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 February 1, 2013:


February 1, 2013 at 7:57 am

Avalanche danger is LOW for all elevations and aspects. Normal caution is advised.


Forecast Discussion:


Dominant high pressure remains in place over the forecast area. Sunny skies, light winds, and well above freezing maximum daytime air temperatures are forecast for today. Some cloud cover is expected Saturday and Sunday as a weather system pass to the north of the forecast area. Ridgetop winds shifted to the southwest yesterday and were light to moderate in speed. Light southwest winds are forecast to continued today and tomorrow. Remote sensors are reporting air temperatures in the mid to upper 30s this morning above 8,000'. Air temperatures are forecast to warm into the 40s today for areas above 7,000' .

Recent Observations:

Observations made yesterday near Round Top Peak (Carson Pass area) and on Silver Peak (Pole Creek area) matched well with other observations made around the forecast area over the past few days. Daytime warming created wet surface snow on southerly aspects during the mid day and afternoon hours. On Silver Peak, 1 inch of wet snow existed on top of supportable rain crust on SE aspects in the 7,000' to 8,000' range at 11:45 am (pit profile, more info). In the Round Top area, 2 to 3 inches of wet snow existed on top of supportable crust on S aspects in the 8,500' to 9,500' range at 1pm.

On the N side of the Round Top Peak/Sisters Peaks area, a wind slab was noted on a W aspect slope micro feature where cross loading had occurred last Monday under strong NE winds. Similar to other wind slabs observed over the past several days, this wind slab was shallow with a maximum depth of 8 inches. Snowpit data indicated that failure of this wind slab on near crust facets below the slab remained theoretically possible, but difficult to accomplish on a slope scale (photos, video, more info).

Avalanche Concerns:

Shallow wind slabs that formed last Monday near and along ridgelines in near and above treeline areas have shown good stability over the past three days. Human triggering of a shallow wind slab is unlikely today, but could theoretically occur. Above 8,600' in near or above treeline terrain on a SE-S-SW-W aspect, especially in an area of complex or extreme terrain is the most likely location. Maximum slab depth is unlikely to exceed 6 to 8 inches. While snowpit data has indicated possible slab failure on either lower density storm snow or near crust facets below these slabs, no reports of intentional or unintentional human triggered wind slab avalanches have been received since these slabs formed. Failure of these slabs has proven much more difficult to trigger on a slope scale than in the small scale of the snowpit.

Wet surface snow will develop on SE-S-SW aspects in response to daytime warming. During the afternoon hours, small mostly inconsequential human triggered loose wet snow avalanches and roller balls may occur on SE-S-SW aspects on slopes 37 degrees and steeper. The small size of any loose wet snow avalanches is unlikely to pose a significant threat to backcountry travelers. Keep in mind that undesirable interaction with secondary terrain features such as cliffs, terrain traps, and trees can increase consequences significantly.


The bottom line:

Avalanche danger is LOW for all elevations and aspects. Normal caution is advised.


Brandon Schwartz - Avalanche Forecaster, Tahoe National Forest


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

0600 temperature: 33 to 39 deg. F.
Max. temperature in the last 24 hours: 42 to 49 deg. F.
Average wind direction during the last 24 hours: Southwest
Average wind speed during the last 24 hours: 20 mph
Maximum wind gust in the last 24 hours: 30 mph
New snowfall in the last 24 hours: O inches
Total snow depth: 56 to 81 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, becoming partly cloudy.
Temperatures: 41 to 48 deg. F. 20 to 28 deg. F. 38 to 45 deg. F.
Wind direction: SW SW SW
Wind speed: Light winds Light winds Light winds
Expected snowfall: O in. O in. O in.

For 8000-9000 ft:

  Friday: Friday Night: Saturday:
Weather: Sunny skies. Clear skies. Sunny skies, becoming partly cloudy.
Temperatures: 39 to 46 deg. F. 21 to 28 deg. F. 38 to 44 deg. F.
Wind direction: SW SW SW
Wind speed: 10 to 15 mph in the morning, becoming light. Light winds Light winds
Expected snowfall: O in. O in. O in.