THIS AVALANCHE ADVISORY EXPIRED ON January 10, 2014 @ 6:51 am
Avalanche Advisory published on January 9, 2014 @ 6:51 am
Issued by Brandon Schwartz - Tahoe National Forest

Avalanche danger is LOW for snow covered areas at all elevations on NW-N-NE-E aspects. For all other areas, avalanche danger is generally nonexistent due to a lack of snow cover.

1. Low

?

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

?

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: Normal Caution
  • Type ?
  • Aspect/Elevation ?
  • Likelihood ?
    Certain
    Very Likely
    Likely
    Possible
    Unlikely
  • Size ?
    Historic
    Very Large
    Large
    Small

Generally stable avalanche conditions exist around the forecast area on a regional scale. The remote possibility of finding that third scenario of the unlikely but not impossible to trigger persistent slab is just enough to warrant continued caution and diligent best practice travel techniques in the backcountry. The faceted Dec 7 persistent weak layer remained reactive for 3+ weeks following the snowfall event that buried and loaded it. It has recently gone quiet in the areas sampled by field observations. Near treeline and below treeline slopes on NW-N-NE aspects that hold continuous snow cover deserve slope by slope evaluation for an isolated persistent slab avalanche problem. Look for stronger, higher density snow on top of lower density snow. If that is the case, stop and evaluate if the weak layer below the slab remains reactive.

recent observations

Observations made yesterday on Andesite Peak (Donner Summit area) fell in line with other observations from around the forecast area over the past week. Where areas of continuous snow cover exist near treeline and below treeline on NW-N-NE aspects, generally one of two snowpack scenarios is found. Scenario 1: The faceted Dec 7 layer has gained enough strength that failure has become unlikely under the current level of load. Scenario 2: The slab sitting on top of the Dec 7 facet layer has lost so much cohesion through the near surface faceting process that it will no longer sustain propagation upon collapse. The slab has literally disintegrated. Either way human triggered avalanches have become unlikely. Finding a third scenario of a lingering pocket of isolated persistent slab instability on an isolated terrain feature somewhere within the forecast area is unlikely but not impossible as persistent weak layers and spatial variability are known to present that way.

Weather and CURRENT CONDITIONS
weather summary

The weather system passing to the north of the forecast area has brought cloud cover and increased west winds as advertised. The winds have mixed out the inversion layer with 20s at the mid and upper elevations and 30s this morning on the mountain valley floors. Some very light snow showers remain possible today, with no accumulation expected. Thick high level cloud cover and moderate to strong west winds are forecast to continue over the area today and tomorrow ahead of the next weather system expected to reach the forecast area on Saturday.

Weather observations from along the Sierra Crest between 8200 ft. and 8800 ft.
0600 temperature: 24 to 30 deg. F.
Max. temperature in the last 24 hours: 32 to 41 deg. F.
Average wind direction during the last 24 hours: West
Average wind speed during the last 24 hours: 30 mph
Maximum wind gust in the last 24 hours: 51 mph
New snowfall in the last 24 hours: 0 to trace 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.
Thursday Thursday Night Friday
Weather: Mostly cloudy skies. Mostly cloudy skies. Mostly cloudy skies.
Temperatures: 30 to 37 deg. F. 19 to 26 deg. F. 42 to 49 deg. F.
Wind Direction: West West Southwest
Wind Speed: 20 to 30 mph with gusts to 45 mph. 20 to 30 mph with gusts to 45 mph. 20 to 30 mph with gusts to 40 mph.
Expected snowfall: 0 to trace in. 0 in. 0 in.
For 8000 ft. to 9000 ft.
Thursday Thursday Night Friday
Weather: Mostly cloudy skies. Mostly cloudy skies. Mostly cloudy skies.
Temperatures: 26 to 33 deg. F. 18 to 25 deg. F. 39 to 46 deg. F.
Wind Direction: West Northwest Northwest
Wind Speed: 30 to 35 mph with gusts to 55 mph, increasing to 40 to 45 mph with gusts to 65 mph in the afternoon. 35 to 45 mph with gusts to 65 mph. 35 to 45 mph with gusts to 65 mph.
Expected snowfall: 0 to trace 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.