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 cold front moving through the forecast area this morning is causing gale force winds and light precipitation. Ridgetop winds out of the southwest gusting to 100 mph will continue through mid morning before decreasing in speed this afternoon. New snow amounts are running around 1 to 2 inches along the Sierra Crest above 7,500'-8,000' with rain below. Up to an additional 2 inches is forecast for this morning along the Sierra Crest above 7,000'.  Little to no precipitation is spilling over to the east side of the forecast area. Wind and precipitation is expected to come to an end by tonight with sunshine and light winds returning to the forecast area for Thursday.

Recent Observations:

Observations made yesterday in the Mount Rose area continued to show ongoing instability focused on a persistent weak layer of faceted snow crystals at the base of the snowpack. Snowpit data collected over the past two days on Tamarack Peak has shown that the recent storm snow has become a cohesive slab, well bonded to itself but poorly bonded to the weak basal facets below. This layer has been observed on N to NE aspects mainly above 9,500'. In snowpit tests, this facet layer collapsed easily and propagated cleanly, (videos, more info). This layer appears weakest on slopes that received little to no traffic prior to the most recent snowfall.

Yesterday on South Maggies Peak (Desolation Wilderness area), only a couple of inches of new snow existed on all aspects up to about 7,500'. Above 7,500' the snowpack increased to around 1.5 feet deep on northerly aspects with recent storm snow sitting on top of rain affected old snow layers.The recent storm snow was well bonded to the rain crusts below and showed no evidence of near crust faceting (pit profile, more info). Wind transport of old snow was visible above treeline on nearby Mt. Tallac.

Today's Primary Avalanche Concern: Wind Slabs

Isolated areas of lingering old wind slab instability combined with newly formed wind slabs yesterday, last night, and this morning will keep wind slab concerns ongoing. Snowpack failure 1 to 2.5 feet deep is possible in the areas of greatest wind loading. This hazard will occur mainly near and above treeline on NW-N-NE aspects. Natural avalanche activity is unlikely. Human triggered avalanches are possible.

Today's Secondary Avalanche Concern: Persistent Slabs

This concern has only been observed in the Mount Rose area where a persistent weak layer of basal facets exists below the recent storm snow. The facet layer is most well developed on N to NE aspects above 9,500'. This is the type of avalanche concern where snowpack failure and subsequent avalanche could very well occur on a slope that already has numerous tracks on it. Natural avalanches involving this weak layer are unlikely. Human triggered avalanches involving this weak layer will remain possible for at least the next several days. Perform due diligence in slope by slope stability evaluations.

The bottom line:

Near and above treeline, pockets of MODERATE avalanche danger exist on NW-N-NE aspects on slopes 35 degrees and steeper due to recently formed wind slabs and ongoing persistent slabs. For all other areas, avalanche danger is LOW. The next update to this advisory will occur on Friday, November 23rd.

Brandon Schwartz - Avalanche Forecaster, Tahoe National Forest

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

0600 temperature:	30 to 36 deg. F.
Max. temperature in the last 24 hours:	32 to 38 deg. F.
Average wind direction during the last 24 hours:	Southwest
Average wind speed during the last 24 hours:	61 mph
Maximum wind gust in the last 24 hours:	100 mph
New snowfall in the last 24 hours:	1 to 3 inches
Total snow depth:	19 to 32 inches

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

For 7000-8000 ft:
	Wednesday:	Wednesday Night:	Thursday:
Weather:	Cloudy skies with snow in the morning. A chance of rain and snow in the afternoon.	Partly cloudy skies with a slight chance of snow showers in the evening.	Partly cloudy skies.
Temperatures:	37 to 43 deg. F.	20 to 27 deg. F.	40 to 47 deg. F.
Wind direction:	SW	SW	Variable
Wind speed:	40 to 45 with gusts to 70 mph, decreasing to 30 to 35 mph with gusts to 50 mph in the afternoon.	20 to 25 mph with gusts to 40 mph in the evening, becoming light.	Light winds
Expected snowfall:	West of Hwy 89, up to 2 in.	O in.	O in.
For 8000-9000 ft:
	Wednesday:	Wednesday Night:	Thursday:
Weather:	Cloudy skies with snow likely in the morning. A chance of snow in the afternoon.	Partly cloudy skies with a slight chance of snow showers in the evening.	Sunny skies.
Temperatures:	31 to 37 deg. F.	22 to 29 deg. F.	38 to 45 deg. F.
Wind direction:	SW	SW	S
Wind speed:	50 to 55 mph with gusts to 100 mph, decreasing to 40 to 45 mph with gusts to 70 mph in the afternoon.	30 to 35 with gusts to 55 mph in the evening becoming light.	Light winds increasing to 10 to 15 mph with gusts to 20 mph in the afternoon.
Expected snowfall:	West of Hwy 89, up to 2 in.	O in.	O in.