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 March 14, 2009:


March 14, 2009 at 7:00 am

Avalanche danger is LOW for all elevations and aspects. LOW danger does not mean no danger. Continue to use safe travel habits and evaluate slopes carefully before weighting them.


Forecast Discussion:


The winds have shifted to the southwest and increased overnight as a low-pressure system begins to affect the forecast area. These winds should continue through out the storm. Cloud cover also moved in overnight. This storm should bring a chance for snow starting tonight and continuing through Monday afternoon. The Sierra Crest west of the lake should see most of the accumulation. The Carson Range east of the lake should see much less snow due to the rain shadow effect.

Observations from across the forecast area this week have shown a strengthening snowpack with a mix of snow surface conditions depending on aspect and elevation. Cold, soft powder still exists on N-NE aspects above 7000' that have been protected from the wind and sun. On E-SE-S-SW-W aspects, the sun and warm temperatures have started a melt-freeze cycle. For a few hours during the afternoon 1-3 inches of soft wet snow exists on these aspects up to about 8500'. The clear, cold nights allow this wet surface snow to re-freeze leaving a hard icy surface on these aspects in the mornings. Breakable crusts, and supportable crusts exist on many E and NW aspects. Above treeline hard, wind-packed surfaces and hard, wind-scoured surfaces exist on almost all aspects that were exposed to the winds during the last storm.

Today cloud cover will allow snow on the northerly aspects to experience some warming during the day. Small, human-triggerable wet-snow instabilities like point releases, pin-wheels, or roller-balls could form on these aspects. These surface instabilities could also form on SE-S-SW slopes if the sun hits them today. Without direct sunshine these aspects may remain more frozen today. The gradual warming and strong overnight refreezes should prevent large wet-snow instabilities from forming today. Remember LOW avalanche danger does not mean no avalanche danger. Even though the snowpack is generally stable and avalanches are unlikely, some small, isolated areas of unstable snow could still exist. Expect the avalanche danger to rise over the next 24 hours as wind and new snow impact the forecast area. Use good travel habits to minimize risks.


The bottom line:

Avalanche danger is LOW for all elevations and aspects. LOW danger does not mean no danger. Continue to use safe travel habits and evaluate slopes carefully before weighting them.


Andy Anderson - Avalanche Forecaster, Tahoe National Forest


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

0600 temperature: 26 deg. F.
Max. temperature in the last 24 hours: 46-49 deg. F.
Average wind direction during the last 24 hours: East shifting to the southwest
Average wind speed during the last 24 hours: 20 mph
Maximum wind gust in the last 24 hours: 45 mph
New snowfall in the last 24 hours: O inches
Total snow depth: 144 inches

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

For 7000-8000 ft:

  Saturday: Saturday Night: Sunday:
Weather: Mostly cloudy Cloudy with isolated snow showers Mostly cloudy with snow showers. Most accumulation should occur over the Sierra Crest west of the lake. Snow level 6500 ft.
Temperatures: 40-46 deg. F. 22-29 deg. F. 39-45 deg. F.
Wind direction: Southwest Southwest Southwest
Wind speed: 10-15 mph increasing to 15-25 mph with gusts to 35 mph 20-30 mph with gusts to 45 mph 20-30 mph with gusts to 50 mph
Expected snowfall: O in. up to 1 in. 2-5 in.

For 8000-9000 ft:

  Saturday: Saturday Night: Sunday:
Weather: Mostly cloudy Cloudy with isolated snow showers Mostly cloudy with snow showers. Most accumulation should occur over the Sierra Crest west of the lake.
Temperatures: 35-41 deg. F. 19-26 deg. F. 34-40 deg. F.
Wind direction: Southwest West Southwest
Wind speed: 20-30 mph with gusts to 50 mph 30-45 mph with gusts to 70 mph 30-50 mph with gusts to 80 mph increasing to 100 mph along the ridgetops
Expected snowfall: O in. up to 2 in. 3-6 in.