THIS AVALANCHE FORECAST EXPIRED ON December 7, 2016 @ 6:40 am
Avalanche Forecast published on December 6, 2016 @ 6:40 am
Issued by Brandon Schwartz - Tahoe National Forest

LOW avalanche danger continues for all elevations and aspects. Isolated areas of instability are not impossible. Normal caution is advised. Early season conditions exist with numerous shallow buried and exposed obstacles in most areas.

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: Normal Caution
  • Type ?

Strong to gale force winds out of both the SW and NE over the past 7 to 10 days has created widespread areas of eroded snow surfaces and pockets of dense wind slab. Observations have indicated that these pockets of wind slab are generally stable, but isolated areas of instability are not impossible somewhere within the forecast area. Employing normal caution in the form of identifying and discussing potential areas of hazard with travel partners, one at a time travel in or below avalanche terrain, and moving from one well established island of safety to another will serve to keep the widest possible margin of safety.

North aspects continue to hold faceted old snow near the base of the snowpack, usually on top of a ground level ice layer. This weak layer is found on N aspects along the Sierra Crest above about 8,300' and in the Mount Rose area above about 9,300'. Currently, triggering failure of this weak layer is very difficult and avalanche activity associated with it is unlikely. Day to day snowpit data continues to indicate that this weak layer could become problematic under future loading conditions. Normal caution is reasonable for managing this issue today, but it is well advised not to accept marginal islands of safety (ie using one or more large trees still within the runout zone as a stopping point) when dealing with this type of weak layer that is deeper in the snowpack.

recent observations
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Observations made yesterday in the upper portions of the Deep Creek Drainage (Pole Creek/Deep Creek area) revealed ongoing issues on N aspects above 8,300' where the faceted old snow layer existed in the lower portion of the snowpack. Snowpit tests repeatedly indicate that the weak layer and overlying slab hold properties that will allow for propagation following weak layer failure. Snowpit tests also repeatedly indicate that at the current time, triggering weak layer failure is very unlikely until significant new loading from snow/rain occurs.

Additional observations received from Mt. Judah (Donner Summit area) and Tamarack Peak (Mount Rose area) matched well with other recent observations from around the forecast area. The Mt. Judah observations further indicate that problematic faceted snow along the Sierra Crest is limited to N aspects above 8,300'. Both observations indicate that significant winds effects have occurred throughout the forecast area.

Weather and CURRENT CONDITIONS
weather summary

A weather system passing to the NE of the forecast area will bring some increased cloud cover and a slight chance of light snow showers this afternoon. Ridgetop winds are expected to return to strong to gale force today with gusts to 95 mph possible. Cold air will move in tonight behind the passing weather system. Single digit to low teen air temperatures are forecast as overnight lows for all elevations. A brief period of light to moderate speed NE wind is expected tonight before winds shift back to the W ahead of the next storm system, forecast to impact the area late Wednesday.

CONDITIONS ALONG THE SIERRA CREST BETWEEN 8200 FT. AND 9200 FT. IN THE LAST 24 HOURS
Weather Station Map
Weather Station Table
6am temperature: 14 to 25 deg. F.
Max. temperature: 31 to 38 deg. F.
Average ridgetop wind direction: SW
Average ridgetop wind speed: 27 mph
Maximum ridgetop wind gust: 50 mph
New snowfall: 0 inches
Total snow depth: 10 to 21 inches
Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 7000 ft. to 8000 ft.
Tuesday Tuesday Night Wednesday
Weather: Partly cloudy skies with a slight chance of snow showers in the afternoon. Partly cloudy skies, becoming clear. Sunny skies becoming mostly cloudy. A slight chance of snow showers in the afternoon.
Temperatures: 26 to 32 deg. F. 7 to 12 deg. F. 26 to 31 deg. F.
Mid Slope Winds: W NW W
Wind Speed: 15 to 25 mph with gusts to 55 mph. 10 to 15 mph with gusts to 35 mph in the evening, becoming light. 10 to 20 mph.
Expected snowfall: 0 to trace 0 0 to trace
For 8000 ft. to 9000 ft.
Tuesday Tuesday Night Wednesday
Weather: Partly cloudy skies with a slight chance of snow showers in the afternoon. Partly cloudy skies, becoming clear. Sunny skies becoming mostly cloudy. A slight chance of snow showers in the afternoon.
Temperatures: 23 to 31 deg. F. 6 to 11 deg. F. 24 to 29 deg. F.
Ridge Top Winds: W NW shifting to NE W
Wind Speed: 30 to 45 mph. Gusts to 95 mph decreasing to 85 mph in the afternoon. 15 to 25 mph with gusts to 65 mph, shifting and decreasing to 15 to 20 mph with gusts to 40 mph after midnight. 15 to 20 mph with gusts to 45 mph.
Expected snowfall: 0 to trace 0 0 to trace
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.

For a recorded version of the Avalanche Advisory call (530) 587-3558 x258