THIS AVALANCHE ADVISORY EXPIRED ON February 20, 2017 @ 6:50 am
Avalanche Advisory published on February 19, 2017 @ 6:50 am
Issued by Steve Reynaud - Tahoe National Forest

Moderate avalanche danger exists at all elevations due to wind slab and loose wet avalanche problems.  Human triggered wind slab avalanches remain possible today in near treeline and above treeline terrain.  Loose wet avalanches are possible in below treeline terrain.  Evaluate snow and terrain carefully and make a plan to avoid areas 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: Wind Slab
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Wind slabs will continue to be possible today on NW-N-NE-E-SE aspects in near treeline and above treeline terrain.  Wind slabs will continue to grow with strong to gale force SW winds today.  Look for blowing snow, cornice formation, wind pillows, and snow surface clues to identify where wind slab development is occurring.  Avoid steep wind loaded terrain.

Avalanche Problem 2: Loose Wet
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Loose wet avalanches are possible on all aspects in below treeline areas.  The possibility of light rain and varying cloud cover throughout the forecast area may increase the chances for loose wet avalanches today.  Most of these are expected to be in the form of roller balls but in some areas loose wet avalanches could be large enough to injure or bury a backcountry user.

Look for wet surface snow, roller balls, rain on new snow, and any signs that rapid warming of the snow surface is occurring.  Small terrain traps, such as creeks or gullies, could have big consequences with a small loose wet avalanche.      

recent observations

Observations were made and received yesterday from Stevens Peak (Carson Pass area), Elephants Graveyard (Carson Pass area), Frog Lake Cliffs (Carson Pass area), Granite Chief Peak (Squaw Valley area), Negro Canyon (Donner Summit area), and Mt. Rose.  Skier triggered avalanches were reported at Frog Lake Cliffs, Granite Chief Peak, and Negro Canyon.  An avalanche airbag was deployed to avoid a potential burial at Frog Lake Cliffs.  This avalanche was on a NE aspect, near 9000', 1' deep, on a 40 degree convex rollover.  Strong to gale force SW winds were reported area wide with snow transport occurring.  Most avalanches observed yesterday were wind slabs, but loose wet and storm slab avalanches were also reported.

Weather and CURRENT CONDITIONS
weather summary

Bands of light snow and rain will be mostly limited to areas near the Sierra Crest today with little to no accumulation.  Strong SW winds will continue today and increase into the afternoon ahead of our next storm system.  A strong atmospheric river is forecasted to make a direct hit to the Sierra bringing extreme amounts of rain and high elevation snow, similar to some of the largest AR systems we have experienced this year.  Snow levels are forecasted to be at 7000-7500' for most of Monday before dropping down Tuesday morning.  Multiple feet of snow could be possible at the higher elevations with 3-6'' of rain at the lower elevations.  A winter storm warning is in effect from 10pm Sunday night to 4am Tuesday morning.  An active weather pattern could continue with colder storms bringing snow from Tuesday through the weekend.

Weather observations from along the Sierra Crest between 8200 ft. and 8800 ft.
0600 temperature: 20 to 26 deg. F.
Max. temperature in the last 24 hours: 38 deg. F.
Average wind direction during the last 24 hours: SW
Average wind speed during the last 24 hours: 35 to 45 mph
Maximum wind gust in the last 24 hours: 87 mph
New snowfall in the last 24 hours: Trace to 1 inches
Total snow depth: 120 to 141 inches
Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 7000 ft. to 8000 ft.
Sunday Sunday Night Monday
Weather: Mostly cloudy. Chance of snow. Cloudy. Snow through the night, rain after midnight. Cloudy. Rain and snow. Snow level above 7500'.
Temperatures: 35 to 40 deg. F. 29 to 34 deg. F. 37 to 42 deg. F.
Wind Direction: SW SW SW
Wind Speed: 15 to 25mph. Gusts up to 35mph increasing to 50mph in the afternoon. 15 to 25mph with gusts to 50mph. 20 to 35mph. Gusts up to 70mph increasing to 85mph in the afternoon.
Expected snowfall: Up to 2 in. 3 to 7 in. 10 to 20 in.
For 8000 ft. to 9000 ft.
Sunday Sunday Night Monday
Weather: Mostly cloudy. Chance of snow. Cloudy. Snow likely in the evening, then snow likely after midnight. Cloudy. Snow.
Temperatures: 33 to 38 deg. F. 27 to 32 deg. F. 33 to 38 deg. F.
Wind Direction: SW SW SW
Wind Speed: 20 to 35mph with gusts to 60mph increasing to 30 to 45mph with gusts to 80mph in the afternoon. 30 to 50mph. Gusts to 80mph increasing to 105mph after midnight. 40 to 60mph with gusts to 135mph.
Expected snowfall: Up to 2 in. 4 to 8 in. 14 to 24 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