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 break in the weather will occur today ahead of increasing cloud cover this afternoon through tomorrow with precipitation returning to the forecast area by tomorrow evening. Near to above freezing air temperatures are expected today for areas below 9,000'. Winds have become light and variable overnight. Ridgetop winds are forecast to remain light out of the southeast this morning before shifting to the southwest and becoming light to moderate in speed this afternoon. Increasing winds overnight are expected to become moderate to strong in speed tomorrow afternoon.

Observations:

Observations made yesterday revealed a wide variance in snowpack instability ranging from active on Donner Peak and Mt. Judah (Donner Summit area) to stubbornly active along Frog Lake Ridge (Carson Pass area) to very stable on Tamarack Peak (Mount Rose area). On Donner Peak, recent natural avalanche activity from Wednesday night was visible on the NE aspect of the peak in steep near treeline terrain at around 7,800'. At 1 pm yesterday a snowboarder triggered a slab avalanche on a wind loaded NW aspect at 7,400' in near treeline terrain while approaching the slope. On Mt. Judah, natural cornice collapse had triggered several natural avalanches most likely during the early morning hours on Thursday on steep NE-E aspects near treeline. On all of these avalanches the crown depth was 12 to 14 inches deep. Snowpit data collected on Wildflower ridge between Donner Peak and Mt. Judah reveled ongoing instability within the new snow that became increasingly difficult to trigger as the day progressed (photos, videos, more info). Small warming instabilities in the form of roller balls were noted on southerly aspects in the area.

Along Frog Lake Ridge, a human triggered avalanche occurred in response to intentional cornice collapse at noon at 8,770' in near treeline terrain on a NE aspect 45 degree slope. The avalanche measured 60' wide and ran 250' down slope with an average crown depth of 1 foot and a maximum crown depth of 1.5 feet. Snowpit data collected adjacent to this avalanche revealed ongoing instability at the base of the unstable wind slab that required significant force to trigger. Good visibility of surrounding peaks in the area revealed no evidence of natural avalanche activity (photos, pit profile, more info).

On Tamarack Peak no evidence of instability was observed. Snowpit data collected from a variety of near treeline locations on NE-E aspects between 9,800' and 9,900' revealed rough shear quality and unlikely fracture within the new snow. Good bonding was observed at the old/new snow interface. Cornice collapse failed to produce any signs of slab instability. By 11 am, settlement cones around trees on N aspects revealed 3+ inches of settlement within the new snow. No evidence of avalanche activity of any type was visible in the area (photos, more info).

Avalanche Concern #1: Warming instability

Near to above freezing air temperatures below 9,000' combined with March levels of solar radiation will cause some warming instability today. Most of the warming instability is expected to take the form of roller balls and point release loose snow avalanches with minimal hazard to backcountry travelers. Cross loaded S-SE aspect gullies and other recently wind loaded southerly aspects will hold the greatest opportunity for human triggered slab avalanches of significant hazard to backcountry travelers to occur under the influence of warming.

Avalanche Concern #2: Storm snow and wind slabs

Lingering instability of storm snow and wind slabs in the upper portion of the snowpack remains an ongoing concern. Slab avalanche activity on NW-N-NE-E aspects near and above treeline is expected to be more difficult to trigger today and may require larger triggers such as cornice collapse or multiple persons on a slope at one time. Any slab avalanche activity that occurs today on NW-N-NE-E aspects will most likely be fairly isolated and limited to the top 1 to 2 feet of the snowpack.

The bottom line:

Near and above treeline, areas of MODERATE danger will form today on SE-S-SW aspects on slopes 37 degrees and steeper in response to daytime warming. Pockets of MODERATE danger exist near and above treeline on NW-N-NE-E aspects 35 degrees and steeper due to lingering storm snow instabilities. Below treeline areas of MODERATE danger will form today on SE-S-SW aspects on slopes 37 degrees and steeper in response to daytime warming. Elsewhere, avalanche danger is LOW.

Brandon Schwartz - Avalanche Forecaster, Tahoe National Forest

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

0600 temperature:	16 to 22 deg. F.
Max. temperature in the last 24 hours:	25 to 32 deg. F.
Average wind direction during the last 24 hours:	Southwest
Average wind speed during the last 24 hours:	21 mph
Maximum wind gust in the last 24 hours:	55 mph
New snowfall in the last 24 hours:	0 to trace inches
Total snow depth:	94 to 135 inches

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

For 7000-8000 ft:
	Friday:	Friday Night:	Saturday:
Weather:	Sunny skies in the morning with increasing high clouds through the afternoon.	Mostly cloudy skies.	Cloudy skies with a slight chance of snow in the afternoon.
Temperatures:	34 to 40 deg. F.	21 to 27 deg. F.	36 to 42 deg. F.
Wind direction:	SE shifting to SW	SW	SW
Wind speed:	Calm in the morning increasing to up to 10 mph.	Up to 10 mph.	10 to 15 mph.
Expected snowfall:	O in.	O in.	0 to trace in.
For 8000-9000 ft:
	Friday:	Friday Night:	Saturday:
Weather:	Sunny skies in the morning with increasing high clouds through the afternoon.	Mostly cloudy skies.	Cloudy skies with a slight chance of snow in the afternoon.
Temperatures:	28 to 34 deg. F.	Around 20 deg. F.	28 to 36 deg. F.
Wind direction:	SE shifting to SW	SW	SW
Wind speed:	Around 10 mph in the morning shifting and increasing to 10 to 20 mph with gusts to 30 mph in the afternoon.	15 to 30 mph with gusts to 40 mph.	20 to 30 mph with gusts to 45 mph. Winds increasing to 25 to 35 mph with gusts to 60 mph in the afternoon.
Expected snowfall:	O in.	O in.	0 to trace in.