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 6, 2012:


January 6, 2012 at 8:00 am

LOW avalanche danger exists for all elevations and aspects. Use normal caution in the backcountry.


Forecast Discussion:


A low pressure system passing through the Pacific Northwest should allow some clouds to form over the forecast area this afternoon and tonight. The winds should also increase as this system brushes past. The forecast does not call for any precipitation to accompany these clouds. After another day of above average temperatures today (mid 40's above 7000 ft), the daytime highs should cool off into the low 30's tomorrow, and the winds should shift to the north and northeast as the low pressure moves farther east of the region.

Observations:

Yesterday observations above Five Lakes showed between 4 and 10 inches of snow sitting on top of a solid mass of ice above 7000 ft on the northerly aspects. In the shallow areas, the rain and warm temperatures had destroyed all of the weak facets that used to exist in the snowpack leaving behind a thick  and frozen rain / melt-freeze crust. In the deeper areas, some facets remained underneath a two to three inch rain crust. These leftover facets had icy bonds connecting them, and the snowpit data and stability tests indicated that they continue to strengthen. Observations since the rain event on Dec. 28-29 across the forecast areas have shown a mostly stable snowpack that continues to gain strength. In the areas where less rain fell (mostly south of Barker Pass and on the east side of the Lake), some weaker facets still remain underneath the rain / melt freeze surface crusts. Luckily less snow exists, and more anchors protrude through the snowpack in these areas. Above 9000 ft where less rain and warming have occurred strong north and easterly winds earlier this fall and winter have scoured most of the snow away from these once worrisome starting zones.

Avalanche Concerns:

Avalanche activity remains unlikely. The spring-like weather has allowed the once persistent weak layer to gain strength in most of the areas where it could have posed a problem. In the areas it still remains, anchors abound. Those anchors disrupt the remaining facets and hold the snowpack in place. Even though the avalanche danger remains low, plenty of other hazards like icy slopes with rocks and trees at the bottom exist. Continue to use caution when traveling in the backcountry.


The bottom line:

LOW avalanche danger exists for all elevations and aspects. Use normal caution 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: 33-36 deg. F.
Max. temperature in the last 24 hours: 44-48 deg. F.
Average wind direction during the last 24 hours: Southwest
Average wind speed during the last 24 hours: 20-25 mph
Maximum wind gust in the last 24 hours: 39 mph
New snowfall in the last 24 hours: O inches
Total snow depth: 0-18 inches

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

For 7000-8000 ft:

  Friday: Friday Night: Saturday:
Weather: Sunny in the morning becoming partly cloudy this afternoon Partly cloudy Partly cloudy in the morning becoming sunny in the afternoon
Temperatures: 41-46 deg. F. 20-27 deg. F. 32-38 deg. F.
Wind direction: West West to northwest North shifting to the northeast in the afternoon
Wind speed: 5-15 mph 10-15 mph with gusts to 35 mph after midninght 10-15 mph with gusts to 35 mph
Expected snowfall: O in. O in. O in.

For 8000-9000 ft:

  Friday: Friday Night: Saturday:
Weather: Sunny in the morning becoming partly cloudy this afternoon Partly cloudy Partly cloudy in the morning becoming sunny in the afternoon
Temperatures: 36-42 deg. F. 19-25 deg. F. 26-32 deg. F.
Wind direction: West Northwest North shifting to the northeast in the afternoon
Wind speed: 10-20 mph with gusts to 40 mph 10-20 mph with gusts to 40 mph increasing to 20-35 mph with gusts to 55 mph after midnight 25-40 mph with gusts to 50 mph
Expected snowfall: O in. O in. O in.