The Sierra Avalanche Center is reporting finding multiple weak layers in the Lake Tahoe snowpack. We know that we are all fired up to get out there and get some of this new powder snow, but lets all be intelligent and conservative out there. If there are multiple weak layers in the snowpack, it’s time to be very conservative.
Widespread areas of CONSIDERABLE avalanche danger exist near and above treeline on NW-N-NE-E-SE aspects 30 degrees and steeper due to newly formed wind slabs and below treeline on NW-N-NE aspects 30 degrees and steeper due topersistent slabs. Natural avalanches are possible, human triggered avalanches are likely today. Significant avalanche danger exists below treeline. — Everyone is chomping at the bit to get out there today. Only a small percentage have a handle on the weakness of the existing snowpack and the reality of avalanches today. Conservative terrain selection and effective group communication are imperative. – Sierra Avalanche Center
The snowpack so far this season has been built a few inches at at time, not feet at a time in typical Sierra fashion. As a result the existing snowpack is weak with many weak layers. It is more like a snowpack that is commonly experienced in the Rockies, Tetons, or Wasatch than in the Sierra Nevada.
Observations collected from around the forecast area over the past few weeks have shown that the existing snowpack is weak and in poor condition to handle new snow loading. Near treeline and below treeline areas that are above 7,500′ on NW-N-NE aspects held 1 to 2 feet of weak faceted(sugary) snow, eroding crusts, and surface hoar prior to the current snowfall. The vast majority of above treeline areas were significantly scoured by ENE winds Nov 21-23, removing most of the previous snow cover.
Observations made yesterday below Grouse Rocks (Ward Canyon area) revealed multiple weak layers within the snowpack on northerly aspects. Surface hoar was prevalent in open areas below treeline. Near crust facets on top of the upper most crust in the snowpack produced propagatingfailures in snowpit tests. For the most part, a significant slab was absent from above the most problematic weak layers yesterday (video, photo, pit profile, more info). Now that significant amounts of new snow have been added overnight, the slab is now there and additional load has been placed on these weak layers.
Read the Full Sierra Avalanche Center Avalanche Advisory here: