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 December 23, 2008:


December 23, 2008 at 8:03 am

Near and above treeline the avalanche danger is MODERATE with pockets of CONSIDERABLE on NW-N-NE-E-SE slopes steeper than 35 degrees. Below treeline the avalanche danger is LOW with pockets of MODERATE on open slopes steeper than 35 degrees.


Forecast Discussion:


Overnight 6 to 10 inches of new snow fell across the forecast area. A small ridge of high pressure moving into the area should bring some short term clearing today. Two more back to back low pressure systems should begin affecting the forecast area tonight with increasing southwest winds. These systems should be warmer and more moist than the last few storms. The forecast calls for snow levels to rise slightly on Wednesday before dropping again by Thursday. These two systems could produce 18 to 24 inches of snow above 7000' by Thursday afternoon.

Yesterday, avalanche activity occurred on steep wind loaded slopes along the Sierra Crest near and above treeline as a result of large triggers. Skiers produced small avalanches on steep test slopes in the Silver Peak area below treeline but could not cause failure on similar slopes above treeline. The test slope failure occurred on the interface between the two most recent storms.  Observations in the Mount Rose area showed less avalanche activity and smaller avalanches due to less snow and wind loading. Observations indicate that a variety of weak layers and slabs exist across the forecast area.

Overnight and through today, human triggered avalanche will remain possible below treeline and will be probable near and above treeline on steep wind loaded slopes. Some natural avalanche activity may still be possible on the most heavily wind loaded slopes near and above treeline.  NW-N-NE-E-SE aspects should have the most new wind loading and should be the most prone to avalanche activity today. Most avalanches should fail on the interface between the two most recent storms; however, large avalanches resulting from failure of an older weak layer are still possible today and would have serious consequences.


The bottom line:

Near and above treeline the avalanche danger is MODERATE with pockets of CONSIDERABLE on NW-N-NE-E-SE slopes steeper than 35 degrees. Below treeline the avalanche danger is LOW with pockets of MODERATE on open slopes steeper than 35 degrees.


Andy Anderson - Avalanche Forecaster, Tahoe National Forest


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

0600 temperature: 15 deg. F.
Max. temperature in the last 24 hours: 19 deg. F.
Average wind direction during the last 24 hours: Southwest
Average wind speed during the last 24 hours: 35-45 mph
Maximum wind gust in the last 24 hours: 74 mph
New snowfall in the last 24 hours: 8-10 inches
Total snow depth: 50 inches

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

For 7000-8000 ft:

  Tuesday: Tuesday Night: Wednesday:
Weather: Mostly cloudy with scattered snow showers in the morning. Isolated snow showers in the afternoon. Cloudy with chance of snow. Snow.
Temperatures: 20-27 deg. F. 10-17 deg. F. 23-30 deg. F.
Wind direction: West Southwest Southwest
Wind speed: 10-15 mph with gusts to 25 mph. 10-15 mph. 10 to 15 mph in the morning increasing to 15 to 25 mph with gusts to 45 mph in the afternoon.
Expected snowfall: up to 1 in. up to 1 in. 3-6 in.

For 8000-9000 ft:

  Tuesday: Tuesday Night: Wednesday:
Weather: Mostly cloudy with scattered snow showers in the morning. Isolated snow showers in the afternoon. Cloudy with chance of snow. Snow.
Temperatures: 12-19 deg. F. 11-17 deg. F. 20-27 deg. F.
Wind direction: West Southwest Southwest
Wind speed: 20-30 mph with gusts to 50 mph decreasing to 10-20 mph with gusts to 30 mph in the afternoon. 15-20 mph with gusts to 40 mph. 25-40 mph with gusts to 60 mph increasing to 40-55 mph with gusts to 90 mph in the afternoon.
Expected snowfall: up to 1 in. up to 2 in. 4-8 in.