THIS AVALANCHE ADVISORY EXPIRED ON March 27, 2014 @ 7:00 am
Avalanche Advisory published on March 26, 2014 @ 7:00 am
Issued by Andy Anderson - Tahoe National Forest

CONSIDERABLE danger exists on slopes 35 degrees and steeper on wind loaded NW-N-NE-E-SE aspects in near and above treeline terrain. MODERATE avalanche danger exists in all other areas. Human triggered wind slab avalanches are likely today and storm slab avalanches are possible.

After 2 weeks of stable melt-freeze conditions, today represents a day when natural and human triggered avalanches could occur. Don't let excitement over the return of winter and/or "powder fever" override good judgment and thoughtful and safe backcountry decision making.

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.

2. Moderate

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Below Treeline
Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.
    Dangerous avalanche conditions. Careful snowpack evaluation, cautious route-finding and conservative decision-making essential.
Avalanche Problem 1: Wind Slab
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Human triggered wind slab avalanches are likely today and natural wind slab avalanches may become possible. New snow and southwest winds created new wind slabs on the wind-loaded aspects last night. As the snow and wind continue today these wind slabs will become more widespread and larger. In exposed near and above treeline terrain, fragile wind slabs 2 to 3 ft in depth could exist on the wind loaded N-NE-E aspects and cross loaded NW and SE aspects by this afternoon. In areas where more or less snow falls than forecasted the winds slabs could either be larger or smaller.

Avalanche Problem 2: Storm Slab
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Human triggered storm slab avalanches will become possible today due to an increase in snowfall intensity and fluctuating snow levels. This combination will allow heavier layers of storm snow to form above lighter layers of storm snow. In addition the changing conditions during the storm could also allow other storm snow weakness to form within the storm snow. The easiest places to trigger these storm slabs will be on the sheltered northerly aspects above 8000 ft. that held thin breakable crusts prior to the storm, but fragile storm slabs resting on firm crusts could exist on any slope that had previous snow cover.

recent observations

Observations on Becker Ridge yesterday remained consistent with data collected from around the region during the last 10 days. Stable melt-freeze conditions existed on the southerly aspects, and a well consolidated snowpack existed on the northerly aspects. The observations and data did not indicate lurking instabilities below the surface of the old snow. However, the surface conditions that consisted of a myriad of smooth crusts, scoured surfaces, and some thin breakable crusts with soft snow just below them could represent great bed surfaces for avalanches to run on and/or surfaces that may be difficult for new snow to bond with.

Weather and CURRENT CONDITIONS
weather summary

Yesterday evening snow levels started around 6700 ft. and fell to below lake level during the night. Most places above 7000 ft. received 4-5 inches of new snow last night with a few remote sensors south of Hwy 50 showing up to 8 inches of new snow. Below 7000 ft. most sensors only indicated 1 to 2 inches. Wind sensors recorded strong southwest winds averaging 35 to 50 mph. The heaviest snowfall and strongest winds should occur today as the main part of the storm impacts the forecast area. The forecast calls for most areas above 7000 ft. to receive another 4 to 8 inches of snow by midnight with up to a foot possible along the Sierra Crest during that time. Due to the disorganized and convective nature of this storm snowfall amounts could vary from place to place with some areas seeing more or less snow than forecasted. Snow levels could also rise today and the forecast calls for them to fluctuate between 6000 and 7000 ft. during the day. By tomorrow the storm should begin to dissipate with the forecast calling for a decrease in cloud cover, decrease in wind speed, a change of wind directions towards the northwest, and only a chance of snow showers.

Weather observations from along the Sierra Crest between 8200 ft. and 8800 ft.
0600 temperature: 18 to 24 deg. F.
Max. temperature in the last 24 hours: 34 to 42 deg. F.
Average wind direction during the last 24 hours: Southwest
Average wind speed during the last 24 hours: 35 to 50 mph
Maximum wind gust in the last 24 hours: 89 mph
New snowfall in the last 24 hours: 4 to 8 inches
Total snow depth: 38 to 48 inches
Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 7000 ft. to 8000 ft.
Wednesday Wednesday Night Thursday
Weather: Snow Snow Cloudy becoming mostly cloudy. Chance of snow showers
Temperatures: 28 to 34 deg. F. 19 to 24 deg. F. 28 to 34 deg. F.
Wind Direction: Southwest Southwest Southwest
Wind Speed: 20 to 35 mph with gusts to 50 mph 20 to 35 mph with gusts to 50 mph 20 to 35 mph with gusts to 55 mph decreasing to 15 to 25 mph with gusts to 40 mph in the afternoon
Expected snowfall: 3 to 6 in. 1 to 3 in. 0 to 1 in.
For 8000 ft. to 9000 ft.
Wednesday Wednesday Night Thursday
Weather: Snow Snow Cloudy becoming mostly cloudy. Chance of snow showers
Temperatures: 23 to 30 deg. F. 14 to 21 deg. F. 24 to 31 deg. F.
Wind Direction: Southwest Southwest West shifting to the northwest in the afternoon
Wind Speed: 30 to 50 mph with gusts 60 to 80 mph 25 to 45 mph with gusts 60 to 80 mph 25 to 45 mph with gusts to 60 to 80 mph decreasing to 20 to 35 mph with gusts to 55 mph in the afternoon
Expected snowfall: 4 to 8 in. 2 to 4 in. 0 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.