THIS AVALANCHE ADVISORY EXPIRED ON January 12, 2018 @ 6:48 am
Avalanche Advisory published on January 11, 2018 @ 6:48 am
Issued by Steve Reynaud - Tahoe National Forest

Moderate avalanche danger continues due to a persistent slab avalanche problem.  Human triggered avalanches remain possible at all elevations.  Evaluate snow and terrain carefully, identify features of concern.

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

Human triggered persistent slab avalanches remain possible on NW-N-NE-E aspects at all elevations.  On Tuesday, we had a natural avalanche occur on this layer in the Carson Pass area.  In other areas, snowpack tests continue to show that this layer is weak, and if triggered, could propagate and cause an avalanche.  Areas near treeline and below treeline seem the most likely places for this weak layer to exist and be reactive.  The facet layer is moist to wet in many areas from the recent rain and warm temperatures and is expected to gain strength as the snowpack refreezes. 

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.

recent observations

*  Consistent unstable snowpack test results yesterday on Tamarack Peak (Mt. Rose area) on a buried layer of facets.  These observations were made on NW-N aspects in near treeline and below treeline terrain.

*  On Tuesday, a natural triggered persistent slab avalanche occurred on Elephants Hump in the Carson Pass area.  Widespread signs of instability with collapsing, cracking, and whumpfing of the snowpack were also observed.

* 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 4+ 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, with large areas of bare ground on the vast majority of southerly aspects at all elevations.

Weather and CURRENT CONDITIONS
weather summary

A weather disturbance moving through the Pacific NW today will bring mid to high level clouds and windy conditions to our forecast area.  Ridge winds are forecasted to gust up to 70 to 90mph this afternoon.  All of the moisture associated with this storm should stay well north of our region.  High pressure builds into our area for the weekend with mild above average temperatures and light winds.  Weather forecast models continue to look favorable for a change next week to a wetter and progressively colder series of storms.

Weather observations from along the Sierra Crest between 8200 ft. and 8800 ft.
0600 temperature: 24 to 37 deg. F.
Max. temperature in the last 24 hours: 37 deg. F.
Average wind direction during the last 24 hours: W to SW
Average wind speed during the last 24 hours: 20 to 30 mph
Maximum wind gust in the last 24 hours: 76 mph
New snowfall in the last 24 hours: Trace to 2 inches
Total snow depth: 22 to 38 inches
Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 7000 ft. to 8000 ft.
Thursday Thursday Night Friday
Weather: Partly cloudy then becoming mostly cloudy. Partly cloudy. Partly cloudy then becoming sunny
Temperatures: 43 to 48 deg. F. 28 to 33 deg. F. 44 to 49 deg. F.
Wind Direction: SW SW SW
Wind Speed: 15 to 25mph. Gusts to 30mph increasing to 55mph in the afternoon. 20 to 30mph with gusts to 60mph decreasing to 10 to 15mph with gusts to 40mph after midnight. 10 to 15mph with gusts to 40mph in the morning then becoming light.
Expected snowfall: 0 in. 0 in. 0 in.
For 8000 ft. to 9000 ft.
Thursday Thursday Night Friday
Weather: Partly cloudy then becoming mostly cloudy. Partly cloudy. Partly cloudy then becoming sunny.
Temperatures: 39 to 44 deg. F. 28 to 33 deg. F. 41 to 47 deg. F.
Wind Direction: W to SW SW W
Wind Speed: W 15 to 25mph with gusts to 50mph increasing to SW 25 to 40mph with gusts to 75mph in the afternoon. W 30 to 45mph with gusts to 90mph becoming SW 20 to 35mph with gusts to 65mph after midnight. 20 to 30mph. Gusts up to 60mph decreasing to 50mph in the afternoon.
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.

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