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 13, 2012:


January 13, 2012 at 7:56 am

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


Forecast Discussion:


The high pressure ridge over the forecast area will continue to dominate the weather at least through Saturday. Winds should remain light and variable today before shifting more to the southwest tomorrow. Some warmer air should also move into the region with these southwest winds making tomorrow's highs slightly warmer than today's. For today the forecast calls for daytime highs in the the upper 30's and low 40's above 7000 ft.  A slight inversion exists again this morning due to cold air pooling in the valley's below 7000 ft. These inversions have been slower to lift due to the lack of wind.

Observations:

Observations across the region have shown that the paltry snowpack remains highly variable from place to place. Snow coverage only exists on the NW-N-NE-E aspects. Even on these aspects snow coverage is patchy especially south of Barker Pass along the Sierra Crest and in areas on the east side of the Lake. North of Barker Pass along the Sierra Crest more snow exists. In these areas where a deeper snowpack exists,  more rain and warming occurred capping the snowpack with a rain crust and creating melt freeze conditions within the snowpack. As the snowpack refroze, it grew much stronger and more stable in most of these areas. Some recent observations have shown weak sugary facets reforming near the rain crusts. In more shallow higher elevation areas south of Barker Pass and east of Lake Tahoe where less warming occurred and less snow exists, more layers of weak facets exist; however, more anchors also protrude through the snowpack disrupting any weak layers and holding the snowpack in place in most areas. The strong N-NE-E winds earlier this season scoured most of the snow away from the exposed N-NE-E aspects leaving behind mix of hard wind scoured surfaces, bare ground, and hard icy snow left over from last year.

Avalanche Concerns:

Avalanche activity remains unlikely for now. The areas where a slab exists on top of weak snow are small and very isolated. Even where these conditions exist, actually triggering a fracture in the snowpack would prove difficult. Weak layers have shown signs of reforming in some areas. Depending on how widespread and developed these weak layers become, they could create problems when new snow arrives. The avalanche danger remains low, but plenty of other hazards exist in the backcountry including very icy slopes with lots of rocks and trees at the bottom and in the middle of these slopes. Continue to use caution when traveling in the backcountry.


The bottom line:

LOW avalanche danger exists for all elevations and aspects. Use normal caution while traveling 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: 34-38 deg. F.
Max. temperature in the last 24 hours: 37-43 deg. F.
Average wind direction during the last 24 hours: East shifting to the southwest
Average wind speed during the last 24 hours: 15-20 mph
Maximum wind gust in the last 24 hours: 36 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 Clear Partly cloudy
Temperatures: 37-44 deg. F. 24-30 deg. F. 38-45 deg. F.
Wind direction: Variable Variable Southwest
Wind speed: Light Light 10-15 mph
Expected snowfall: O in. O in. O in.

For 8000-9000 ft:

  Friday: Friday Night: Saturday:
Weather: Sunny Clear Partly cloudy
Temperatures: 35-42 deg. F. 22-29 deg. F. 35-42 deg. F.
Wind direction: Variable Variable Southwest
Wind speed: Light Light 15-25 mph with gusts to 35 mph
Expected snowfall: O in. O in. O in.