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 weather system passing to the north of the forecast area today will bring strong to gale force winds and light snow showers to the forecast area today. New snow amounts above 7,000' from the past 24 hours are measuring 8 to 12 inches along the Sierra Crest from around Emerald Bay northward with 3 to 5 inches of new snow in the southern and eastern portions of the forecast area. Southwest ridgetop winds exceeded forecast speed expectations yesterday afternoon and became gale force with gusts up to 124 mph. Strong southwest winds this morning are expected to increase to gale force again this afternoon. Clearing skies, moderate winds, and significant warming are expected for tomorrow.

Observations:

Observations made yesterday on Hidden Peak (West Shore Tahoe area) revealed evidence of instability limited to the most recent storm snow. An intentionally skier triggered avalanche occurred below treeline at 8,620' on an E aspect convex slope with a angle of 41 degrees. The shallow slab measured 4 to 6 inches deep, 20' wide, and ran 150' down slope. The slab consisted of higher density new snow over lower density recent storm snow. No evidence of instability was observed below treeline on slopes less than 37 degrees in slope angle. Along the summit ridge around 9,200', skier triggered shooting cracks were common, failing 8 inches deep in a surface wind slab over lower density recent storm snow (photos, more info).

On Becker Peak (Echo Summit area) a surface wind slab 2 to 8 inches thick was widespread in lee areas near treeline with cracking limited to slopes that were undercut before loading from above. Very weak and sensitive cornices were easy to collapse failing as far as 15' back from the edge (photo, pit profile, more info). On Tamarack Peak (Mount Rose area) very weak and sensitive cornices were also reported with skier triggered collapse of cornice sections up to 150' wide occurring 5' back from the edge (more info).

Significant settlement of new snow has been observed in all areas during the storm cycle over the past several days.

Avalanche Concern #1: Wind Slabs

Continued wind transport of snow yesterday and today keeps the concern for unstable wind slabs ongoing. Widespread cracking that was observed yesterday is expected to continue today in wind loaded areas both above and below treeline. Near and above treeline areas on NW-N-NE-E-SE aspects will hold the largest slabs. This same instability will carry over into wind loaded below treeline areas as well. Most wind slabs are expected to remain around 1 foot deep or less. Larger slabs are possible in isolated areas, especially in response to triggers such as collapse of large cornice sections.

Avalanche Concern #2: Storm Snow Weaknesses

Areas with lingering instabilities within the recent storm snow are expected today due to the density changes and rimed snow crystals that have been observed within the upper portion of the snowpack over the past several days in both wind affected and wind protected areas. This instability is expected as isolated slab failure limited to the top 1 foot of the snowpack. Avalanche activity that fails on storm snow weaknesses today is expected to be human triggered and occur in steep areas near treeline or below treeline. Failures on this instability may occur within greater areas of seemingly stable snow.

Avalanche Concern #3: Minor Warming Instability

As slight warming occurs today with some sun breaks minor warming instability is possible, especially at lower and mid elevations and in areas along the eastern side of the forecast area. Roller balls and shallow surface slabs of warmer cohesive snow are possible today mainly on E-SE-S-SW aspects. More widespread and significant warming instability is expected tomorrow.

The bottom line:

Near and above treeline, avalanche danger is MODERATE on NW-N-NE-E-SE aspects on slopes 35 degrees and steeper. Below treeline, avalanche danger is LOW with pockets of MODERATE danger on all aspects in open areas on slopes 37 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:	19 to 24 deg. F.
Max. temperature in the last 24 hours:	24 to 28 deg. F.
Average wind direction during the last 24 hours:	Southwest
Average wind speed during the last 24 hours:	66 mph
Maximum wind gust in the last 24 hours:	124 mph
New snowfall in the last 24 hours:	3 to 12 inches
Total snow depth:	135 to 203 inches

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

For 7000-8000 ft:
	Sunday:	Sunday Night:	Monday:
Weather:	Mostly cloudy skies with isolated snow showers in the morning and scattered snow showers in the afternoon.	Mostly cloudy skies with a chance of snow showers in the evening, becoming partly cloudy.	Partly cloudy skies.
Temperatures:	29 to 35 deg. F.	17 to 24 deg. F.	34 to 40 deg. F.
Wind direction:	SW	SW	W
Wind speed:	15 to 30 mph with gusts to 45 mph. Winds incresing to 20 to 30 mph with gusts to 55 mph in the afternoon.	20 to 30 mph with gusts to 50 mph.	10 to 15 mph with gusts to 35 mph.
Expected snowfall:	Up to 1 in.	0 to trace in.	O in.
For 8000-9000 ft:
	Sunday:	Sunday Night:	Monday:
Weather:	Mostly cloudy skies with isolated snow showers in the morning and scattered snow showers in the afternoon.	Mostly cloudy skies with a chance of snow showers in the evening, becoming partly cloudy.	Partly cloudy skies.
Temperatures:	23 to 29 deg. F.	16 to 23 deg. F.	30 to 37 deg. F.
Wind direction:	SW	SW shifting to W	NW
Wind speed:	25 to 35 mph with gusts to 60 mph. Winds increasing to 35 to 50 mph with gusts to 75 mph in the afternoon.	45 to 55 mph shifting and decreasing to 30 to 40 mph after midnight. Gusts up to 80 mph.	20 to 30 mph with gusts to 55 mph.
Expected snowfall:	Up to 3 in.	0 to trace in.	O in.