THIS AVALANCHE ADVISORY EXPIRED ON February 5, 2016 @ 7:00 am
Avalanche Advisory published on February 4, 2016 @ 7:00 am
Issued by Andy Anderson - Tahoe National Forest

MODERATE avalanche danger may form on sun-exposed near and below treeline E-SE-S-SW-W aspects as well as on some above treeline SE-S-SW aspects due to the possibility of loose wet snow instabilities. Wet surface snow and small instabilities like pin wheels and roller balls can indicate that loose wet avalanches have become possible. The amount of warming that actually occurs today will dictate how widespread these possible wet snow instabilities may be. 

2. Moderate

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

2. Moderate

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

2. Moderate

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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: Loose Wet
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    Certain
    Very Likely
    Likely
    Possible
    Unlikely
  • Size ?
    Historic
    Very Large
    Large
    Small

A mostly clear cold night should have allowed the wet snow that formed yesterday to refreeze during the night. Sunshine and warm temperatures today may allow some some loose wet snow instabilities to become possible this afternoon as the snow warms back up on steep sun exposed SE-S-SW aspects and some lower elevation E and W aspects. Small pinwheels, roller balls, and point release avalanches (sluffs) should represent the majority of the loose wet instabilities, but a few could entrain enough snow to cause issues for backcountry travelers since they could involve most of the snow above the uppermost rain crust. The north winds and clear skies should limit these wet snow issues to the most sun exposed aspects. If the stronger north winds or lower day time highs than forecasted occur, these wet snow instabilities will be more isolated and smaller. If weaker north winds and higher temperatures than forecasted occur, these wet snow instabilities could become more widespread and larger. 

recent observations

Yesterday observations on Andesite Ridge in the morning and on Angora Peak in the afternoon showed 10 to 15 inches of unconsolidated soft snow sitting on top of a thick rain crust on the sheltered northerly aspects. On more exposed near and above treeline slopes on all aspects, a mix of firm icy crusts and wind scoured surfaces existed on Andesite Peak. Snowpit tests, ski cuts on test slopes, and general observations did not reveal any signs of instability in these areas where the snow surface remained cold. In the afternoon on the lower elevations of Angora Peak, ski cuts on steep slopes triggered loose wet snow instabilities like point releases and pinwheels. Across the Lake where less cloud cover existed yesterday, more widespread wet snow instability existed. Large loose wet snow avalanches resulted from ski cuts on southerly facing slopes on Slide Mountain in the Mt. Rose backcountry. Reports indicated that these loose wet avalanches entrained all of the most recent snow and slid on the rain crust 12 to 16 inches below the surface.  

Weather and CURRENT CONDITIONS
weather summary

A trace to 1 inch of new snow fell on some areas of the region yesterday due to a small low pressure system passing through the area. This system has moved eastward and a high pressure ridge has started to build over the region. Winds started to shift to the north and northeast this morning and these northerly winds should become widespread by this afternoon. They should remain moderate to light in speed and decrease and shift back to the southwest over the next 24 to 36 hours. The high pressure ridge should also bring clearing skies and warmer temperatures to the forecast area today and another cold clear night tonight. By tomorrow some cloud cover could start to rebuild over the region as a small low pressure system approaches the CA-OR border. 

Weather observations from along the Sierra Crest between 8200 ft. and 8800 ft.
0600 temperature: 20 to 24 deg. F.
Max. temperature in the last 24 hours: 33 to 39 deg. F.
Average wind direction during the last 24 hours: Southwest shifting to north early this morning
Average wind speed during the last 24 hours: 15 to 25 mph
Maximum wind gust in the last 24 hours: 54 mph
New snowfall in the last 24 hours: trace to 1 inches
Total snow depth: 71 to 93 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 in the morning becoming mostly sunny by mid day Partly cloudy to mostly clear Partly cloudy becoming mostly cloudy
Temperatures: 30 to 38 deg. F. 12 to 20 deg. F. 32 to 39 deg. F.
Wind Direction: Southwest shifting to the north in the afternoon East Variable becoming south in the afternoon
Wind Speed: 15 to 20 mph with gusts to 25 mph 10 to 15 mph becoming light in the evening Light increasing to 10 to 15 mph in the afternoon
Expected snowfall: 0 in. 0 in. 0 in.
For 8000 ft. to 9000 ft.
Thursday Thursday Night Friday
Weather: Mostly cloudy in the morning becoming mostly sunny by mid day Partly cloudy to mostly clear Partly cloudy becoming mostly cloudy
Temperatures: 28 to 37 deg. F. 10 to 17 deg. F. 30 to 37 deg. F.
Wind Direction: West shifting to the north in the afternoon East Southeast shifting to the southwest in the afternoon
Wind Speed: 20 to 25 mph with gusts to 40 mph 10 to 20 mph with gusts to 30 mph in the evening 10 to 15 mph with gusts to 30 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.