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 fast moving storm system brought snow to the forecast area last night. New snow accumulations of 5 to 8 inches occurred along the Sierra Crest while 1 to 3 inches accumulated in the Carson Range. Snow shower activity is expected to continue into this afternoon before a break in snowfall occurs tonight and Monday. Southwest ridgetop winds were very strong yesterday with remote sensors reporting gusts to 123 mph over the Sierra Crest. Winds have decreased to moderate to strong in speed this morning and are forecast to decrease a bit more as the day progresses. Air temperatures that rose to near to above freezing at most locations yesterday have fallen overnight with cold front passage. Remote sensors are reporting air temperatures at 8,500' in the mid to upper teens this morning. Air temperatures are expected to warm into the mid to upper 20s above 7,000' today.

Observations:

Observations made yesterday on Trimmer Peak (Luther Pass area) revealed a stable snowpack in below treeline areas. A well bonded mix of unconsolidated surface snow over rain crust and/or higher density snow exists on most NW-N-NE-E aspects. Surface hoar was observed in several shaded wind protected areas below treeline between 7,400' and 8,200' (photos, pit profile, more info). Gale force winds ahead of the the approaching storm system caused very significant wind transport of snow yesterday along the Sierra Crest from the West Shore Tahoe and Desolation Wilderness areas all the way north through the Donner Summit and Independence Lake areas (photos, more info). Kirkwood Professional Ski Patrol also reported wind transport of old snow yesterday along ridges.

This morning, easy shears within last night's new snow were observed at the snow study plots at both Kirkwood Mountain Resort and Squaw Valley Ski Area. Since this is a weakness within the storm snow, it is expected to exist in the surrounding backcountry as well.

Avalanche concern #1: Wind Slabs

Very strong to gale force winds before, during, and after last night's snowfall are expected to have created widespread wind slabs in open wind loaded areas above and below treeline. The addition of new snow last night has further increased the size of new wind slabs that formed over the past 24 hours. Continued southwest winds combined with snow showers will allow for the ongoing possibility of natural avalanche activity this morning. Human triggered avalanches large enough to bury or injure a person are expected to occur today in wind loaded areas. The areas of greatest instability are expected along the Sierra Crest in near and above treeline terrain on N-NE-E aspects. Cross loaded NW and SE aspects are of concern as well. Due to the very strong wind speeds that have occurred, wind slabs area expected in open below treeline areas and along wind exposed below treeline ridges.

Avalanche concern #2: Buried surface hoar

Surface hoar that was observed mid day yesterday on shaded wind protected slopes below treeline between 7,400' and 8,200' on Trimmer Peak (Luther Pass area) may have survived yesterday's strong winds and above freezing air temperatures and become buried. This layer may also exist in other similar terrain around the forecast area. If this surface hoar was buried and preserved under new snow last night, a very weak layer will exist at the base of the new snow.  A high degree of uncertainty surrounds this avalanche concern due to unknown distribution and persistence around the forecast area.

The bottom line:

Near and above treeline, avalanche danger is MODERATE with pockets of CONSIDERABLE danger on N-NE-E aspects, 32 degrees and steeper. Below treeline, areas of MODERATE avalanche danger exist on all aspects, 32 degrees and steeper. Areas of CONSIDERABLE danger are only expected to exist near the Sierra Crest.

Brandon Schwartz - Avalanche Forecaster, Tahoe National Forest

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

0600 temperature:	15 to 19 deg. F.
Max. temperature in the last 24 hours:	34 to 41 deg. F.
Average wind direction during the last 24 hours:	Southwest
Average wind speed during the last 24 hours:	55 mph
Maximum wind gust in the last 24 hours:	123 mph
New snowfall in the last 24 hours:	1 to 8 inches
Total snow depth:	63 to 91 inches

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

For 7000-8000 ft:
	Sunday:	Sunday Night:	Monday:
Weather:	Cloudy skies with scattered snow showers in the morning. Partly cloudy skies with isolated snow showers in the afternoon.	Mostly cloudy skies with a slight chance of snow showers in the evening.	Mostly cloudy skies.
Temperatures:	23 to 30 deg. F.	14 to 20 deg. F.	28 to 35 deg. F.
Wind direction:	SW	SW	Variable
Wind speed:	15 to 25 mph with gusts to 40 mph. Gusts decreasing to 30 mph in the afternoon.	10 to 15 mph with gusts to 25 mph. Winds decreasing to around 10 mph after midnight.	Light winds.
Expected snowfall:	Trace to 2 in.	0 to trace in.	O in.
For 8000-9000 ft:
	Sunday:	Sunday Night:	Monday:
Weather:	Cloudy skies with scattered snow showers in the morning. Partly cloudy skies with isolated snow showers in the afternoon.	Mostly cloudy skies with a slight chance of snow showers in the evening.	Mostly cloudy skies.
Temperatures:	21 to 27 deg. F.	13 to 19 deg. F.	25 to 32 deg. F.
Wind direction:	SW	SW shifting to W	W
Wind speed:	30 to 45 mph with gusts to 70 mph. Winds decreasing to 25 to 35 mph with gusts to 55 mph in the afternoon.	25 to 35 mph with gusts to 55 mph. Winds decreasing to 15 to 20 mph with gusts to 40 mph after midnight.	Up to 10 mph.
Expected snowfall:	Trace to 2 in.	0 to trace in.	O in.