The 142nd and final avalanche advisory for the 2017/2018 season was published on April 22nd. Thank you to all who have supported the avalanche center through volunteer hours, field observations, and financial support.
Early season storms are building the basal layers for this season's snowpack. At this time of year, snowfall that accumulates on N and NE aspects will likely remain through the winter. Aspects with more sun exposure may remain subject to melt. It will all depend on how the weather progresses this fall.
A few areas of snow cover have resisted full melt out following the October 25 snowfall event. These exist mainly along the Sierra Crest on N and NE aspects above 7,800' to 8,100'. In these areas, shallow wet snow up to 10cm (4in) deep exists across a number of avalanche start zones. This is expected to be buried by new snowfall associated with the Halloween storm. Going forward through the Halloween storm, avalanche concerns are focused mainly on wind slabs. These wind slabs are most likely to form on wind loaded slopes directly below ridgelines and in gullies. Following the Halloween storm, it will also be worth monitoring the snowpack for faceted weak layer formation on shaded NW-N-NE aspects. It does not take a very deep slab to create an unforgiving avalanche. The shallow snowpack this time of year does not eliminate the risk of avalanches. It does increase the likelihood of impact with rocks and subsequent injury either while caught in a small avalanche or while attempting over snow travel.
During a storm wind loading can increase snow deposition rates by 2 to 10 times the rate that snow is falling from the sky. Similar deposition rates can occur during periods of blowing snow under sunny skies. Either way, this rapid loading can create enough snowpack instability for an avalanche to occur, despite only a few inches of snow on the ground in wind protected areas. Make constant observations as you travel, looking for indications of current or recent snowpack instability. The best indicator is recent avalanche activity. Other signs of snowpack instability including wind loading, collapse, audible whumpfing sounds, shooting cracks, and/or test slope failure. These are all indications that the snowpack in the immediate area is unstable. When signs of an unstable snowpack exist, the only additional factors needed for avalanche to occur are a slope steeper than 30 degrees and a trigger.
There are several excellent online avalanche education opportunities available to refresh and/or build your avalanche skills. Choose one from the drop down list under the "Education" tab at the top of this page.
Current remote weather station data as well as a general weather forecast for the area provided by the NWS can be found by clicking here.
This avalanche advisory is provided through a partnership between the Tahoe National Forest and the Sierra Avalanche Center. This advisory covers the Central Sierra Nevada Mountains between Yuba Pass on the north and Ebbetts Pass on the south. Click here for a map of the forecast area. This advisory applies only to backcountry areas outside established ski area boundaries. This advisory describes general avalanche conditions and local variations always occur. This advisory expires 24 hours after the posted time unless otherwise noted. The information in this advisory is provided by the USDA Forest Service who is solely responsible for its content.
This website is owned and maintained by the non-profit arm of the Sierra Avalanche Center. Some of the content is updated by the USDA avalanche forecasters including the forecasts and some observational data. The USDA is not responsible for any advertising, fund-raising events/information, or sponsorship information, or other content not related to the forecasts and the data pertaining to the forecasts.