THIS AVALANCHE ADVISORY EXPIRED ON January 7, 2014 @ 6:59 am
Avalanche Advisory published on January 6, 2014 @ 6:59 am
Issued by Andy Anderson - Tahoe National Forest

Pockets of MODERATE avalanche danger may still exist on near and below treeline NW-N-NE aspects steeper than 32 degrees where consistent snow cover exists. Persistent slabs continue to lurk in these areas. Human triggered avalanches remain possible in these places. Lack of snow in all other areas has made the avalanche danger LOW or non-existent.

1. Low

?

Above Treeline
Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.

2. Moderate

?

Near Treeline
Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.

2. Moderate

?

Below Treeline
Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.
    Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.
Avalanche Problem 1: Persistent Slab
  • Type ?
  • Aspect/Elevation ?
  • Likelihood ?
    Certain
    Very Likely
    Likely
    Possible
    Unlikely
  • Size ?
    Historic
    Very Large
    Large
    Small

Human triggered persistent slab avalanches remain possible on some NW-N-NE aspects in near and below treeline terrain. These slopes also represent the best places for snow travel because they have the most consistent snow cover. Areas where a shallower snowpack connected to deeper snow exists or trigger points like shallowly buried rocks represent the most likely places to trigger an avalanche on these slopes. Field observations since Dec. 7th have shown variability concerning where the snowpack may remain unstable and where more stable conditions exist. In general observations from the Yuba Pass, Mount Rose, Donner Summit, West Shore Tahoe, and Echo Summit areas have shown significantly less ongoing instability and in some cases stable conditions near and below treeline on NW-N-NE aspects.

The increase in variability and uncertainty associated with the persistent slabs makes accessing snowpack stability difficult. Even though most observations may point to a stable slope, finding one hidden trigger point could start a failure and cause an avalanche. Traveling on slopes less steep than 30 degrees that remain disconnected from steeper and deeper terrain represents a fun and safe plan when persistent slabs like this exist.

These kind of avalanches should remain small due to the lack of snow; however, getting caught in one of them will result in collisions with rocks, logs, or trees due to that same shallow snowpack.

recent observations

Variable snow conditions and inconsistent data concerning stability existed in the Deep Creek drainage (more info, snowpit) yesterday. Snow surfaces ranged from breakable crusts to soft unconsolidated snow to hard icy surfaces to dirt. In areas where consistent snow cover did exist (mostly northerly aspects near the creast above 7800 ft.) the Dec. 7th facet layer remains buried in the bottom third of the snowpack. Some tests on this layer indicated that fractures can still travel along the persistent weak layer, and other tests pointed to a more stable snowpack. For the first time since Dec. 7th, no human triggered collapsing or cracking occurred in the Deep Creek area.

Observations have shown similar inconsistent results and variable conditions across the forecast area. In some areas the Dec. 7th facet layer remains active and in other areas no signs of instability exist. Overall observations show a snowpack whose stability or instability varies greatly from slope to slope or even across an individual slope. Stability or instability has become difficult to access.

Recently, the Carson Pass and Pole Creek areas have shown continued obvious signs of instability. The West Shore and and Deep Creek areas have shown a mix stable and unstable results. The Yuba Pass, Donner Summit, and Mount Rose areas have shown better overall snowpack stability with few or no signs of instability. Of course these more stable areas areas also have the most shallow snowpack with more exposed rocks, ground, trees, bushes, logs, stumps, and other obstacles.

Weather and CURRENT CONDITIONS
weather summary

Some cloud cover and increased SW winds should start to develop over the region today and tonight ahead of a weak low pressure. This system should pass to the north tomorrow with the clouds and wind representing the main impacts to the forecast area. This system should also temporarily weaken the high pressure rdige that has been dominating the region allowing another weak, dry low pressure to affect the area on Wednesday.

Weather observations from along the Sierra Crest between 8200 ft. and 8800 ft.
0600 temperature: 30 to 40 deg. F.
Max. temperature in the last 24 hours: 36 to 46 deg. F.
Average wind direction during the last 24 hours: E shifting to the SW after midnight
Average wind speed during the last 24 hours: 10 to 20 mph
Maximum wind gust in the last 24 hours: 40 mph
New snowfall in the last 24 hours: 0 inches
Total snow depth: 7 to 13 inches
Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 7000 ft. to 8000 ft.
Monday Monday Night Tuesday
Weather: Partly cloudy becoming mostly cloudy during the day Mostly cloudy Mostly cloudy
Temperatures: 42 to 50 deg. F. 22 to 32 deg. F. 36 to 46 deg. F.
Wind Direction: Variable Southwest Southwest
Wind Speed: Light 10 to 15 mph with gusts to 25 mph 15 to 20 mph with gusts to 30 mph
Expected snowfall: 0 in. 0 in. 0 in.
For 8000 ft. to 9000 ft.
Monday Monday Night Tuesday
Weather: Partly cloudy becoming mostly cloudy during the day Mostly cloudy Mostly cloudy
Temperatures: 35 to 45 deg. F. 20 to 30 deg. F. 30 to 40 deg. F.
Wind Direction: Southwest Southwest Southwest
Wind Speed: 5 to 15 mph with gusts to 25 mph in the afternoon 20 to 30 mph with gusts to 50 mph 15 to 25 mph with gusts to 45 mph
Expected snowfall: 0 in. 0 in. 0 in.
Disclaimer

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.