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 11, 2009:


January 11, 2009 at 8:02 am

Avalanche danger is LOW for all elevations and aspects. Normal caution is advised.


Forecast Discussion:


A strong high pressure ridge over the west coast will bring sunny, spring-like weather to the forecast area for the next several days. Expect to see daytime highs in the low to mid 50's and overnight lows around freezing. Moderate, cool east to northeast winds should continue until the high pressure starts to move east later this week.

Observations across the forecast area show a variety of wind affected snow, melt-freeze snow, supportable crusts, and breakable crusts on the surface in most areas. Some pockets of unconsolidated snow exist on higher elevation northerly aspects that are protected from wind and sun. The surface snow that melted and softened yesterday should have refrozen last night due to radiational cooling and below freezing temperatures. Snowpits continue to show some persistent weak layers within the snowpack ranging from facets around some of the crusts to pockets of depth hoar in areas that had snow cover before the December storms. The strength and distribution of these weak layers varies greatly across the forecast area and even across a slope. Right now avalanche activity should remain unlikely on these layers for two reasons. One, strong well-bonded snow sits on top of the depth hoar and should have enough strength to hold itself up. Two, the facets that have formed near some of the upper crusts only have 1 to 3 inches of snow on top of them. The current weather should allow these weak layers to consolidate and gain more strength before the next storm cycle.

Today warmer air temperatures and sun should quickly melt and soften the snow surface on southerly aspects. This cycle of melting during the day and freezing overnight will continue as long as the current high pressure system affects the forecast area. The cool, east winds and the low-intensity January sunshine combined with the prolonged melt-freeze cycle should keep wet snow instabilities small today.

 


The bottom line:

Avalanche danger is LOW for all elevations and aspects. Normal caution is advised.


Andy Anderson - Avalanche Forecaster, Tahoe National Forest


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

0600 temperature: 34 deg. F.
Max. temperature in the last 24 hours: 43 deg. F.
Average wind direction during the last 24 hours: Northeast to east
Average wind speed during the last 24 hours: 25-30 mph
Maximum wind gust in the last 24 hours: 55 mph
New snowfall in the last 24 hours: O inches
Total snow depth: 62 inches

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

For 7000-8000 ft:

  Sunday: Sunday Night: Monday:
Weather: Sunny Clear Sunny
Temperatures: 50-58 deg. F. 32-42 deg. F. 50-58 deg. F.
Wind direction: North East East
Wind speed: 10 mph decreasing in the afternoon 10 mph 10-25 mph with gusts to 40 mph
Expected snowfall: O in. O in. O in.

For 8000-9000 ft:

  Sunday: Sunday Night: Monday:
Weather: Sunny Clear Sunny
Temperatures: 45-53 deg. F. 35-43 deg. F. 47-55 deg. F.
Wind direction: North Northeast Northeast
Wind speed: 25-40 mph with gusts to 60 mph 25-40 mph with gusts to 60 mph 30-50 mph with gusts to 70 mph decreasing to 20-30 mph with gusts to 50 mph in the afternoon
Expected snowfall: O in. O in. O in.