THIS AVALANCHE ADVISORY EXPIRED ON February 1, 2016 @ 6:48 am
Avalanche Advisory published on January 31, 2016 @ 6:48 am
Issued by Brandon Schwartz - Tahoe National Forest

Upper end MODERATE avalanche danger exists today for all elevations and aspects on slopes 35 degrees and steeper due to a combination of newly formed wind slab, storm slab, and loose dry avalanche problems. Natural avalanche activity in not expected today, but isolated natural activity is certainly not out of the question. Human triggered avalanches are expected today and should not be a surprise to backcountry travelers.

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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A new round of wind slab development occurred last night and will continue to occur with ongoing SW to NW wind and snowfall today. These new wind slabs are depositing on top of lower density, minimally wind effected snow that existed at the snow surface yesterday. This will create easily identifiable strong over weak snow layering in areas where problematic wind slabs have formed. Shifting winds last night and today will expand the range of aspects, enhance wind slab layering, and create some wind slabs in less typical areas. Areas of cornice formation, wind pillows, and snow surface texture will provide clues for suspect slopes in near and above treeline terrain on NW-N-NE-E-SE-S aspects today. Wind slabs may be easier to trigger today than yesterday. If in doubt, stay on slopes less than 32 degrees in slope angle without steeper terrain above.

Avalanche Problem 2: Storm Slab
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As multiple layers of recent storm snow stack up in wind protected areas below treeline, subtle differences between the snow in each layer may lead to storm slab development on all aspects. Human triggered snow surface cracking in wind protected areas is an indication that unstable storm slabs exist in the area. Staying on slopes less than 32 degrees in slope angle without steeper terrain above is an effective way to avoid this avalanche problem.

Avalanche Problem 3: Loose Dry
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In wind protected areas below treeline where no signs of storm slab instability exist, loose dry avalanches will be the more likely instability in steep terrain. If choosing to push the risk and venture onto slopes steeper than 35 degrees, evaluate the terrain for secondary hazards such as terrain traps, rocks, trees, and cliffs below that could greatly magnify the consequences of being pushed off line by a loose dry avalanche.

recent observations

Observations made yesterday on Tamarack Peak and received from Mt. Baldy (both in the Mount Rose area) indicated that wind slab instability yesterday was small and isolated. One very small skier triggered wind slab avalanche was observed on the Far East Ridge of Tamarack Peak on N aspect in near treeline terrain. Some natural cornice collapse and a possible small wind slab avalanche crown line was observed on a wind loaded E aspect on the south ridge of Rose Knob Peak.

Snowpit work on Tamarack Peak near treeline on an E aspect at 9,675' indicated a potential weak layer with propagation characteristics along the bottom of the rain crust that exits at the old snow/new snow interface from the Jan 29-Jan 30 snowfall. In this area, the rain crust was found around 1.5 feet below the snow surface all the way up to the summit at 9,900'. By late this afternoon this rain crust may be closer to 2.5 feet below the snow surface in areas above 8,500'.

Weather and CURRENT CONDITIONS
weather summary

Another storm system is moving through the forecast area. New snow amounts from the last 12 hours are in the 4 to 6 inch range across the forecast area. Another 3 to 5 inches is expected today. Today's maximum daytime air temperatures are expected in the mid teens to mid 20s for areas above 7,000'. Ridgetop winds shifted from SW to S last night, coinciding with much of the snowfall. Winds are expected to shift back to the SW this morning and are forecast to shift to the W to NW this afternoon and on to the NW to N tonight. Moderate speed winds with a decreasing trend is expected this afternoon. A strong N to NE wind event is forecast for tonight and tomorrow.

Weather observations from along the Sierra Crest between 8200 ft. and 8800 ft.
0600 temperature: 18 to 22 deg. F.
Max. temperature in the last 24 hours: 24 to 32 deg. F.
Average wind direction during the last 24 hours: SW
Average wind speed during the last 24 hours: 25 mph
Maximum wind gust in the last 24 hours: 44 mph
New snowfall in the last 24 hours: 4 to 6 inches
Total snow depth: 72 to 85 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 skies with snow. Cloudy skies with snow likely. Mostly cloudy skies with a slight chance of snow showers in the morning.
Temperatures: 18 to 25 deg. F. 9 to 15 deg. F. 18 to 25 deg. F.
Wind Direction: SW shifting to NW N N
Wind Speed: 15 to 20 mph with gusts to 30 mph. 20 to 30 mph with gusts to 40 mph. 20 to 30 mph with gusts to 40 mph. Gusts increasing to 50 mph in the afternoon.
Expected snowfall: 3 to 5 in. 2 to 3 in. 0 to trace in.
For 8000 ft. to 9000 ft.
Sunday Sunday Night Monday
Weather: Cloudy skies with snow. Cloudy skies with snow likely. Mostly cloudy skies with a slight chance of snow showers in the morning.
Temperatures: 13 to 20 deg. F. 3 to 10 deg. F. 14 to 21 deg. F.
Wind Direction: SW to W NW to N N
Wind Speed: 25 to 30 mph with gusts to 45 mph, shifting and decreasing to 10 to 15 mph with gusts to 25 mph in the afternoon. 30 to 35 mph with gusts to 55 mph, increasing to 40 to 45 mph with gusts to 65 mph after midnight. 35 to 40 mph with gusts to 60 mph, increasing to 45 to 50 mph with gusts to 70 mph in the afternoon.
Expected snowfall: 3 to 5 in. 2 to 3 in. 0 to trace 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.