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 January 5, 2009:


January 5, 2009 at 8:00 am

This morning the avalanche danger is LOW for all elevations and aspects. Some small, isolated pockets of MODERATE danger may develop near and above treeline on N-NE-E aspects steeper than 37 degrees by this afternoon.


Forecast Discussion:


A small storm system moving southeast from the Pacific Northwest will bring increased westerly winds and some snow to the forecast area today. The winds started to increase overnight and have averaged between 55 and 60 mph since 2 am this morning. The snow showers that started this morning should only add another 1 inch of accumulation before tapering off this afternoon. As this storm moves east the winds should decrease and shift to the northwest by tomorrow.

Yesterday, layer bonding tests on Castle Peak indicated that the bond between the January 2nd rain crust and the snow above it has gained some strength. However, observations and snowpit data showed that facets continue to form near this crust. The clear and cold weather over the last two days has caused the snow surface temperatures to remain much colder than the temperatures 12 inches below the surface of the snow. This large difference in temperatures promotes the growth of weak faceted snow. As temperatures start to warm up the faceting near the rain crust should slow down. Tests on the deeper weak layers near the bottom of the snowpack indicate that these once faceted snow grains are starting to round and gain strength. Observations from Hidden Peak and Rubicon Peak from January 3rd show similar trends.

Today, the wind and new snow will only add minor loading to the snowpack. The current snowpack should be strong enough to handle this new load in most places. In areas that have more well developed facets near the January 2nd rain crust and receive more intense wind loading, some isolated pockets of instability may develop by this afternoon. These pockets would be most likely found on steep wind loaded N-NE-E aspects near and above treeline.  Any avalanches that occur in these areas would likely only involve the snow above the January 2nd rain crust.


The bottom line:

This morning the avalanche danger is LOW for all elevations and aspects. Some small, isolated pockets of MODERATE danger may develop near and above treeline on N-NE-E aspects steeper than 37 degrees by this afternoon.


Andy Anderson - Avalanche Forecaster, Tahoe National Forest


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

0600 temperature: 17 deg. F.
Max. temperature in the last 24 hours: 24 deg. F.
Average wind direction during the last 24 hours: West southwest
Average wind speed during the last 24 hours: 10 mph until 6 pm last night then 35 mph
Maximum wind gust in the last 24 hours: 71 mph
New snowfall in the last 24 hours: 0-.1 inches
Total snow depth: 64 inches

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

For 7000-8000 ft:

  Monday: Monday Night: Tuesday:
Weather: Cloudy with a snow showers in the morning. Snow showers decreasing and becoming scattered this afternoon. Mostly cloudy Mostly cloudy
Temperatures: 35-41 deg. F. 19-26 deg. F. 38-45 deg. F.
Wind direction: West West Northwest
Wind speed: 10-20 mph with gusts to 35 mph 10 mph with gusts to 25 mph 10 mph
Expected snowfall: 0-1 in. O in. O in.

For 8000-9000 ft:

  Monday: Monday Night: Tuesday:
Weather: Cloudy with a snow showers in the morning. Snow showers decreasing and becoming scattered this afternoon. Mostly cloudy Mostly cloudy
Temperatures: 28-35 deg. F. 20-27 deg. F. 36-43 deg. F.
Wind direction: West Northwest Northwest
Wind speed: 30-45 with gusts to 70 mph 30-40 mph with gusts to 70 mph 20-35 mph with gusts to 60 mph
Expected snowfall: 0-1 in. O in. O in.