the snowpack. Some of the collapses occurred on the same slopes and areas previously collapsed by the same forecaster traveling through the area on Dec 12. Click here and watch the video showing very impressive collapse and propagation of the faceted Dec 7 persistent weak layer along a 2 meter (6.6ft) wide extended column test in this area. It is an excellent illustrator of the ongoing snowpack instability that has persisted for nearly a month in the Carson Pass, Pole Creek, and Deep Creek areas. Other recent observations from the Yuba Pass, Donner Summit, West Shore Tahoe, and Mount Rose areas have shown better overall snowpack stability with little current weakness and propagation along the Dec 7 facet layer.

Avalanche danger on SE-S-SW-W aspects has been almost entirely eliminated due to melt. Some snow cover exists on E aspects, but the Dec 7 facet layer has not been observed at any elevation on E aspects. The Dec 7 facet layer is also absent above treeline on NW-N-NE aspects. This is allowing for LOW avalanche danger in these areas. Near treeline and below treeline on NW-N-NE aspects, continued snowpack settlement has reduced the overall snowpack height and allowed rocks, logs, and stumps to show through the snowpack in places that were previously covered.

Regions covered