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.

A storm system is expected to impact the forecast area Friday afternoon into Saturday morning. Total snowfall accumulations of 8 to 16 inches are expected along the Sierra Crest. Very strong southwest ridgetop winds with gusts up to 130 mph are forecast for late Friday. Snow levels are expected to start around 7,000' in the Lake Tahoe Basin and fall to below 3,500' with cold front passage Friday afternoon.

Observations made Wednesday at 9,100' on the NE aspect of Elephant's Back (Carson Pass area) and Thursday at 8,960' on the N aspect and at 9,090' on the NNE aspect of Mt. Lola (Independence Lake area) have revealed the presence of a 1 to 2 foot deep, weak snowpack on N and NE aspects above 8,000'. At the base of the snowpack is a 3 to 12 inch thick, very hard ice layer covering the ground.  This smooth ice is covered with a 2 to 3 inch layer of weak and poorly bonded faceted snow crystals. These facets are covered by a 2 to 5 inch slab of newer snow from the November 11th snowfall event. Individuals walking on foot through the snow have observed whumpfing and shooting cracks in these areas. Snowpit data and stability tests have indicated that this existing snowpack is in poor condition to handle new snow loading and that fracture propagation along the top of the faceted snow layer is possible. A similar ice layer with a few inches of new snow on top of it was observed on higher elevation N and NE aspects on Tamarack Peak (Mount Rose area) on November 14th. In all observed locations, areas on other aspects are either covered with the ice layer only, the ice layer and well bonded newer snow above it, or are bare ground.

Significant avalanche concerns exist for this upcoming storm period, especially in areas where snow cover already exists. On the N and NE aspects above 8,000', new snow loading on top of a weak snowpack structure will allow for the possibility of larger and more destructive avalanches. Greater concerns exist for these areas at this time. Natural and human triggered avalanches are a significant concern in areas where this snowpack exists.  In other areas, bonding of new snow to the old snow surface and any instability within the storm snow will be the causes of any avalanche activity.  Early season conditions exist with many exposed rocks, especially in avalanche runout zones.

The bottom line:

Fall Conditions Update

Despite very little snow on the ground, conditions are complex and the snowpack structure is weak. Pay attention out there!

Brandon Schwartz - Avalanche Forecaster, Tahoe National Forest

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

0600 temperature:	32 deg. F.
Max. temperature in the last 24 hours:	46 deg. F.
Average wind direction during the last 24 hours:	NW shifting to SW
Average wind speed during the last 24 hours:	30 mph
Maximum wind gust in the last 24 hours:	90 mph
New snowfall in the last 24 hours:	O inches
Total snow depth:	0 to 20 inches

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

For 7000-8000 ft:
	Friday:	Friday Night:	Saturday:
Weather:	Mostly cloudy skies in the morning with snow in the afternoon.	Cloudy skies with snow in the evening. Isolated showers after midnight.	Mostly cloudy skies with isolated snow showers in the morning.
Temperatures:	36 to 44 falling to 25 to 35 deg. F.	11 to 18 deg. F.	27 to 34 deg. F.
Wind direction:	SW	SW	W
Wind speed:	40 to 60 mph with gusts to 90 mph	20 to 30 mph with gusts to 60 mph, decreasing to 10 to 15 mph with gusts to 30 mph after midnight.	10 to 15 mph
Expected snowfall:	4 to 8 in.	4 to 8 in.	O in.
For 8000-9000 ft:
	Friday:	Friday Night:	Saturday:
Weather:	Mostly cloudy skies in the morning with snow in the afternoon.	Cloudy skies with snow in the evening. Isolated showers after midnight.	Mostly cloudy skies with isolated snow showers in the morning.
Temperatures:	32 to 38 falling to 18 to 25 deg. F.	7 to 14 deg. F.	23 to 30 deg. F.
Wind direction:	SW	SW shifting to W	W shifting to NW
Wind speed:	60 to 80 mph with gusts to 130 mph	45 to 60 mph with gusts to 105 mph. Winds decreasing to 15 to 25 mph with gusts to 40 mph after midnight.	15 to 25 mph decreasing to 10 to 15 mph in the afternoon.
Expected snowfall:	4 to 8 in.	4 to 8 in.	O in.