THIS AVALANCHE ADVISORY EXPIRED ON March 15, 2016 @ 6:50 am
Avalanche Advisory published on March 14, 2016 @ 6:50 am
Issued by Brandon Schwartz - Tahoe National Forest

Areas of CONSIDERABLE avalanche danger are expected today near treeline and above treeline on NW-N-NE-E-SE aspects on slopes 35 degrees and steeper due to ongoing wind slab problems. For all other areas, MODERATE avalanche danger exists on slopes 35 degrees and steeper due to potential storm slabs. Loose wet avalanche problems may or may not develop this afternoon on E-SE-S-SW-W aspects depending on cloud cover. Natural and human triggered avalanches remain possible to likely today.

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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Wind slab avalanches occurred yesterday. Continued gale force SW to W winds are scouring all snow available for transport and creating wind loading and ongoing wind slab formation in lee areas. The vast majority of wind slabs are expected near treeline and above treeline on NW-N-NE-E-SE aspects. Due to the strength of the winds, some wind slabs may exist in below treeline areas as well. A few isolated slabs may form on the generally windward S-SW-W aspects as winds wrap around localized terrain features.

Identify and avoid steep wind loaded terrain. Use clues such as recent avalanche activity, test slope failures, blowing snow, cornice formations, wind pillows, and shooting cracks to determine where wind slabs exist. Avoid slopes 35 degrees and steeper that hold wind slabs.

Avalanche Problem 2: Storm Slab
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New snow that fell yesterday and last night in wind protected areas below treeline may contain weak layers within the storm snow. In the case that any unstable weak layers did form, storm slabs will be a problem on slopes steeper than 35 degrees. Use clues such as recent avalanche activity, test slope failures, and shooting cracks to determine if storm slabs are present. Avoid slopes steeper than 35 degrees when signs of instability exist.

Avalanche Problem 3: Loose Wet
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Depending on the amount of cloud cover clearing that occurs during the mid day and afternoon hours, loose wet avalanches may or may not become a problem today. If skies clear and air temperatures warm, significant roller ball and pinwheel activity is expected. This will be a precursor to loose wet avalanche activity that could be either natural or human triggered. The vast majority of wet snow instability is expected on E-SE-S-SW-W aspects. Wet snow instablility could occur on NW-N-NE aspects as well in sun exposed and/or lower elevation areas.

recent observations

Observations made and received yesterday from the Donner Summit, Mount Rose, Pole Creek, and Carson Pass areas revealed a wide range of instability. In the Donner Summit and Carson Pass areas, signs of instability were widespread with natural and human triggered wind slab avalanches occurring. Skier triggered shooting cracks and snowpack collapse were noted in both wind loaded and wind protected areas. Snowpit tests yielded very unstable results. At the other end of the spectrum in the Pole Creek and Mount Rose areas, signs of instability were limited to the presence of significant amounts of new snow and wind loading. Visibility was poor, but no avalanche activity was seen in these areas and snowpit tests did not produce problematic signs of instability. See below for video, photos, and more info.

Weather and CURRENT CONDITIONS
weather summary

Precipitation is winding down and the storm system is exiting the region this morning. Storm totals above 7,000' since Saturday range from 20 to 50 inches by location. Over the past 12 hours, snow level rose to 6,500' to 7,000' with 7 to 14 inches of new snow accumulated above 7,000'. Ridgetop winds remain gale force out of the SW this morning and are forecast to remain that way through today. Winds are expected to decrease to moderate to strong in speed tonight and to moderate speed tomorrow. Air temperatures at the mid and upper elevations are a few degrees below freezing this morning. Air temperatures are on a slight cooling trend after having warmed a few degrees during the overnight hours. Maximum daytime air temperatures above 7,000' are forecast to reach the upper 20s to low 40s today. There is significant uncertainty as to how quickly skies will clear this afternoon. Mostly cloudy to very sunny conditions are possible.This will play a significant role in how much warming occurs today.

Weather observations from along the Sierra Crest between 8200 ft. and 8800 ft.
0600 temperature: 25 to 30 deg. F.
Max. temperature in the last 24 hours: 29 to 33 deg. F.
Average wind direction during the last 24 hours: SW
Average wind speed during the last 24 hours: 55 mph
Maximum wind gust in the last 24 hours: 108 mph
New snowfall in the last 24 hours: 12 to 20 inches
Total snow depth: 91 to 124 inches
Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 7000 ft. to 8000 ft.
Monday Monday Night Tuesday
Weather: Mostly cloudy skies. Possibly becoming sunny. Snow showers in the morning. A slight chance of snow showers in the afternoon. Mostly cloudy skies. Partly cloudy skies.
Temperatures: 35 to 41 deg. F. 16 to 23 deg. F. 39 to 45 deg. F.
Wind Direction: SW to W SW to W SW
Wind Speed: 35 to 50 mph decreasing to 25 to 40 mph in the afternoon. Gusts up to 70 mph in the morning. 20 to 30 mph with gusts to 40 mph. 15 to 25 mph with gusts to 35 mph.
Expected snowfall: Up to 1 in. 0 in. 0 in.
For 8000 ft. to 9000 ft.
Monday Monday Night Tuesday
Weather: Mostly cloudy skies. Possibly becoming sunny. Snow showers in the morning. A slight chance of snow showers in the afternoon. Mostly cloudy skies. Partly cloudy skies.
Temperatures: 28 to 35 deg. F. 16 to 23 deg. F. 35 to 41 deg. F.
Wind Direction: SW to W SW to W SW to W
Wind Speed: 50 to 65 mph with gusts to 100 mph. 40 to 50 mph with gusts to 75 mph, decreasing to 30 to 35 mph with gusts to 55 mph after midnight. 20 to 30 mph with gusts to 45 mph.
Expected snowfall: Up to 1 in. 0 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