THIS AVALANCHE ADVISORY EXPIRED ON March 6, 2017 @ 6:40 am
Avalanche Advisory published on March 5, 2017 @ 6:40 am
Issued by Steve Reynaud - Tahoe National Forest

Considerable avalanche danger exists at all elevations due to wind slab, storm slab, and loose dry avalanche problems.  Dangerous avalanche conditions exist with natural triggered and human triggered avalanches likely today.  Cautious route finding and conservative decision making are essential.

3. Considerable

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Above Treeline
Dangerous avalanche conditions. Careful snowpack evaluation, cautious route-finding and conservative decision-making essential.

3. Considerable

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Near Treeline
Dangerous avalanche conditions. Careful snowpack evaluation, cautious route-finding and conservative decision-making essential.

3. Considerable

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Below Treeline
Dangerous avalanche conditions. Careful snowpack evaluation, cautious route-finding and conservative decision-making essential.
    Dangerous avalanche conditions. Careful snowpack evaluation, cautious route-finding and conservative decision-making essential.
Avalanche Problem 1: Wind Slab
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Wind slabs will be likely on NW-N-NE-E-SE-S aspects in near treeline and above treeline areas.  Additional snow today with strong to gale force SW/W winds will continue wind slab development.  These wind slabs could be natural or human triggered and well over 2 feet deep in size with severe consequences.

Look for blowing snow, cornice formation, and wind pillows.  Avoid steep wind loaded terrain and run out zones below wind loaded terrain.

Avalanche Problem 2: Storm Slab
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Storm slabs will be likely on all aspects in near treeline and below treeline protected terrain.  These storm slabs could be up to 2 feet deep and may have trouble bonding to the old snow surface or within the storm snow.  Cold temperatures may further prolong the bonding process.  Periods of increased snowfall rates this morning may also add to instability.  Look for cracking around skis and any signs of cohesion within the storm snow.  Avoid slopes that show signs of unstable snow.   

Avalanche Problem 3: Loose Dry
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Loose dry avalanches are likely on all aspects in wind protected areas on slopes steeper than 35 degrees.  Most of these will occur in below treeline terrain but it's possible in other wind protected areas where unconsolidated storm snow exists.  These loose dry avalanches are expected to be small but could be large enough to carry a backcountry user into rocks or trees where injury could occur.  Terrain traps could also increase the consequences of a loose dry avalanche.

recent observations

Observations were made and received yesterday from Tamarack Peak (Mt. Rose area), Negro Canyon (Donner Summit area), and Wheeler Ridge (Bear Valley area).  A wind slab avalanche was reported from Wheeler Ridge that was skier triggered and may have involved a cornice failure.  Strong SW winds were reported at all areas with varying amounts of snow available for transport.  Graupel was reported as the storm began on Donner Summit around 3:30pm. 

Weather and CURRENT CONDITIONS
weather summary

A winter storm with moderate to heavy snow will continue through today.  8 to 12'' of snow fell overnight along the Sierra Crest with snow levels below 5000'.  On and off snow showers will continue through today before slowing down later this afternoon and evening.  Up to an additional 6 to 12'' of snow is possible for today with below average temperatures and strong to gale force SW/W winds along ridges and peaks.  More snow is possible tonight and into Monday with limited amounts expected.  High pressure will return later in the week with the possibility of yet another wet pattern for next weekend.

Weather observations from along the Sierra Crest between 8200 ft. and 8800 ft.
0600 temperature: 14 to 16 deg. F.
Max. temperature in the last 24 hours: 36 deg. F.
Average wind direction during the last 24 hours: SW
Average wind speed during the last 24 hours: 40 to 50 mph
Maximum wind gust in the last 24 hours: 116 mph
New snowfall in the last 24 hours: 8 to 12 inches
Total snow depth: 137 to 186 inches
Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 7000 ft. to 8000 ft.
Sunday Sunday Night Monday
Weather: Cloudy. Snow showers. Cloudy. Snow showers. Mostly cloudy. Chance of snow showers.
Temperatures: 23 to 28 deg. F. 12 to 18 deg. F. 27 to 32 deg. F.
Wind Direction: SW W W
Wind Speed: 20 to 30mph. Gusts to 60mph decreasing to 50mph in the afternoon. 20 to 30mph with gusts to 50mph. 20 to 30mph with gusts to 60mph.
Expected snowfall: 6 to 12 in. 3 to 6 in. 1 to 2 in.
For 8000 ft. to 9000 ft.
Sunday Sunday Night Monday
Weather: Cloudy. Snow showers. Cloudy. Snow showers. Mostly cloudy. Chance of snow showers.
Temperatures: 15 to 21 deg. F. 6 to 12 deg. F. 25 to 30 deg. F.
Wind Direction: SW W W
Wind Speed: 30 to 50mph with gusts to 105mph decreasing to 25 to 40mph with gusts to 85mph in the afternoon. 25 to 40mph with guts to 75mph. 30 to 40mph. Gusts to 90mph decreasing to 80mph in the afternoon.
Expected snowfall: 6 to 12 in. 3 to 6 in. 1 to 2 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