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 high pressure has started to form over the region. This ridge should bring warmer temperatures and clear skies to the forecast area. Daytime highs today should climb into the upper 20's and low 30's above 7000 ft. As the ridge establishes itself the wind should shift back to the west and southwest this afternoon. These winds should begin to increase over the next 36 hours due to another low pressure moving into the Pacific Northwest. This low may start to push some clouds into the area tomorrow; however, most of the mositure associated with this low should remain north of the region.

Observations:

Yesterday observations in the Mt. Rose backcoutry and on Hidden Peak show significant settlement within the storm snow. Handpits on Hidden Peak showed that the density change (lighter snow under heavier snow) still existed; however, stability tests, ski cuts, and cornice cuts did not produce any failures on this layer (photos, video). In the Mt Rose backcountry near a skier-triggered slide that occurred on Friday this interface also still exists. Stability tests in this area showed that fractures along this interface remain possible. The tests also showed that these fractures should be more difficult to trigger today (pit profile, photos).

Another natural avalanche that occurred near the end of the storm on Friday was also reported on Anderson Peak. This slide looked large and may have entrained all of the new snow as well as stepping down into some of the older snow (photos more info).

Avalanche Concern #1: Wind Slabs and Deep Slabs

Wind slabs that formed during the recent storm still exist on the wind-loaded NW-N-NE-E-SE aspects. In many areas the bonds between these slabs and the snow below them have strengthened enough to hold the wind slabs in place. However this strengthening has not occurred everywhere. Some of these slabs will remain sensitive to human-triggering today. On the wind-loaded N-NE-E and cross loaded NW and SE aspects pockets of fragile wind slabs should still linger. These pockets will most likely exist in near and above treeline terrain. Even though these slabs may be more difficult to trigger today, avalanches resulting from failure of these slabs could be large, deep, and destructive and could step down into older snow causing deep slab avalanches. Larger triggers like large cornices or multiple people on a slope will have better chances of causing avalanche activity.

Avalanche Concern #2: Rapid Warming

With lots of sunshine and daytime highs 10 degrees above yesterday's forecasted for today, the snowpack will experience some rapid warming. This rapid warming will cause rapid changes in the upper layers of the snowpack including decreased strength of the bonds holding the layers together and increased deformation in the layers. These rapid changes may occur too fast for the snowpack to adjust to them and stay in place. As the snowpack weakens due to today's rapid warming human-triggered avalanches will become possible on the sun exposed aspects where the most warming occurs. Most of these instabilities should manifest as point release avalanches and surface instabilities like roller balls; however, some slab avalanche activity will be possible as well. If slab avalanches do occur they could be large, deep and dangerous. The mid to lower elevation SE-S-SW aspects will hold the best potential for these kinds of slides with pockets of these instabilities existing on other less sun-exposed aspects and on higher elevation sun-exposed aspects.

The bottom line:

Near and above treeline, pockets of MODERATE avalanche danger will exist on all aspects, 35 degrees and steeper. Below treeline, avalanche danger is MODERATE on SE-S-SW aspects with pockets of MODERATE danger on E and W aspects, 35 degrees and steeper. Deep and destructive human triggered avalanches remain possible.

Andy Anderson - Avalanche Forecaster, Tahoe National Forest

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

0600 temperature:	8-10 deg. F.
Max. temperature in the last 24 hours:	12-22 deg. F.
Average wind direction during the last 24 hours:	Northeast
Average wind speed during the last 24 hours:	15 mph
Maximum wind gust in the last 24 hours:	32 mph
New snowfall in the last 24 hours:	O inches
Total snow depth:	94-139 inches

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

For 7000-8000 ft:
	Sunday:	Sunday Night:	Monday:
Weather:	Sunny	Mostly clear	Mostly sunny with some occasional thin high clouds
Temperatures:	28-34 deg. F.	13-19 deg. F.	26-31 deg. F.
Wind direction:	North shifting to the west in the afternoon	Southwest	Southwest
Wind speed:	Light increasing to 10-15 mph in the afternoon	10-20 mph with gusts to 35 mph	10-20 mph increasing to 15-25 with gusts gusts to 45 mph in the afternoon
Expected snowfall:	O in.	O in.	O in.
For 8000-9000 ft:
	Sunday:	Sunday Night:	Monday:
Weather:	Sunny	Mostly clear	Mostly sunny with some occasional thin high clouds
Temperatures:	24-29 deg. F.	15-20 deg. F.	21-26 deg. F.
Wind direction:	North shifting to the west in the afternoon	Southwest	Southwest
Wind speed:	10-20 mph with gusts to 35 mph increasing to 15-25 mph with gusts to 45 mph in the afternoon	15-30 mph with gusts to 60 mph	20-35 mph with gusts to 60 mph
Expected snowfall:	O in.	O in.	O in.