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.

Intermittent light rain and snow fell across the forecast area during the day yesterday with very little to no measurable accumulation. The snow level hovered around 7800 ft. during the afternoon. Overnight the skies started to clear and the winds started to shift as a high pressure ridge began working its way into the region. This ridge should bring continued clearing, warmer temperatures, and a decrease in the winds through the weekend. The forecast calls for daytime highs in the mid to upper 40's and cold clear nights with lows in the 20's above 7000 ft for the next two days.

Observations:

The Nov 18th facets continue to show signs of weakness. In the Mt. Rose backcountry yesterday, snowpit observations and stability tests still indicated that fractures can easily travel through this layer (snowpit). On slopes with anchors that poked through this weak layer, the fractures remained limited to snowpit tests and no whumpfs or large shooting cracks occurred. On slopes that had better coverage where a thicker facet layer and a thicker recent snow layer existed, the added weight of a person on the slope caused 20-35 ft shooting cracks (photo) and widespread whumpfing to occur as the facet layer broke and collapsed. In this area as in other areas around the region the Nov 18th facet layer remains weakest on the N-NE aspects above 8000 ft. both above and below treeline (pit profiles, videos, more info).  Wind loading had created some small wind slabs on NE facing test slopes in this area where small, skier-triggered cracking also occurred yesterday.

Avalanche Concern #1: Persistent slabs

The ingredients for avalanche activity still exist with the Nov 18 facet layer as a persistent weak layer and the recent snow on top of it as a slab layer. This combination will allow human-triggered avalanche activity to remain possible today in both above and below treeline terrain. In areas where the snowpack has this structure with a very shallow snowpack, anchors poking through the snowpack help prevent fractures in the weak layer from traveling very far. Of course, these same anchors also tend to damage skis, boards, snowmobiles, and people. The areas that hold a deeper snowpack and better recreation potential also hold the weakest snowpack. The N-NE aspects above 8000 ft. that had the most snow in Oct. and early Nov. represent these deeper and weaker slopes where the thickest and weakest facets exist under the largest slabs.

Avalanche Concern #2: Wind slabs

Strong winds and unconsolidated snow on the surface have combined to create hard wind slabs in near and above treeline areas. Some human-triggered cracking and small test slope failures have occurred at the interface between the wind slabs and the lighter snow below them. Due to the lack of snow on the windward aspects and decreasing winds, less wind slab formation should occur today and the snowpack should start to adjust to the recently formed wind slabs. Human-triggered hard slab avalanches will remain possible in the most heavily wind loaded areas near and above treeline on NW-N-NE-E aspects especially if the Nov 18th facet layer exists under the wind slabs.

The bottom line:

For areas above 8,000 ft. both above and below treeline, MODERATE avalanche danger exists on slopes 32 degrees and steeper on N-NE aspects. Pockets of MODERATE danger remain in the these areas on the NW and E aspects as well. The avalanche danger is LOW in all other areas.

Andy Anderson - Avalanche Forecaster, Tahoe National Forest

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

0600 temperature:	26-28 deg. F.
Max. temperature in the last 24 hours:	28-35 deg. F.
Average wind direction during the last 24 hours:	Southwest shifting towards the northwest early this morning
Average wind speed during the last 24 hours:	30 mph
Maximum wind gust in the last 24 hours:	76 mph
New snowfall in the last 24 hours:	trace inches
Total snow depth:	10-26 inches

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

For 7000-8000 ft:
	Friday:	Friday Night:	Saturday:
Weather:	Partly cloudy	Partly cloudy	Partly cloudy
Temperatures:	42-48 deg. F.	20-27 deg. F.	42-49 deg. F.
Wind direction:	West	Variable	Southwest
Wind speed:	15-25 mph with gusts to 40 mph decreasing to 10-15 mph in the afternoon	Light	Up to 10 mph with gusts to 25 mph in the afternoon
Expected snowfall:	O in.	O in.	O in.
For 8000-9000 ft:
	Friday:	Friday Night:	Saturday:
Weather:	Partly cloudy	Partly cloudy	Partly cloudy
Temperatures:	39-45 deg. F.	22-29 deg. F.	41-48 deg. F.
Wind direction:	West	South	South
Wind speed:	20-30 mph with gusts to 50 mph decreasing to 10-15 with gusts to 25 mph in the afternoon	10-15 mph with gusts to 25 mph becoming light overnight	10-15 mph with gusts to 25 mph in the afternoon
Expected snowfall:	O in.	O in.	O in.