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 December 28, 2011:


December 28, 2011 at 7:56 am

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


Forecast Discussion:


A weather system passing to the north of the forecast area will bring mid to high level cloud cover and a slight chance of very light precipitation to the region today. Warm air associated with this system has already moved into the forecast area. Remote sensors between 6,200' and 9,650' are reporting above freezing air temperatures this morning. Daytime highs are expected in the mid 30s to upper 40s today for areas above 7,000'. Snow level is forecast around 7,500 to 8,000' with no significant accumulation expected. Ridgetop winds shifted from east to southwest mid day yesterday. Wind speeds remain light this morning, with an increase to moderate to strong west winds expected by this afternoon.

Observations:

Observations made yesterday on Silver Peak (Pole Creek area) and around the Mount Rose area indicate that the rate of changed in the current snowpack picture is slow (more info, photos, pit profiles). Areas along the Sierra Crest from around Donner Summit north to Yuba Pass hold the greatest amount of snow. East wind events during the month of December have scoured significant amounts of snow from wind exposed areas on NW-N-NE-E aspects. Near treeline and below treeline areas that continue to hold snow are generally very faceted and weak with either no overlying slab or a stable, anchored, surface hard slab over faceted snow. The SE-S-SW-W aspects are generally void of snow, except for a few inches here and there in shaded areas.

Avalanche Concerns: Persistent slabs

Avalanche concerns at this time are few. Despite the presence of weak faceted snow on most snow covered slopes, an overlying slab with the necessary characteristics for propagation is absent. In areas where a slab does exist, it is either too weak to sustain propagation or it is sufficiently anchored. If an unstable slab were to be found anywhere in the forecast area, it would exist on a northerly aspect in near treeline terrain with few visible anchors beyond the presence of trees. Continue to exercise caution when traveling in these areas as any instability will exist within surrounding areas of stable snowpack conditions.


The bottom line:

Avalanche danger remains 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 38 deg. F.
Max. temperature in the last 24 hours: 42 to 49 deg. F.
Average wind direction during the last 24 hours: East shifting to southwest.
Average wind speed during the last 24 hours: 15 mph
Maximum wind gust in the last 24 hours: 32 mph
New snowfall in the last 24 hours: O inches
Total snow depth: 4 to 20 inches

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

For 7000-8000 ft:

  Wednesday: Wednesday Night: Thursday:
Weather: Mostly cloudy skies with a slight chance of rain and snow. Mostly cloudy skies with a slight chance of rain and snow. Mostly cloudy skies in the morning, becoming partly cloudy.
Temperatures: 41 to 48 deg. F. 25 to 32 deg. F. 42 to 49 deg. F.
Wind direction: W SW SW
Wind speed: 15 to 25 mph with gusts to 50 mph. 10 to 20 mph with gusts to 55 mph. 10 to 15 mph in the morning increasing to 15 to 25 mph in the afternoon. Gusts to 45 mph.
Expected snowfall: 0 to trace in. 0 to trace in. O in.

For 8000-9000 ft:

  Wednesday: Wednesday Night: Thursday:
Weather: Mostly cloudy skies with a slight chance of snow. Mostly cloudy skies with a slight chance of snow. Mostly cloudy skies in the morning, becoming partly cloudy.
Temperatures: 38 to 45 deg. F. 26 to 33 deg. F. 38 to 45 deg. F.
Wind direction: W W W
Wind speed: 20 to 35 mph with gusts to 55 mph. 20 to 35 mph with gusts to 55 mph. 20 to 30 mph with gusts to 50 mph.
Expected snowfall: 0 to trace in. 0 to trace in. O in.