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 6, 2012:


December 6, 2012 at 8:04 am

Above 9000 ft in near and above treeline terrain, MODERATE avalanche danger may linger on pockets of NW-N-NE-E aspects on slopes steeper than 35 degrees due to wind slabs. For all other areas, avalanche danger is LOW.


Forecast Discussion:


After depositing another .4-1 inch of rain on the snowpack below 9000 ft and only a few inches of snow above 9000 ft, the storm has departed the area. Skies should become mostly sunny today, and the winds should remain moderate. Over the next 24 hours, the winds should begin shifting to the north and east as a high pressure ridge builds over the region. This ridge should bring mostly clear skies and cooler temperatures to the forecast area today, tonight, and tomorrow.

Recent Observations:

Several natural and human triggered wet loose sluffs released on Elephant's Back (photos, video, more info) and on Incline Lake Peak (photos, snowpit, more info) yesterday. Snowpits in these areas showed that rain had saturated the upper snowpack creating a 10-20 cm deep layer of wet snow and slush below 9000ft. The rain had already broken many of the cornices near Elephant's Back. Above 9000 ft on Incline Lake Peak, the recent precipitation was mostly snow. Tests showed good bonding between this snow and the layers below it. Oven to refrigerator sized cornice pieces dropped onto steep wind loaded test slopes did not result in any slope fractures.

Today's Primary Avalanche Concern: Wind Slabs

New wind slabs that formed during the storm still exist on NW-N-NE-E aspects in near and above treeline terrain above 9000 ft. Most of these slabs should have bonded well to the snowpack below them and triggering them should be difficult today. However, some areas where human triggered avalanches remain possible may still exist especially in wind loaded complex or extreme terrain.

Other things to think about:

Some sluffing may still occur today below 9000 ft. As the water in the snowpack refreezes, the snowpack should grow stronger and more stable.This process will take several days due to the insulating properties of snow. Continue to use normal caution when traveling in the backcountry.


The bottom line:

Above 9000 ft in near and above treeline terrain, MODERATE avalanche danger may linger on pockets of NW-N-NE-E aspects on slopes steeper than 35 degrees due to wind slabs. For all other areas, avalanche danger is LOW.


Andy Anderson - Avalanche Forecaster, Tahoe National Forest


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

0600 temperature: 27-32 deg. F.
Max. temperature in the last 24 hours: 34-40 deg. F.
Average wind direction during the last 24 hours: West Southwest
Average wind speed during the last 24 hours: 20 mph
Maximum wind gust in the last 24 hours: 55 mph
New snowfall in the last 24 hours: rain up to 9000 ft of .4-1 inches
Total snow depth: 35-56 inches

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

For 7000-8000 ft:

  Thursday: Thursday Night: Friday:
Weather: Sunny then becoming partly cloudy. Clear becoming partly cloudy Partly cloudy
Temperatures: 36-43 deg. F. 20-27 deg. F. 34-41 deg. F.
Wind direction: West West shifting to the northeast after midnight Northeast
Wind speed: 10-15 mph with gusts to 25 mph 15-20 mph 10-15 mph with gusts to 25 mph
Expected snowfall: O in. O in. O in.

For 8000-9000 ft:

  Thursday: Thursday Night: Friday:
Weather: Sunny then becoming partly cloudy. Clear becoming partly cloudy Partly cloudy
Temperatures: 33-40 deg. F. 21-28 deg. F. 32-39 deg. F.
Wind direction: West Northwest shifting to the northeast after midnight Northeast
Wind speed: 15-25 mph with gusts to 35-40 mph 20-30 mph with gusts to 45-50 mph 15-25 mph with gusts to 40 mph
Expected snowfall: O in. O in. O in.

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