THIS AVALANCHE ADVISORY EXPIRED ON December 10, 2015 @ 7:00 am
Avalanche Advisory published on December 9, 2015 @ 7:00 am
Issued by Steve Reynaud - Tahoe National Forest

Low avalanche danger remains on all aspects and elevations.  Watch for unstable snow on isolated terrain features.  Early season snowpack conditions exist with the potential to collide with many obstacles.  The avalanche danger will rise as the storm system arrives late tonight and throughout Thursday.

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 ?
  • Aspect/Elevation ?
  • Likelihood ?
    Certain
    Very Likely
    Likely
    Possible
    Unlikely
  • Size ?
    Historic
    Very Large
    Large
    Small

Avalanches will remain unlikely today and normal caution is advised.  Expect a combination of wet surface snow with open, shaded aspects having a breakable/supportable surface crust.  Strong to gale force SW winds will keep the snow surface firm in exposed areas and will impede travel as the day progresses.  Avalanche danger will increase late today/tonight as this strong storm impacts our forecast area.

recent observations

Snow surface conditions yesterday ranged from soft wet surface snow to a variety of supportable and breakable surface crusts. 

Most recent observations throughout the forecast area have pointed to a strengthening snowpack that it is in good shape to handle additional load.  Observations from Tamarack Peak (Mt. Rose area) have shown that the weak basal facets are still present in many locations.  These facets are reactive to snowpack tests showing that propagation is still a possibility on this layer.  In most areas that we have observed, these facets are held in place with terrain features and many anchors (rocks, bushes, logs, etc.)  Uncertainty exists if there is terrain that this weak layer can span which would make the possibility for larger avalanches with additional storm load.  Most likely areas of concern are NW, N, NE aspects, near treeline terrain above 9000'.

Weather and CURRENT CONDITIONS
weather summary

Mild conditions will exist today ahead of a strong storm that is on track to bring high winds and precipitation to the Sierra.  The forecast calls for a chance of light rain tonight with increasing winds into the strong to gale force range.  There is a winter storm warning in effect from 4am Thursday to 4am Friday.  Snow levels should start out around 8000-8500' tonight and lower to 5500' by Thursday mid day.  There is still some uncertainty as to when/how fast snow levels will drop and that will be key with determining snow totals.  Latest guidance from the Reno NWS shows snow accumulations of 1-2' above 7000' with up to 3' possible along the Sierra Crest by Friday morning.

Weather observations from along the Sierra Crest between 8200 ft. and 8800 ft.
0600 temperature: 34 to 36 deg. F.
Max. temperature in the last 24 hours: 41 deg. F.
Average wind direction during the last 24 hours: SW
Average wind speed during the last 24 hours: 25 to 30 mph
Maximum wind gust in the last 24 hours: 60 mph
New snowfall in the last 24 hours: 0 inches
Total snow depth: 15-25 inches
Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 7000 ft. to 8000 ft.
Wednesday Wednesday Night Thursday
Weather: Mostly cloudy. Slight chance of rain in the afternoon. Cloudy. Slight chance of rain in the evening. Then chance of rain and snow after midnight. Cloudy. Showers in the morning then snow in the afternoon.
Temperatures: 43 to 50 deg. F. 29 to 36 deg. F. 30 to 37 deg. F.
Wind Direction: SW SW SW
Wind Speed: 40 to 50mph with gusts to 75mph. 35 to 40mph with gusts to 60mph, increasing to 65 to 70mph with gusts to 105mph after midnight. 60 to 65mph with gusts to 100mph decreasing to 45 to 50mph with gusts to 75mph in the afternoon.
Expected snowfall: 0 in. 0 in. 5 to 12 in.
For 8000 ft. to 9000 ft.
Wednesday Wednesday Night Thursday
Weather: Mostly cloudy then becoming cloudy. Cloudy. Slight chance of rain in the evening. Then chance of rain and snow after midnight. Cloudy. Snow showers in the morning then snow in the afternoon.
Temperatures: 40 to 47 deg. F. 24 to 31 deg. F. 27 to 34 deg. F.
Wind Direction: SW SW SW
Wind Speed: 75 to 80mph decreasing to 65 to 70mph in the afternoon with gusts to 100mph. 55 to 60mph with gusts to 105mph increasing to 75 to 80mph with gusts to 125mph after midnight. 70 to 80mph with gusts to 120mph.
Expected snowfall: 0 in. 2 in. 6 to 14 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.