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 27, 2009:


March 27, 2009 at 6:49 am

This morning, avalanche danger is LOW for all elevations and aspects. Pockets of MODERATE danger will develop at all elevations on E-SE-S-SW-W aspects in response to daytime warming.


Forecast Discussion:


A ridge of high pressure is building over the forecast area. Maximum daytime air temperatures are expected to increase 10 to 15 degrees over yesterday's highs. Ridgetop winds remain moderate in speed out of the east this morning, but are expected to become light this afternoon through Saturday morning. A cold front is forecast to move through the area Saturday night, causing an increase in wind speeds late Saturday and cooler air temperatures on Sunday.

Yesterday, observations made at a variety of locations within the Mount Rose area matched well with recent observations from other locations within the forecast area. Stability tests indicate the presence of a stable snowpack on northerly aspects, while a melt-freeze cycle occurs on southerly aspects. Snow surface conditions are a mix of wet heavy snow, breakable crust, corn, and colder unconsolidated snow, varying by aspect and elevation. Most typical spring recreation slopes have not undergone enough melt-freeze cycles since the last storm to provide good corn conditions. Wet heavy snow and breakable crusts are found instead. Good corn snow conditions have been found in highly wind exposed areas on SW and SE aspects. Recent storm and wind events created a high density snow surface in these areas. This supportable surface is now providing supportable melt-freeze and corn snow conditions during the day. A few lingering areas of cold unconsolidated snow still exist in high elevation, below treeline areas on steep north aspects. Expect to find breakable crust on lower elevation and lower angle northerly aspects.

Last night, a strong refreeze of wet surface snow occurred at all elevations. Today, a good window for recreation will occur through the mid morning hours on all aspects and possibly into the afternoon hours on SW-W aspects. Pockets of wet snow instability are expected to form as the day progresses. Any instability that does occur is expected to remain limited to wet surface snow and not involve wet slab avalanches. This is due to the short periods of gradual warming that have occurred over the past two weeks as well as the February and March rain events that have helped to establish good melt water pathways within the snowpack. Wet loose avalanches are more difficult to human trigger than storm snow avalanches, but happen every year. If you find yourself sinking into wet snow up to the tops of your boots, it is time to move to a safer area. Switch to a more westerly or northerly aspect, or simply head for low angle slopes in order to avoid the areas of greatest danger.


The bottom line:

This morning, avalanche danger is LOW for all elevations and aspects. Pockets of MODERATE danger will develop at all elevations on E-SE-S-SW-W aspects in response to daytime warming.


Brandon Schwartz - Avalanche Forecaster, Tahoe National Forest


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

0600 temperature: 24 deg. F.
Max. temperature in the last 24 hours: 38 to 41 deg. F.
Average wind direction during the last 24 hours: East
Average wind speed during the last 24 hours: 40 mph
Maximum wind gust in the last 24 hours: 56 mph
New snowfall in the last 24 hours: O inches
Total snow depth: 146 inches

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

For 7000-8000 ft:

  Friday: Friday Night: Saturday:
Weather: Sunny skies. Clear skies. Sunny skies.
Temperatures: 43 to 50 deg. F. 33 to 38 deg. F. 49 to 54 deg. F.
Wind direction: NE NE NE shifting to SW in the afternoon.
Wind speed: Around 10 mph. Light winds. Light winds becoming 10 to 20 mph in the afternoon.
Expected snowfall: O in. O in. O in.

For 8000-9000 ft:

  Friday: Friday Night: Saturday:
Weather: Sunny skies. Clear skies. Sunny skies.
Temperatures: 39 to 45 deg. F. 30 to 35 deg. F. 44 to 50 deg. F.
Wind direction: NE NE NE shifting to W
Wind speed: 15 to 25 mph with gusts to 40 mph. Decreasing to 10 to 15 mph in the afternoon. Around 10 mph. Light winds increasing to 15 to 20 mph with gusts to 40 mph in the afternoon.
Expected snowfall: O in. O in. O in.