THIS AVALANCHE ADVISORY EXPIRED ON January 11, 2018 @ 6:55 am
Avalanche Advisory published on January 10, 2018 @ 6:55 am
Issued by Steve Reynaud - Tahoe National Forest

Moderate avalanche danger exists throughout the forecast area due to persistent slab and wind slab avalanche problems.  Human triggered avalanches are possible today.  Persistent slab avalanches will be possible at all elevations and wind slab avalanches will be possible in near and above treeline terrain.  Heightened avalanche conditions exist on specific terrain features.

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: Persistent Slab
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Persistent slab avalanches will continue to be possible on NW-N-NE-E aspects at all elevations.  A natural persistent slab avalanche occurred yesterday at 8400' on a North aspect in the Carson Pass area.  Widespread signs of instability also existed in the area with cracking, collapsing, and whumpfing of the snowpack.  Terrain near treeline and below treeline seem the most likely areas for the combination of weak faceted layer and overlying slab to exist.  These persistent slabs could exhibit wet slab characteristics in areas below 8500' to 9000' due to recent rain and warm temperatures.  In most areas, the facet layer is moist to wet and is expected to gain strength once the snowpack refreezes.  But at this point, the weak layer has a large load of heavy wet snow on top and is continuing to be reactive.

Look for collapsing, cracking, or whumpfing of the snowpack.  Start zones could be low or mid slope in near treeline or below treeline terrain.  Practice safe travel protocols and avoid avalanche run out zones.  These avalanches are capable of injuring or burying a backcountry user.

Avalanche Problem 2: Wind Slab
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Small wind slab development was observed yesterday.  West winds will increase today and will have the potential to form new wind slabs in near and above treeline terrain.  These wind slabs are expected to be small at elevations below 8500'.  Where more snow is available for wind transport, wind slabs could be larger and add to existing wind slabs that formed yesterday in areas above 9000'.

Look for blowing snow, cornice formation, wind pillows, in areas along ridgelines and wind exposed terrain.  Avoid steep wind loaded terrain.

recent observations

*  Natural triggered persistent slab avalanche on Elephants Hump in the Carson Pass area.  Widespread signs of instability with collapsing, cracking, and whumpfing of the snowpack.

Facet layer is moist to wet in most areas below 9000'. 

*  2 to 3'' of new snow in the Tamarack Peak (Mt. Rose area).  Wet snow conditions existed below 9300'.  Small wind slabs were triggered off of ridgeline.

* NW-N-NE aspects above 8,000' in the Mt. Rose area and along the Sierra Crest north of Emerald Bay hold the best snow coverage at 2 to 3+ feet. Overall less snow cover exists south of Emerald Bay. Areas of decent coverage exist above 8,500' on NW-N-NE aspects in the Carson Pass area.  Coverage decreases on all other aspects. Large areas of bare ground exist on the vast majority of southerly aspects at all elevations.

Weather and CURRENT CONDITIONS
weather summary

Isolated light snow showers are possible today with breezy conditions.  Similar conditions will exist on Thursday as storms move past our area to the North.  A ridge will build over our region late this week and through the weekend bringing dry and mild conditions.  Weather forecast models are increasing hope that our area will return to a wet pattern by the end of next week.

Weather observations from along the Sierra Crest between 8200 ft. and 8800 ft.
0600 temperature: 26 to 31 deg. F.
Max. temperature in the last 24 hours: 40 deg. F.
Average wind direction during the last 24 hours: SW switching to W
Average wind speed during the last 24 hours: 30 to 50 mph
Maximum wind gust in the last 24 hours: 66 mph
New snowfall in the last 24 hours: 0 to 1 inches
Total snow depth: 20 to 38 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. Scattered showers. Partly cloudy. Partly cloudy then becoming mostly cloudy.
Temperatures: 40 to 45 deg. F. 27 to 32 deg. F. 45 to 51 deg. F.
Wind Direction: W SW
Wind Speed: 15 to 20mph with gusts to 35mph. Light winds 10 to 15mph with gusts to 35mph in the afternoon.
Expected snowfall: Up to 1 in. 0 in. 0 in.
For 8000 ft. to 9000 ft.
Wednesday Wednesday Night Thursday
Weather: Mostly cloudy. Scattered snow showers. Partly cloudy. Partly cloudy then becoming mostly cloudy.
Temperatures: 37 to 42 deg. F. 27 to 32 deg. F. 43 to 49 deg. F.
Wind Direction: W W W
Wind Speed: 20 to 35mph. Gusts to 60mph increasing to 70mph in the afternoon. 20 to 30mph. Gusts to 60mph decreasing to 45mph after midnight. 20 to 30mph. Gusts to 50mph increasing to 60mph in the afternoon.
Expected snowfall: Up to 1 to 2 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.

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