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.

Expect one more day of unsettled weather with increasing clouds and isolated snow showers in the afternoon before change occurs. A significant storm system is expected to impact the forecast area late tonight through Monday with possible accumulations of 15 to 30 inches. Remote sensors above 8,000' are reporting air temperatures this morning in the low to mid teens. This is around 10 to 15 deg F colder than 24 hours ago. Ridgetop winds shifted to the NE for a few hours overnight before shifting to the SW ahead of the approaching storm system. Wind speeds are increasing this morning and are forecast to become strong from the SW today.

Recent observations from around the forecast area indicate that the upper portions of the snowpack are gaining strength, making it increasingly difficult to trigger snowpack failure down on the October 19 facet layer. Observations made yesterday on Silver Peak (Upper Pole Creek area) at 8,110' on a N aspect 30 degree slope near treeline showed a significant increase in snowpack strength over observations made in the same location on December 1. However, fracture propagation tests indicated that once sufficient force was applied, fracture propagation still occurs along the Oct 19 facet layer. All of the ingredients for causing a human triggered avalanche still exist (bed surface, weak layer, overlying slab) but the human trigger will either need to be large or near a shallow portion of the slab. Given the overall shallow snowpack with many exposed rocks, trees, and wind affected areas where a trigger point is more likely to be found, human triggered avalanches remain possible at this time. As significant amounts of new snow accumulate this week adding additional load to the existing snowpack, deep slab instability with failure on the Oct 19 layer will become an increasing concern.

For today, lingering pockets of snowpack instability remain the concern above 8,000' both near treeline and below treeline on NW-N-NE aspects where the October 19 facet layer exists. This layer is present on slopes that are at least somewhat sheltered from the recent NE winds that scoured away the Oct 19 layer above treeline. Between 8,000' to 8,600', the Oct 19 layer is at the bottom of the snowpack sitting on the ground. Above 8,600', the Oct 19 layer sits on top of the ice mass that formed in early October. In other areas where recent NE winds scoured away the Oct 19 facet layer, at lower elevations where the Oct 19 layer is absent or only slightly faceted, or on other aspects that have received more solar radiation, snowpack stability is significantly better. Pay attention to the snowpack as you travel anticipating the possibility of significant differences from one slope to another. Evaluate each new slope carefully using feet or poles to feel for the early Oct ice mass and by digging quick hand pits to look for the soft, sugary crystals of the Oct 19 facet layer either on top of the ice mass or at ground level. Slopes 32 degrees and steeper where the Oct 19 facet layer exists remain suspect.

The bottom line:

For most areas, avalanche danger is LOW. Isolated pockets of MODERATE avalanche danger exist above 8,000' both near treeline and below treeline on NW-N-NE aspects, 32 degrees and steeper.

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:	25 deg. F.
Average wind direction during the last 24 hours:	W shifting to NE shifting to SW
Average wind speed during the last 24 hours:	32 mph
Maximum wind gust in the last 24 hours:	61 mph
New snowfall in the last 24 hours:	0 to trace inches
Total snow depth:	8 to 20 inches

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

For 7000-8000 ft:
	Sunday:	Sunday Night:	Monday:
Weather:	Partly cloudy skies in the morning. Mostly cloudy with isolated snow showers in the afternoon.	Cloudy skies with snow developing by midnight.	Cloudy skies with snow.
Temperatures:	17 to 24 deg. F.	7 to 14 deg. F.	12 to 19 deg. F.
Wind direction:	SW	SW	SW shifting to SE in the afternoon.
Wind speed:	15 to 25 mph with gusts to 40 mph.	20 to 30 mph with gusts to 75 mph. Gusts decreasing to 55 mph after midnight.	10 to 20 mph with gusts to 40 mph in the morning. 10 to 20 mph with gusts to 30 mph in the afternoon.
Expected snowfall:	Trace in.	5 to 10 in.	10 to 20 in.
For 8000-9000 ft:
	Sunday:	Sunday Night:	Monday:
Weather:	Partly cloudy skies in the morning. Mostly cloudy with isolated snow showers in the afternoon.	Cloudy skies with a chance of snow in the evening, then snow after midnight.	Cloudy skies with snow.
Temperatures:	16 to 22 deg. F.	3 to 10 deg. F.	9 to 16 deg. F.
Wind direction:	SW	SW	SW shifting to SE in the afternoon.
Wind speed:	15 to 25 mph with gusts to 55 mph. Winds increasing to 30 to 45 mph with gusts to 75 mph in the afternoon.	25 to 40 mph with gusts to 75 mph.	20 to 30 mph with gusts to 60 mph. Winds decreasing to 15 to 25 mph with gusts to 45 mph in the afternoon.
Expected snowfall:	Trace in.	6 to 11 in.	12 to 20 in.