THIS AVALANCHE ADVISORY EXPIRED ON February 26, 2017 @ 7:00 am
Avalanche Advisory published on February 25, 2017 @ 7:00 am
Issued by Andy Anderson - Tahoe National Forest

Human triggered wind slab avalanches and small loose snow sluffs will remain possible today. MODERATE avalanche danger exists in near and above treeline terrain today with LOW danger in below treeline areas. Carefully evaluate snowpack and terrain before committing to any slopes and identify where avalanche problems may exist. Use this information to avoid slopes where avalanche problems may exist.

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.

1. Low

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Below Treeline
Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.
    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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Increased winds today combined with soft snow on many windward aspects means another round of wind-loading and wind slab formation. Human-triggerable wind slab avalanches will remain possible in near and above treeline terrain today. These could include larger wind slabs formed by SW winds lingering on NW-N-NE-E-SE-S aspects that may grow larger today due to additional loading. Wind slabs formed by NW, NE, and SE winds in the last 24 to 36 hours could exist on all other aspects as well. Many of wind slabs should remain smaller and exist near ridgelines, but some could be large enough to bury or injure backcountry travelers. The most fragile wind slabs will exist in the places most exposed to wind-loading and in terrain like gullies, couloirs, unsupported slopes above cliffs, and other steep, complex, and wind-loaded terrain.

Use clues such as blowing snow, cornice formations, and wind pillows to help identify recently wind-loaded slopes where unstable wind slabs may exist. Then use this information to plan a backcountry travel route that avoids the potentially unstable wind slabs and utilizes more sheltered terrain where better snow for recreation will exist.

Avalanche Problem 2: Loose Dry
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Some small and mostly inconsequential loose snow sluffs could still remain possible on steep sheltered slopes. Most of these would occur where the coldest and least cohesive snow exists on NW-N-NE aspects

recent observations

A snowmobile avalanche class reported seeing a recent wind slab avalanche in the Blue Lakes area that may have occurred yesterday on an E facing aspect at 8200 ft, and they reported seeing significant wind transport in that area yesterday. Observations from Andesite Peak, Negro Canyon, Ophir Peak, and Blackwood Ridge all found soft unconsolidated snow on sheltered W-NW-N-NE-E aspects and a mix of wind-affected snow including firm wind-packed snow, wind scoured surfaces, and soft wind slabs on exposed near and above treeline slopes. Tests and observations in most of these places did not reveal many signs of instability on sheltered slopes. Cornices above test slopes in Negro Canyon still broke easily and well away from their edges. Some small skier-triggered cracking occurred near the ridgeline on Ophir Peak, and one isolated whumpf occurred on Andesite Peak. Ski cuts on steep E-NE-N facing slopes in Negro Canyon did release small loose dry sluffs that entrained the top 4-5 inches of snow. 

Weather and CURRENT CONDITIONS
weather summary

A weak low-pressure system moving south through the forecast area today will bring increased cloud cover, winds, and some light snow showers. Most of the precipitation associated with this system should stay west of the Sierra Crest but some areas could see up an inch of snow, especially north of I80. After a break in the weather tonight another weak but slightly stronger winter storm will push into the region for Sunday afternoon through Monday morning. Temperatures should remain cold through these storms. 

Weather observations from along the Sierra Crest between 8200 ft. and 8800 ft.
0600 temperature: 11 to 17 deg. F.
Max. temperature in the last 24 hours: 20 to 26 deg. F.
Average wind direction during the last 24 hours: Southwest to southeast
Average wind speed during the last 24 hours: 25 to 40 mph
Maximum wind gust in the last 24 hours: 67 mph
New snowfall in the last 24 hours: 1 inches
Total snow depth: 143 to 190 inches
Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 7000 ft. to 8000 ft.
Saturday Saturday Night Sunday
Weather: Mostly cloudy with scattered snow showers and increasing clouds in the afternoon Mostly cloudy with snow showers in the evening. Snow showers becoming isolated after midnight. Mostly cloudy with a slight chance of snow showers in the afternoon
Temperatures: 23 to 28 deg. F. 11 to 16 deg. F. 26 to 31 deg. F.
Wind Direction: Southwest and southeast Variable Southwest
Wind Speed: 10 to 15 mph Light Light in the morning increasing to 20 to 30 mph with gusts to 60 mph in the afternoon
Expected snowfall: up to 1 in. up to 1 in. 0 in.
For 8000 ft. to 9000 ft.
Saturday Saturday Night Sunday
Weather: Mostly cloudy with scattered snow showers and increasing clouds in the afternoon Mostly cloudy with snow showers in the evening. Snow showers becoming isolated after midnight. Mostly cloudy with a slight chance of snow showers in the afternoon
Temperatures: 18 to 23 deg. F. 10 to 15 deg. F. 22 to 27 deg. F.
Wind Direction: Southwest Variable Southwest
Wind Speed: 20 to 30 mph with gusts to 50 mph in the morning becoming 10 to 15 mph with gusts to 30 mph in the afternoon Light 15 to 20 mph with gusts to 45 mph increasing to 30 to 50 mph with gusts to 90 mph in the afternoon
Expected snowfall: up to 1 in. up to 1 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