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 February 5, 2012:


February 5, 2012 at 8:00 am

Avalanche danger remains LOW for all elevations and aspects. Use normal caution when traveling in the backcountry.


Forecast Discussion:


The high pressure ridge over the forecast area will allow sunny skies and light easterly winds to prevail again today. Temperatures should remain similar to the last few days with highs in the low 30's to low 40's above 7000 ft today. By tomorrow this ridge should start to move eastward allowing some clouds to start forming over the region ahead of a small low pressure system. The winds should also shift towards the south tomorrow afternoon and slowly start to increase.

Recent Observations:

Yesterday in the Silver Peak area (pit profile, more info), light east winds and relatively cool daytime highs prevented much softening from occurring on even the sun-exposed SE-S-SW aspects. By 1pm less than an inch of soft melt-freeze snow existed on lower elevation SW aspects in areas sheltered from the wind. The snowpack on these southerly aspects consists mostly of this melt-freeze snow and strong well consolidated snow below it. On aspects facing the northerly half of the compass, a thin breakable rain crust caps the snowpack in most areas. A few slopes still have patches new snow on top of this crust, but in most areas the N-NE-E winds that occurred after the recent storm scoured this new snow away. The recent weather has allowed a weak layer of sugary snow grains (facets) to form underneath the rain crust. This same faceting process continues to erode the rain crust slowly making it thinner and weaker. Below these surface layers, snowpack data showed a strong and mostly stable snowpack in the Silver Peak area yesterday. Observations across the forecast area this week have shown similar conditions with melt-freeze conditions on the southerly aspects and breakable crusts and near surface facets on the northerly aspects.

Today's Avalanche Concerns:

Avalanche activity should remain unlikely again today. Even though recent observations have shown a weak layer forming on the NW-N-NE aspects, no slab layer exists on top of this weak layer. Today's weather conditions will not create any new slab layers on top of these weak layers keeping avalanches improbable on these slopes. On the more sun-exposed SE-S-SW aspects, the freezing part of the melt-freeze cycle has lasted much longer than the melting part of this cycle with only a brief period of melting occurring on the wind-sheltered slopes yesterday afternoon. Any wet snow that did form should have refrozen last night. Weather conditions similar to yesterday should prevent significant melting from occurring again today. Due to this lack of melting, wet snow instabilities should remain rare, isolated, and small if they form at all today. 


The bottom line:

Avalanche danger remains LOW for all elevations and aspects. Use normal caution when traveling in the backcountry.


Andy Anderson - Avalanche Forecaster, Tahoe National Forest


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

0600 temperature: 17-25 deg. F.
Max. temperature in the last 24 hours: 27-36 deg. F.
Average wind direction during the last 24 hours: East
Average wind speed during the last 24 hours: 10-15 mph
Maximum wind gust in the last 24 hours: 31 mph
New snowfall in the last 24 hours: O inches
Total snow depth: 19-36 inches

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

For 7000-8000 ft:

  Sunday: Sunday Night: Monday:
Weather: Sunny Clear Partly cloudy
Temperatures: 36-43 deg. F. 19-27 deg. F. 37-44 deg. F.
Wind direction: Southeast East Variable
Wind speed: 10-15 mph with gusts to 25 mph 10-15 mph with gusts to 25 mph becoming light during the night Light
Expected snowfall: O in. O in. O in.

For 8000-9000 ft:

  Sunday: Sunday Night: Monday:
Weather: Sunny Clear Partly cloudy
Temperatures: 31-41 deg. F. 21-31 deg. F. 31-41 deg. F.
Wind direction: Southeast Southeast South
Wind speed: 10-15 mph with gusts to 25 mph 15-20 mph with gusts to 30 mph becoming light during the night 10-15 mph with gusts to 25 mph in the afternoon
Expected snowfall: O in. O in. O in.