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.

Cloud cover will increase this morning as moisture ahead of the next weather system moves into the forecast area. Light snow showers are expected today before the next significant snowfall occurs tonight and Wednesday. An additional 1 to 8 inches of new snow accumulated across the forecast area yesterday bringing 24 hour snow totals up to 1 to 11 inches. The greatest accumulations were observed along the Sierra Crest in the southern half of the forecast area. Air temperatures at 8,500' are in the upper teens to low 20s this morning. Around 2 to 5 degrees of daytime warming is expected. Ridgetop winds remain out of the southwest and increased from light to moderate in speed overnight. Ridgetop winds out of the south to southwest are expected to remain moderate in speed today.

Observations:

Observations made yesterday on Hidden Peak (West Shore Tahoe area) and on Mt. Tallac (Desolation Wilderness area) both showed significant instability within the top portion of the recent storm snow. Isolated small natural slab avalanches with additional human triggered slab avalanches were the theme. On Hidden Peak, a small natural avalanche large enough to bury or injure a person occurred along the summit ridge in near treeline terrain at 9,000' on an E aspect 40 degree slope. The avalanche measured 200' wide by 200' long with a crown depth of 6 to 12 inches. Two additional intentional skier triggered avalanches were very easily triggered on the slopes adjacent to the natural avalanche (photos, crown profile, more info). Snowpack failure occurred on a layer of lower density new snow below a slightly higher density new snow surface layer. High density snow from Sunday acted as the bed surface. Below treeline, widespread sluffing was observed on convex rolls steeper than 37 degrees. On Mt. Tallac, very similar slab and loose snow avalanche activity was observed. Evidence of a recent large avalanche from this past weekend was noted as well (photos, more info).

On Tamarack Peak (Mount Rose area) widespread cracking was noted upon departure from the parking lot and several intentional human triggered slab avalanches were triggered in wind loaded near treeline terrain on N aspect 35 to 38 degree slopes between 9,200' and 9,600'. Crown depths measured 6 to 18 inches with enough snow involved to bury or injure a person (photos, more info). The failure layer was noted as a density inversion that formed prior to rising snow levels on Sunday. As snow levels rose, higher density snow was deposited over lower density snow before snow levels fell and lighter density surface snow was deposited Sunday evening. This created a pronounced slab in the upper portion of the snowpack.

Avalanche Concern #1: Slab Avalanches

Slab avalanche activity will not be as widespread today as yesterday, but is still expected to occur. Human triggered slab avalanches remain possible and should be anticipated today above and below treeline on steep NW-N-NE-E-SE aspects. Most of the avalanche activity that occurs today is expected to involve the top 6 to 24 inches of recent storm snow. Density inversions that formed on both Sunday and Monday combined with some degree of new wind loading from increasing winds overnight are the anticipated failure layers. Isolated large slab avalanches with failure deeper in the recent storm snow layers are unlikely but not impossible.

Avalanche Concern #2: Loose snow avalanches

In steep wind protected areas below treeline, loose snow avalanches (sluffs) involving the top portion of the recent storm snow are expected to continue in areas where a slab does not exist. Secondary terrain hazards such as cliffs, terrain traps, trees, and exposed rocks will drastically increase the consequences of becoming caught in a loose snow avalanche.

 

The bottom line:

Avalanche danger is MODERATE above and below treeline on NW-N-NE-E-SE aspects 35 degrees and steeper. Avalanche danger is LOW with pockets of MODERATE danger on S-SW-W aspects above and below treeline 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 23 deg. F.
Max. temperature in the last 24 hours:	21 to 26 deg. F.
Average wind direction during the last 24 hours:	Southwest
Average wind speed during the last 24 hours:	29 mph
Maximum wind gust in the last 24 hours:	50 mph
New snowfall in the last 24 hours:	1 to 11 inches
Total snow depth:	72 to 99 inches

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

For 7000-8000 ft:
	Tuesday:	Tuesday Night:	Wednesday:
Weather:	Cloudy skies with scattered snow showers.	Cloudy skies with snow.	Cloudy skies with snow in the morning. Mostly cloudy skies with snow showers in the afternoon.
Temperatures:	26 to 31 deg. F.	23 to 28 deg. F.	26 to 31 deg. F.
Wind direction:	S	S shifting to SE after midnight.	SE shifting to W
Wind speed:	10 to 15 mph.	10 to 20 mph.	5 to 15 mph.
Expected snowfall:	0 to trace in.	1 to 3 in.	2 to 4 in.
For 8000-9000 ft:
	Tuesday:	Tuesday Night:	Wednesday:
Weather:	Cloudy skies with scattered snow showers.	Cloudy skies with snow.	Cloudy skies with snow in the morning. Mostly cloudy skies with snow showers in the afternoon.
Temperatures:	21 to 26 deg. F.	19 to 24 deg. F.	21 to 26 deg. F.
Wind direction:	S	S	S shifting to W
Wind speed:	15 to 30 mph with gusts to 45 mph.	20 to 35 mph with gusts to 55 mph.	20 to 30 mph with gusts to 45 mph in the morning. Winds decreasing to 10 to 20 mph with gusts to 35 mph in the afternoon.
Expected snowfall:	0 to trace in.	1 to 3 in.	2 to 4 in.