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 significant storm cycle continues to impact the forecast area this morning with a period of high intensity precipitation forecast for this afternoon through the overnight hours. Storm totals from the past 24 hours are running 10 to 15 inches at 8,000' with 7 to 8 inches of accumulation last night. Light to moderate snowfall is expected this morning before snowfall rates of 2 to 3 inches per hour begin around noon and continue overnight. Additional snowfall amounts of 26 to 40 inches are expected above 8,000' in the next 24 hours. Ridgetop winds have remained moderate to strong in speed out of the southwest for the past 24 hours. Ridgetop winds are expected to continue in this fashion through today and into the overnight hours. Air temperatures at 8,000' are expected to remain in the mid twenty's today.

Yesterday, observations made in the Independence Lake area on 32 to 36 degree NW and N aspect road cuts below treeline at 7,100' indicated that basal facets in this area are weak. Fracture propagation tests (photos) indicated that fracture propagation is likely through this layer as significant new snow loading is added to the snowpack over the next 24 hours. Observations made on Friday near the Mount Rose Hwy Summit revealed a reawakening of instability on the October 19 facet layer below treeline on a NW aspect, 31 degree slope at 8,900' (videos). This morning, significant wind loading with isolated natural avalanche activity has been reported above treeline on N and NE aspects along the Sierra Crest in the northern half of the forecast area.

Avalanche concern #1:

Wind loading and unstable slab formation already exists this morning on N and NE aspects and will increase this afternoon as snowfall rates increase. Above treeline areas on NW-N-NE-E aspects will receive the greatest amounts of wind loading. Natural avalanches are expected today in these areas. SE aspects will receive some cross loading and hold subsequent snowpack instability today which may increase overnight as winds shift to the west tonight and snowfall continues.

Avalanche concern #2:

Deep slab instability is expected to occur in below treeline areas as the October 19 facet layer and possibly the November 22 thin rain crust/facet layer become overloaded by significant accumulation of higher density new snow during the next 24 hours. A variety of weak layers are known to exist near treeline and below treeline in the lower and middle portions of the snowpack near and above 7,000' on NE wind protected NW-N-NE aspects throughout the forecast area. These weak layers vary by location and individual slopes, taking the form of either basal facets (Sierra Crest and Carson Range), facets on top of the early October basal ice mass (Sierra Crest and Carson Range above 8,600'), and as small faceted crystals on top of the thin Nov 22 rain crust (Sierra Crest only up to 9,000'). Stability tests and fracture propagation tests performed over the past several days indicate that significant avalanche activity is possible below treeline once these weak layers become overloaded and snowpack failure occurs. This is a situation that is unusual for this region. Backcountry travelers cannot afford to be lulled into a sense of security below treeline at this time.

The bottom line:

Avalanche danger is HIGH today in wind loaded areas near and above treeline on NW-N-NE-E aspects, 34 degrees and steeper. Near treeline and below treeline, avalanche danger is expected to rise to HIGH danger on NW-N-NE aspects near and above 7,000' on slopes 32 degrees and steeper, due to overloading of persistent weak layers near the base of the snowpack. In other areas, avalanche danger will range from MODERATE to CONSIDERABLE today.

Brandon Schwartz - Avalanche Forecaster, Tahoe National Forest

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

0600 temperature:	24 deg. F.
Max. temperature in the last 24 hours:	28 deg. F.
Average wind direction during the last 24 hours:	Southwest
Average wind speed during the last 24 hours:	46 mph
Maximum wind gust in the last 24 hours:	87 mph
New snowfall in the last 24 hours:	10 to 15 inches
Total snow depth:	30 to 50 inches

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

For 7000-8000 ft:
	Saturday:	Saturday Night:	Sunday:
Weather:	Cloudy skies with snow, heavy from mid day on.	Cloudy skies with high intensity snowfall.	Cloudy skies with snow in the morning. A chance of snow in the afternoon.
Temperatures:	26 to 33 deg. F.	14 to 21 deg. F.	24 to 31 deg. F.
Wind direction:	SW	SW	SW
Wind speed:	15 to 25 mph with gusts to 35 mph. Gusts increasing to 45 mph in the afternoon.	20 to 30 mph with gusts to 45 mph. Gusts decreasing to 35 mph after midnight.	15 to 25 mph with gusts to 55 mph. Gusts decreasing to 45 mph in the afternoon.
Expected snowfall:	6 to 10 in.	16 to 22 in.	5 to 8 in.
For 8000-9000 ft:
	Saturday:	Saturday Night:	Sunday:
Weather:	Cloudy skies with snow, heavy from mid day on.	Cloudy skies with high intensity snowfall.	Cloudy skies with snow in the morning. A chance of snow in the afternoon.
Temperatures:	22 to 29 deg. F.	10 to 17 deg. F.	25 to 31 deg. F.
Wind direction:	SW	SW shifting to W	SW
Wind speed:	20 to 50 mph with gusts to 65 mph. Increasing to 50 to 65 mph with gusts to 85 mph in the afternoon.	45 to 55 mph with gusts to 85 mph. Decresing to 25 to 40 mph with gusts to 65 mph after midnight.	30 to 45 mph with gusts to 75 mph. Decreasing to 25 to 35 mph with gusts to 65 mph in the afternoon.
Expected snowfall:	8 to 12 in.	18 to 28 in.	6 to 10 in.