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.

Partly cloudy skies and light to moderate winds are expected across the forecast area today. An additional 2 to 5 inches of new snow accumulated during the past 24 hours, mainly prior to 9am yesterday. Clearing skies last night have allowed air temperatures to plummet into the single digits to low teens across the forecast area this morning. Ridgetop winds shifted from southwest to west yesterday evening. Winds remain out of the west this morning and have become light in speed. A slight increase in ridgetop wind speed is expected today, barley breaking the threshold to transport snow during gusts. Increasing clouds and a slight chance of snow showers returns for tomorrow. Storm totals for this past week (Tuesday night through Saturday morning) measure anywhere from 50 to 95 inches of total snow accumulation.

Observations:

Two human triggered avalanches occurred yesterday in the Mount Rose backcountry. The larger avalanche was unintentionally skier triggered on the south side of Mount Rose proper in above treeline terrain at 9,500' in a S to SE aspect gully with an estimated 35 degree slope angle. This gully was cross loaded with recent storm snow and held noticeably wind affected snow. The avalanche measured 40' wide and ran 800' down slope with a crown height of 6" to 3' deep that revealed multiple layers of recent storm snow. The skier was able to escape off the edge of the slab unharmed.

A smaller avalanche with hard slab characteristics was triggered by intentional cornice collapse on Tamarack peak in the Hourglass Bowl. This avalanche occurred in near treeline terrain at 9,840' on a N aspect portion of the open bowl with a measured 36 degree slope angle. The avalanche measured 50' wide and ran 25' down slope with a crown depth of 1'. The slab was composed of a 1 Finger hard slab of recently wind loaded snow on top of a 4 Finger hard storm snow bed surface (photos, more info).

Additional observations made yesterday on Powderhouse Peak (Luther Pass area) and in Negro Canyon (Donner Summit area) revealed widespread slab formation in all wind protected areas below treeline due to a density change within the upper portion of the storm snow and also due to wind effects in exposed near treeline areas. Minimal cracking with no significant propagation was noted as the consistent result from a variety of both formal and informal tests performed in all below treeline and near treeline areas traveled. For Powderhouse Peak pit profile, photos and more info click here. For Negro Canyon photo and more info click here.

Primary Avalanche Concern: Wind Slabs

Despite 5 to 9 inches of settlement in the past 24 hours and increasing evidence of snowpack stability, areas of unstable snow still exist. Unstable slabs of wind loaded storm snow in lee areas remain the main concern for large and potentially destructive avalanches mainly near and above treeline on NW-N-NE-E-SE-S aspects. Failure several feet deep within the recent storm snow remains possible, especially as the more recent snow near the surface gains strength and the area of relative weakness may shift deeper to other layers within the recent storm snow. Steep open areas with moderate amounts of wind effect below treeline also hold some lingering concern for slab avalanches, especially in complex or extreme terrain. Areas of instability will exist today within greater areas of seemingly stable conditions. Conservative decision making based on high quality snowpack data collection is essential for safe travel in avalanche terrain today.

The bottom line:

Near and above treeline, avalanche danger is MODERATE on recently wind loaded NW-N-NE-E-SE-S aspects 35 degrees and steeper. Isolated pockets of MODERATE danger may exist on SW-W aspects as well. Below treeline avalanche danger is LOW with pockets of MODERATE danger in open wind affected areas on all aspects, 35 degrees and steeper. Large human triggered avalanches remain possible.

Brandon Schwartz - Avalanche Forecaster, Tahoe National Forest

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

0600 temperature:	8 to 11 deg. F.
Max. temperature in the last 24 hours:	17 to 22 deg. F.
Average wind direction during the last 24 hours:	Southwest shifting to west
Average wind speed during the last 24 hours:	23 mph
Maximum wind gust in the last 24 hours:	53 mph
New snowfall in the last 24 hours:	2 to 5 inches
Total snow depth:	93 to 129 inches

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

For 7000-8000 ft:
	Sunday:	Sunday Night:	Monday:
Weather:	Partly cloudy skies.	Partly cloudy in the evening becoming mostly cloudy.	Mostly cloudy skies with a slight chance of snow showers.
Temperatures:	18 to 25 deg. F.	5 to 15 deg. F.	19 to 26 deg. F.
Wind direction:	W	SW	SW
Wind speed:	Around 10 mph.	Around 10 mph with gusts to 25 mph in the evening.	Up to 10 mph.
Expected snowfall:	O in.	O in.	0 to trace in.
For 8000-9000 ft:
	Sunday:	Sunday Night:	Monday:
Weather:	Partly cloudy skies.	Partly cloudy in the evening becoming mostly cloudy.	Mostly cloudy skies with a slight chance of snow showers.
Temperatures:	13 to 23 deg. F.	4 to 14 deg. F.	13 to 23 deg. F.
Wind direction:	W	SW	SW
Wind speed:	10 to 20 mph with gusts to 30 mph.	10 to 15 mph with gusts to 25 mph.	10 to 15 mph with gusts to 25 mph.
Expected snowfall:	O in.	O in.	0 to trace in.