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 26, 2008:


December 26, 2008 at 7:52 am

Near and above treeline, avalanche danger is MODERATE on all aspects, 35 degrees and steeper. Below treeline, avalanche danger is LOW with pockets of MODERATE danger in open areas 37 degrees and steeper.


Forecast Discussion:


The storm that affected the forecast area for the past few days has moved off to the east. New snowfall in the past 24 hours measures 5 to 10 inches. Storm totals for the period 12/24 - 12/26 are running around 26 to 38 inches along the Sierra Crest and 18 to 24 inches in the Mount Rose area. Ridgetop winds were very strong and shifted from the southwest to northwest during the storm. Overnight, winds have become light and have shifted to the northeast this morning. Ridgetop winds are expected to increase to moderate in speed by this afternoon. Air temperatures this morning are in the single digits in most areas and are not expected to warm beyond the lower teens today at the upper elevations.

Yesterday, we were unable to make any backcountry observations. Alpine Meadows ski patrol reported very active avalanche control work within the ski area. The Mt. Rose ski patrol reported some slab formation within the ski area and human triggered avalanches occurred within the new snow on an inconsistent basis. This evidence indicates that human triggered avalanches were possible in the backcountry with slab failure possible within the new snow in near and above treeline areas. We will resume backcountry observations today.

Today in the backcountry, existing slabs are expected to remain and new slabs will form. As northeast winds begin to redistribute snow, areas that were wind loaded during the past few days will become somewhat but not completely scoured. Human triggered avalanches are expected to remain possible within the storm snow or at or near the interface between the storm snow and the older snow layer below it. Additionally, northeast winds will cause new wind loading in lee areas, creating new slabs and the possibility of human triggered avalanches on all aspects today. Due to the lack of backcountry observations from yesterday, confidence for this advisory is slightly below normal.


The bottom line:

Near and above treeline, avalanche danger is MODERATE on all aspects, 35 degrees and steeper. Below treeline, avalanche danger is LOW with pockets of MODERATE danger in open areas 37 degrees and steeper.


Brandon Schwartz - Avalanche Forecaster, Tahoe National Forest


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

0600 temperature: 4 deg. F.
Max. temperature in the last 24 hours: 18 deg. F.
Average wind direction during the last 24 hours: Southwest clocking to northeast.
Average wind speed during the last 24 hours: 50 mph
Maximum wind gust in the last 24 hours: 113 mph
New snowfall in the last 24 hours: 5 to 10 inches
Total snow depth: 55 to 65 inches

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

For 7000-8000 ft:

  Friday: Friday Night: Saturday:
Weather: Partly cloudy skies. Cloudy skies. Cloudy skies with a slight chance of snow showers.
Temperatures: 12 to 19 deg. F. 11 to 17 deg. F. 27 to 34 deg. F.
Wind direction: Northeast Variable, becoming southwest. West
Wind speed: Around 10 mph Up to 10 mph. Up to 10 mph.
Expected snowfall: O in. O in. 0 to trace in.

For 8000-9000 ft:

  Friday: Friday Night: Saturday:
Weather: Partly cloudy skies. Mostly cloudy skies. Mostly cloudy with a slight chance of snow showers.
Temperatures: 9 to 15 deg. F. 9 to 15 deg. F. 25 to 32 deg. F.
Wind direction: Northeast Northeast shifting to west after midnight. Northwest
Wind speed: 10 to 15 mph with gusts to 25 mph 5 to 15 mph with gusts to 30 mph. 10 to 15 mph with gusts to 25 mph, increasing to 35 mph in the afternoon.
Expected snowfall: O in. O in. 0 to trace in.