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 17, 2009:


January 17, 2009 at 7:59 am

The avalanche danger remains LOW for all elevations and aspects. Use normal caution when travelling in the backcountry.


Forecast Discussion:


The strong high pressure ridge over the west coast will cause the spring-like weather to remain over the forecast area. Most of the remote sensors already show temperatures in the mid to upper 30's this morning. Today's highs should rise into the low to mid 40's at all elevations. The easterly winds should continue through tonight. Gusts along the Sierra ridges could reach into the 50 mph range again today. Overnight lows should drop below freezing. By tomorrow the winds should shift more to the south as the high pressure finally starts to move to the east.

Snowpit data and observations from across the forecast area show a generally strong and stable snowpack. Breakable crusts, supportable crusts, and wind affected snow exist on the the surface in most areas. The upper few inches of snow has started to recrystallize into facets on some of the northerly aspects. Snowpit tests show that the older, persistent weak layers near the base of the snowpack have gained strength during this prolonged high pressure. Melt-freeze conditions exist on southerly aspects where 1 to 3 inches of surface snow consistently softens for a few hours around midday. Unfortunately, several areas of rocks and dirt exist on these southerly aspects due to the thin snow cover. The areas of soft, melt-freeze snow quickly refreeze as soon as they lose direct sun each day. Overnight the snowpack continues to freeze even when the temperatures remain above freezing due to radiational cooling.

This melt-freeze cycle will continue as long as the spring-like weather remains. The weak January sun, cool easterly winds, and strong overnight refreezes will keep wet snow instabilities from forming again today. The softening and melting that occurs today should be limited to the top few inches of snow on southerly sun-exposed aspects. This snow will quickly refreeze once it is shaded. All avalanche activity will remain unlikely today.


The bottom line:

The avalanche danger remains LOW for all elevations and aspects. Use normal caution when travelling 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: 35 deg. F.
Max. temperature in the last 24 hours: 45 deg. F.
Average wind direction during the last 24 hours: East northeast
Average wind speed during the last 24 hours: 35 mph
Maximum wind gust in the last 24 hours: 52 mph
New snowfall in the last 24 hours: O inches
Total snow depth: 59 inches

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

For 7000-8000 ft:

  Saturday: Saturday Night: Sunday:
Weather: Sunny Clear Sunny
Temperatures: 42-49 deg. F. 21-31 deg. F. 40-47 deg. F.
Wind direction: Northeast East Southeast
Wind speed: 10 mph with gusts to 25 mph 10 mph with gusts to 25 mph 10 mph
Expected snowfall: O in. O in. O in.

For 8000-9000 ft:

  Saturday: Saturday Night: Sunday:
Weather: Sunny Clear Sunny
Temperatures: 39-46 deg. F. 25-31 deg. F. 37-44 deg. F.
Wind direction: Northeast East South shifting to the southeast in the afternoon
Wind speed: 20-30 mph with gusts to 50 mph 15-25 mph with gusts to 40 mph 15-25 mph with gusts to 40 mph decreasing to 10-15 mph with gusts to 25 mph in the afternoon
Expected snowfall: O in. O in. O in.