The usable snowpack exists along the Sierra Crest in the northern portion of the forecast area. Areas above 7,000' and north of Tahoe City have sufficient amounts of supportable snow for quality over snow travel (2 to 3 feet). Along the Sierra Crest south of Tahoe City, snowpack depths decrease dramatically, even at the highest elevations. In these areas the snowpack is unusable for skiing/boarding/snowmobiling. The Mount Rose area in the NE portion of the forecast area has decent snowcover (~2 feet) in areas that have held snow/ice since mid Oct. This is generally N aspects above 9,300'. Below 9,300' on N aspects or on all other aspects in the Mount Rose area, over snow travel is possible, but impact with rocks is likely with snow depths around 1 foot.
The number of snowpack observations collected by the avalanche center remains limited at this time. There are a few areas of concern that have emerged. True N aspects above 8,300' along the northern Sierra Crest portion of the forecast area and on true N aspects above 9,000'-9,300' in the Mount Rose portion of the forecast area hold the most concerning snowpack structure. In these areas, 1 to 2 feet of recent new snow sits on top of a layer of faceted old snow crystals that is sandwiched as a weak layer between the new snow and a thick ice layer below. On all other aspects, including NW and NE aspects the recent new snow was deposited onto bare ground or directly onto ice without the faceted snow layer.
In the southern portion of the forecast area where significantly lesser amounts of both old snow and recent storm snow exist, any faceted snow on N aspects remains well anchored and peppered with exposed rocks.
More small to moderate storms this week are expected to bring additional snow, mainly to the northern portion of the forecast area. Wind slab and persistent slab avalanche problems could form. Identify areas of active or recent wind loading. Travel conservatively on N aspects where facets may exist directly above easy to identify basal ice.
Don't forget about past avalanches that occurred locally in the shallow early season Novermber/December snowpacks. It is that time of year. A few are linked here: Nov 11, 2015 Elephant's Back, Dec 1, 2014 Round Top, Nov 28, 2010 Red Lake Peak, Nov 21, 2009 Mount Rose Gaz-Ex chutes.
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.
For a recorded version of the Avalanche Advisory call (530) 587-3558 x258