THIS AVALANCHE ADVISORY EXPIRED ON December 8, 2014 @ 6:56 am
Avalanche Advisory published on December 7, 2014 @ 6:56 am
Issued by Brandon Schwartz - Tahoe National Forest

Avalanche danger is LOW for all elevations and aspects. Low likelihood high consequence large size persistent slab avalanches remain a lingering concern in isolated areas above 9,000' on NW-N-NE aspects both above and below treeline.

1. Low

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

1. Low

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

1. Low

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Below Treeline
Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.
    Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.
Avalanche Problem 1: Persistent Slab
  • Type ?
  • Aspect/Elevation ?
  • Likelihood ?
    Certain
    Very Likely
    Likely
    Possible
    Unlikely
  • Size ?
    Historic
    Very Large
    Large
    Small

Persistent slabs remain a lingering concern in isolated areas above 9,000' on NW-N-NE aspects both above and below treeline. Recent snowpit data has shown that the Dec 2 facet layer is gaining strength in most, but not all areas. At this time, triggering a persistent slab avalanche is a low likelihood, high consequence event. Given the location of the problematic weak layer near the base of the snowpack, nearly all of the existing snowpack (2 to 4+ ft deep) will be involved. The potential avalanche size and the density of the overlying slab make survival without significant traumatic injury an unrealistic expectation. The most likely trigger points exist at relative shallow areas of the snowpack. These are commonly found near exposed rocks, isolated trees, and along cliff bands, making travel in northerly aspect complex terrain above 9,000' a poor choice at this time.

recent observations

Observations made yesterday on Andesite Ridge (Donner Summit area) and on Powderhouse Peak (Luther Pass area) revealed stable snowpack conditions. Evidence of rain on snow existed up to 8,300' on Powderhouse Peak and potentially higher in the Donner Summit area. Snowpit tests targeting the Dec 2 facet layer on Powderhouse Peak at 9,260' revealed increasing strength of this layer. Other recent observations targeting this same layer have shown mixed results on Tamarack Peak (Mount Rose area) and unstable results on Red Lake Peak (Carson Pass area).

Weather and CURRENT CONDITIONS
weather summary

Increasing cloud cover and ridgetop winds are forecast today as a weather disturbance moves through the region. A slight chance of snow showers exists for tonight with snow level around 7,000'. No accumulation is expected. Remote sensors are reporting air temperatures this morning in the mid 30s at 8,000'. Maximum daytime air temperatures are expected to reach to upper 30s to upper 40s today for areas above 7,000' as the current run of above average air temperatures continues. Light to moderate speed ridgetop winds this morning are forecast to increase to moderate to strong in speed this afternoon with gusts to 50 mph.

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: 36 to 39 deg. F.
Average wind direction during the last 24 hours: Southwest
Average wind speed during the last 24 hours: 25 mph
Maximum wind gust in the last 24 hours: 49 mph
New snowfall in the last 24 hours: 0 to trace inches
Total snow depth: 13 to 30 inches
Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 7000 ft. to 8000 ft.
Sunday Sunday Night Monday
Weather: Partly cloudy skies, becoming mostly cloudy. Mostly cloudy skies with a slight chance of showers after midnight. Mostly cloudy skies with a slight chance of showers in the morning.
Temperatures: 42 to 48 deg. F. 22 to 29 deg. F. 37 to 44 deg. F.
Wind Direction: SW SW SW
Wind Speed: 15 to 20 mph. Gusts to 30 mph in the afternoon. 15 to 25 mph with gusts to 40 mph. 25 to 30 mph with gusts to 40 mph in the morning, decreasing to 15 to 20 mph with gusts to 30 mph in the afternoon.
Expected snowfall: 0 in. 0 to trace in. 0 to trace in.
For 8000 ft. to 9000 ft.
Sunday Sunday Night Monday
Weather: Partly cloudy skies, becoming mostly cloudy. Mostly cloudy skies with a slight chance of showers after midnight. Mostly cloudy skies with a slight chance of showers in the morning.
Temperatures: 38 to 44 deg. F. 21 to 28 deg. F. 34 to 41 deg. F.
Wind Direction: SW SW SW
Wind Speed: 20 to 25 mph with gusts to 35 mph, increasing to 30 to 35 mph with gusts to 50 mph in the afternoon. 30 to 40 mph. Gusts to 60 mph decreasing to 50 mph after midnight. 25 to 35 mph. Gusts to 55 mph decreasing to 40 mph in the afternoon.
Expected snowfall: 0 in. 0 to trace in. 0 to trace 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.