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.

The region should experience another spring-like day with sunny skies, light winds, and daytime highs in the upper 40's to low 50's above 7000 ft. The high pressure ridge driving this weather should remain over the forecast area for the rest of the week. The forecast calls for similar albeit slightly warmer conditions tomorrow.

Recent Observations:

Yesterday observations on Mt. Tallac (videos, more info) and on Tamarack Peak (video, snowpit, more info) both revealed layers of weak sugary snow (March 6th facets) around the old rain crust below the recent snow. On Mt. Tallac some tests indicated that fractures could travel through these facets and others indicated that propagation remains unlikely. The weakest and most well developed facet/crust combo existed on N-NE aspects between 8500 ft and 9100 ft. On N-NE facing aspects between 8600 ft and 9400 ft along the east ridge of Tamarack Peak, test results consistently indicated that these facets could break and the resulting fractures could propagate along the weak layer. On the E aspects in this area this crust/facet combo became less continuous and more inconsistent. In both of these areas, wet sticky snow started forming on any slopes that received sunshine yesterday. Some small roller balls and wet snow sluffs did occur near exposed rocks and as a result of ski cuts on the SE-S-SW aspects of Incline Lake Peak and on Mt. Tallac.

Avalanche Problem #1: Persistent Slabs

In some areas the recent snow has formed soft slabs on top of crusts with persistent weak layers of sugary snow (facets) around those crusts. In other areas either this persistent weak layer does not exist, the weak layer is not continuous, the crusts remain thick and strong, or the NE winds have scoured much of the soft slab away. In the areas where soft slabs sit on weak layers, two of the ingredients necessary for an avalanche exist: the slab and the weak layer. All that is missing is the right trigger on the right slope. Human triggered avalanches will remain possible on NW-N-NE aspects where a soft slab of recent snow exists on top of a persistent weak layer.

Digging into the snowpack represents one of the best ways to determine if this weak layer exists below the recent snow. In some areas other more obvious signs of instability such as collapsing and whumphing may exist, and in other areas these obvious clues may not exist. In some areas these kind of avalanches may be difficult to trigger and in others triggering them will remain possible.

Avalanche Problem #2: Wind Slabs

Firm wind slabs exist on the near and above treeline SE-S-SW-W-NW aspects and some older wind slabs may still exist on the N-NE aspects. Even though these wind slabs should become more difficult to trigger as they bond to the snow below them, human triggered avalanches involving these wind slabs may remain possible today in some places. These slabs should remain limited to areas near ridgelines where the most wind loading has occurred.

Avalanche Problem #3: Wet Avalanches

The combination of warm temperatures at all elevations and March sunshine will allow wet snow instabilities to form today. Natural and human triggered loose wet roller balls, pinwheels, and point releases should comprise most of the wet snow instabilities. It is not impossible that a wet slab avalanche could occur today on the most sun-exposed slopes where significant recent snow exists. The sun-exposed SE-S-SW aspects represent the most likely places for wet snow instabilities to form. Some wet snow instabilities could also form on E and W aspects.

The bottom line:

Both above and below treeline, areas of MODERATE avalanche danger exist on all aspects on slopes 35 degrees and steeper due to a combination of persistent slabs, wind slabs, and wet snow instabilities. Human triggered avalanches remain possible today. Areas of instability may exist near areas of stable snow.

Andy Anderson - Avalanche Forecaster, Tahoe National Forest

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

0600 temperature:	32-40 deg. F.
Max. temperature in the last 24 hours:	47-54 deg. F.
Average wind direction during the last 24 hours:	Variable
Average wind speed during the last 24 hours:	5-10 mph
Maximum wind gust in the last 24 hours:	22 mph
New snowfall in the last 24 hours:	O inches
Total snow depth:	59-90 inches

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

For 7000-8000 ft:
	Tuesday:	Tuesday Night:	Wednesday:
Weather:	Sunny	Clear	Sunny
Temperatures:	47-54 deg. F.	30-36 deg. F.	50-57 deg. F.
Wind direction:	Variable	Variable	Variable
Wind speed:	Light	Light	Light
Expected snowfall:	O in.	O in.	O in.
For 8000-9000 ft:
	Tuesday:	Tuesday Night:	Wednesday:
Weather:	Sunny	Clear	Sunny
Temperatures:	47-53 deg. F.	32-38 deg. F.	49-55 deg. F.
Wind direction:	Southwest	Southwest	Southwest
Wind speed:	5-15 mph with gusts to 25 mph in the afternoon	5-15 mph	5-15 mph with gusts to 25 mph
Expected snowfall:	O in.	O in.	O in.