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.

Yesterday, 2-4 inches of snow accumulated across the forecast area during the day. By yesterday afternoon most of the show showers had stopped, and the southwest winds started to decrease and shift to the east and southeast. The winds remain light out of the south-southeast this morning. A low pressure system off the west coast will keep cloudy skies and snow flurries over the forecast area today. A second low pressure system should start to impact the forecast area tomorrow afternoon. The forecast calls for cloud cover and southwest winds to increase. This second system should bring more snow to the area starting Tuesday night.

Observations:

Yesterday observations from Mt. Judah showed some cracking near newly-formed cornices and in newly-formed wind-slabs. In the Mt. Rose backcountry (photo and video), a ski-cut triggered a small, soft-slab avalanche on a 35-degree, wind-loaded, NE test-slope. This soft-slab was about 35 ft wide and with a crown of 4-12 inches. Other less wind-loaded slopes nearby did not react to a skier's weight. No other avalanche activity was reported. This slide ran on a weakness within the new snow. Observations in both of these areas showed a variety of riding conditions. On exposed N-NE-E aspects the new snow fell on top of wind-scoured surfaces creating "dust-on-crust" conditions. On more sheltered northerly aspects the new snow landed on unconsolidated snow from the last storm. In the Mt Judah area a breakable crust existed under the new snow in some areas. Snowpits on sheltered slopes in these areas also showed that the persistent weak layer (Oct 19th facets) near the base of the snowpack is gaining strength. Recent observations from across the forecast area indicate that the strength and distribution of this layer remains variable. Most recent observations also indicate that the strong, well-consolidated snow above the facets makes failure of this layer due to human-triggering unlikely.

Avalanche concern #1:

Most of the wind-slabs that formed yesterday are small and shallow due to yesterday's limited snow accumulation. The light winds should keep them from growing today. These slabs should stabilize quickly. Dangerous avalanche activity resulting from failure of these wind slabs is unlikely today. However, a few small, isolated pockets of instability may still exist above treeline on the most heavily wind-loaded N-NE-E aspects steeper than 35 degrees.

Avalanche concern #2:

Deep-slab avalanche activity on sheltered NW-N-NE aspects below treeline above 8,000 ft. where old persistent weak layers exist remains unlikely but not impossible. In the unlikely event that avalanche activity does occur due to failure of this layer, the resulting avalanches will release without warning with crowns of 2-4 ft deep. These large avalanches would have dire consequences for those who triggered them. The uncertainty surrounding this layer's strength and distribution make stability evaluations on slopes with this layer unreliable and difficult.

 

The bottom line:

LOW avalanche danger exists at all elevations and on all aspects. LOW danger does not mean no danger. Even though avalanche activity is unlikely today, it is not impossible. Use normal caution when travelling in the backcountry.

Andy Anderson - Avalanche Forecaster, Tahoe National Forest

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

0600 temperature:	20 deg. F.
Max. temperature in the last 24 hours:	26 deg. F.
Average wind direction during the last 24 hours:	Southwest until 5 pm yesterday then shifting the the east and southeast overnight.
Average wind speed during the last 24 hours:	17 mph until 5 pm yesterday then decreasing to 10 mph
Maximum wind gust in the last 24 hours:	37 mph
New snowfall in the last 24 hours:	2-4 inches
Total snow depth:	34-55 inches

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

For 7000-8000 ft:
	Monday:	Monday Night:	Tuesday:
Weather:	Cloudy with a chance of snow showers.	Cloudy with a chance of snow.	Mostly cloudy in the morning. Cloudy with a chance of snow in the afternoon.
Temperatures:	24-31 deg. F.	13-20 deg. F.	24-31 deg. F.
Wind direction:	South	Variable	Southwest
Wind speed:	10 mph	Light	10-20 mph with gusts to 30 mph
Expected snowfall:	trace to .5 in.	up to 1 in.	trace to .5 in.
For 8000-9000 ft:
	Monday:	Monday Night:	Tuesday:
Weather:	Cloudy with a chance of snow showers.	Cloudy with a chance of snow.	Mostly cloudy in the morning. Cloudy with a chance of snow in the afternoon.
Temperatures:	18-25 deg. F.	10-17 deg. F.	20-28 deg. F.
Wind direction:	South	Southwest	West shifting to southwest in the afternoon
Wind speed:	10-15 mph	10-15 mph with gusts to 25 mph after midnight	15-25 mph with gusts to 35 mph increasing to 25-35 mph with gusts to 55 mph in the afternoon
Expected snowfall:	trace to .5 in.	up to 2 in.	trace to .5 in.