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.

The storm system that impacted the region on Friday deposited more snow than forecast and more snow than was reported this morning by remote sensors. New snow amounts of up to 12 inches were confirmed today along the Sierra Crest in the Donner Summit area. Elsewhere new snow amounts range from 3 to 6 inches. Another storm system is expected to deposit an additional 3 to 7 inches of new snow along the Sierra Crest overnight tonight into tomorrow morning. Ridgetop winds have remained moderate in speed out of the west today and are expected to shift to the southwest tonight and remain moderate in speed as the next weather system affects the forecast area.

Observations:

Observations made today on Castle Peak (Donner Summit area) reveled 12 inches of new snow in wind protected areas above 8,000' and up to 18 inches of new snow in wind loaded areas. This new snow sits on top of older faceted snow that is acting as a weak layer and causing snowpack instability. Several whumpfs were triggered by the weight of a single skier on northerly aspects both below treeline and near treeline. Snowpit tests indicated fractures are likely to propagate along the top of this faceted layer in a variety of locations between 8,100' and 9,000' on north aspects (more info, videos, snowpits). Recent observations from around the forecast area have noted the presence of this faceted snow layer on northerly aspects above 8,000' prior to becoming buried by yesterday's snowfall (more info here).

Avalanche Concern: Persistent slabs

The faceted snow that formed on the ground during the first half of November is acting as a persistent weak layer. As this layer was buried yesterday, it will now be referred to as the November 18 facet layer. New snow on top of this layer is acting as the slab. Snowpack failure at this time is expected to occur a few inches above ground level leading to avalanches that are 1 to 2 feet deep. Areas that hold basal ice either held over from last winter or from the October 4-6 snowfall will have a more efficient bed surface, allowing for wider and farther traveling avalanches to occur. For the remainder of today human triggered avalanches remain possible both above and below treeline in areas above 8,000' on NW-N-NE-E aspects on slopes 32 degrees and steeper. Natural avalanches will become possible overnight tonight after the onset of more snowfall.

The bottom line:

Near and above treeline avalanche danger is MODERATE both above and below treeline in areas above 8,000' on NW-N-NE-E aspects on slopes 32 degrees and steeper. For all other areas, avalanche danger is LOW. Avalanche danger is expected to increase during the overnight hours with natural avalanches becoming possible.

Brandon Schwartz - Avalanche Forecaster, Tahoe National Forest

Weather Observations from along the Sierra Crest between 8200 ft and 8800 ft:

0600 temperature:	14 deg. F.
Max. temperature in the last 24 hours:	23 deg. F.
Average wind direction during the last 24 hours:	West
Average wind speed during the last 24 hours:	30 mph
Maximum wind gust in the last 24 hours:	57 mph
New snowfall in the last 24 hours:	6 to 12 north of Hwy 50, elsewhere 2 to 4 inches
Total snow depth:	8 to 22 inches

Two-Day Mountain Weather Forecast - Produced in partnership with the Reno NWS

For 7000-8000 ft:
	Saturday:	Saturday Night:	Sunday:
Weather:	Cloudy skies	Cloudy skies with a chance of snow in the evening. Snow after midnight.	Snow in the morning, then snow showers in the afternoon.
Temperatures:	17 to 23 deg. F.	13 to 20 deg. F.	23 to 30 deg. F.
Wind direction:	W	SW	SW
Wind speed:	15 to 20 with gusts to 35 mph.	20 to 30 mph with gusts to 40 mph.	Around 10 mph.
Expected snowfall:	O in.	1 to 3 in.	2 to 4 in.
For 8000-9000 ft:
	Saturday:	Saturday Night:	Sunday:
Weather:	Cloudy skies	Cloudy skies with a chance of snow in the evening. Snow after midnight.	Snow in the morning, then snow showers in the afternoon.
Temperatures:	15 to 20 deg. F.	10 to 17 deg. F.	28 to 34 deg. F.
Wind direction:	W	SW	SW
Wind speed:	20 to 30 mph with gusts to 50 mph.	20 to 30 mph with gusts to 50 mph.	10 to 20 mph with gusts to 35 mph.
Expected snowfall:	O in.	2 to 4 in.	2 to 4 in.