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.


This Avalanche Advisory was published on February 8, 2009:


February 8, 2009 at 7:54 am

Near and above treeline, pockets of MODERATE avalanche danger exist on all aspects, 37 degrees and steeper. Below treeline, avalanche danger is LOW.


Forecast Discussion:


Changing weather is forecast for today as another storm system approaches the forecast area with precipitation expected to begin late today. Sunny skies this morning will give way to increasing cloud cover as the day progresses. Ridgetop winds are shifting from NE to SW this morning ahead of the approaching storm system.

Yesterday, moderate to strong NE winds transported significant amounts of snow in near and above treeline areas. Evidence of snowpack instability was highly limited to human triggering. Observations made in Horse Canyon and Poison Canyon (Bear Valley/Ebbetts Pass area) showed significant scouring of snow from N-NE-E aspects and unstable slab formation on wind loaded SW-W-NW aspects. Skier triggered shooting cracks were common in wind loaded areas. Actual test slope slab failure occurred less frequently and only on slopes steeper than 40 degrees. On Barker Peak (Echo Summit area), small skier triggered slab avalanches were reported in steep wind affected areas on northerly aspects near and above treeline. These small avalanches were not large enough to bury a person. On Ellis Peak (Blackwood Canyon/Tahoe Basin area), some weakness was reported within the new snow, but no shooting cracks or test slope failure was observed in near and below treeline areas.

Today, small slabs will linger near and above treeline in steep wind loaded areas. Slabs that formed yesterday on SW-W-NW aspects will remain this morning. As SW ridgetop winds increase today, some wind scouring will occur on these aspects, with the most significant reduction in slab depth occurring on SW and W aspects. On NW-N-NE-E aspects, areas of instability that existed yesterday, especially near treeline will linger today. NW aspects that hold more snow and have been consistently cross loaded over the past two days are highly suspect. Overall slab size is expected to remain small with any failure occurring within the new snow.


The bottom line:

Near and above treeline, pockets of MODERATE avalanche danger exist on all aspects, 37 degrees and steeper. Below treeline, 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: 23 deg. F.
Max. temperature in the last 24 hours: 29 deg. F.
Average wind direction during the last 24 hours: NE shifting to SW early this morning.
Average wind speed during the last 24 hours: 45 mph
Maximum wind gust in the last 24 hours: 64 mph
New snowfall in the last 24 hours: O inches
Total snow depth: 70 inches

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

For 7000-8000 ft:

  Sunday: Sunday Night: Monday:
Weather: Increasing clouds with a slight chance of snow in the afternoon. Cloudy skies with snow. Cloudy skies with snow showers likely in the morning. A chance of snow showers in the afternoon.
Temperatures: 28 to 35 deg. F. 12 to 19 deg. F. 15 to 22 deg. F.
Wind direction: SW SW W
Wind speed: 10 to 15 mph with gusts up to 35 mph in the afternoon. 20 to 30 mph with gusts to 50 mph. 15 to 20 mph with gusts to 35 mph.
Expected snowfall: 0 to trace in. 3 to 6 in. 1 to 2 in.

For 8000-9000 ft:

  Sunday: Sunday Night: Monday:
Weather: Increasing clouds with a slight chance of snow in the afternoon. Cloudy skies with snow. Cloudy skies with snow showers likely in the morning. A chance of snow showers in the afternoon.
Temperatures: 24 to 31 deg. F. 7 to 14 deg. F. 10 to 17 deg. F.
Wind direction: SW SW W
Wind speed: 10 to 15 mph with gusts to 40 mph. Increasing to 25 to 35 mph with gusts to 65 mph in the afternoon. 30 to 50 mph with gusts to 85 mph. 20 to 35 mph with gusts to 55 mph.
Expected snowfall: 0 to trace in. 4 to 8 in. 1 to 2 in.