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 30, 2008:


December 30, 2008 at 7:54 am

The avalanche danger is LOW for all elevations and aspects. Human triggered avalanches are unlikely but not impossible today. Isolated areas of instability may exist.


Forecast Discussion:


A high pressure ridge should bring warmer temperatures, less wind, and sunny skies to the forecast area today. The winds started to decrease overnight and have averaged about 20 mph since 6pm yesterday. By 6 am this morning the remote sensors already showed temperatures in the low 30's above 7000'.

Yesterday, observations in the Mount Rose area and on Jake's Peak continued to show a variety of snow surface conditions. On open N-NE-E aspects stiff wind affected surface snow and some hard slabs exist. Areas protected from the NE winds on those same aspects continue to hold soft, unconsolidated surface snow above 7800'. On the southerly aspects sun-crusts have formed up to at least 9000'. Snowpit tests show bonds between and within layers in the snowpack gaining strength in both of these areas. These tests also indicate continued variability in strength and distribution of the older weak layers in the snowpack. No avalanche activity was reported yesterday.

Even though dangerous avalanche activity is unlikely today, two concerns warrant extra caution because of their consequences. First, small point releases and pinwheels that may occur on southerly aspects due to daytime warming. These small, isolated instabilities should not pose much of a threat to backcountry travelers. They could be large enough to knock a person off balance. Being knocked off balance while standing in a dangerous spot like the edge of a cliff could result in serious consequences.

The second concern today is isolated hard wind slabs near and above treeline on wind affected slopes that are 37 degrees or steeper. These slabs should be hard to trigger and are unlikely to produce avalanches today. However,  there is a small chance that the right trigger in the right spot could result in a very isolated human-triggered slab avalanche. These unlikely avalanches would be a surprise to the person who triggers them due to otherwise widespread stable conditions. Use good travel habits to minimize these risks.


The bottom line:

The avalanche danger is LOW for all elevations and aspects. Human triggered avalanches are unlikely but not impossible today. Isolated areas of instability may exist.


Andy Anderson - Avalanche Forecaster, Tahoe National Forest


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

0600 temperature: 32 deg. F.
Max. temperature in the last 24 hours: 32 deg. F.
Average wind direction during the last 24 hours: Southwest
Average wind speed during the last 24 hours: 25-35 mph
Maximum wind gust in the last 24 hours: 68 mph
New snowfall in the last 24 hours: O inches
Total snow depth: 59-67 inches

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

For 7000-8000 ft:

  Tuesday: Tuesday Night: Wednesday:
Weather: Sunny Clear Partly cloudy
Temperatures: 40-46 deg. F. 28-34 deg. F. 37-42 deg. F.
Wind direction: West shifting to the southwest Southwest Southwest
Wind speed: 10 mph 10-15 mph with gusts to 25 mph 10-15 mph
Expected snowfall: O in. O in. O in.

For 8000-9000 ft:

  Tuesday: Tuesday Night: Wednesday:
Weather: Sunny Clear Partly cloudy
Temperatures: 36-44 deg. F. 27-32 deg. F. 33-38 deg. F.
Wind direction: West shifting to the southwest Southwest West
Wind speed: 10-15 mph increasing to 15-20 mph with gusts to 45 mph 15-25 mph with ridgetop gusts to 65 mph 10-20 mph with gusts to 40 mph
Expected snowfall: O in. O in. O in.