THIS AVALANCHE ADVISORY EXPIRED ON March 22, 2016 @ 6:46 am
Avalanche Advisory published on March 21, 2016 @ 6:46 am
Issued by Brandon Schwartz - Tahoe National Forest

MODERATE avalanche danger continues for all elevations and aspects on slopes 35 degrees and steeper. Wind slabs are building in near treeline and above treeline areas on NW-N-NE-E-SE aspects. Rain on snow is keeping the possibility of loose wet avalanche activity ongoing. Increasing avalanche danger will occur this evening through the overnight hours with CONSIDERABLE avalanche danger expected and HIGH avalanche danger possible. The likelihood of natural and human triggered slab avalanches will steadily increase today and tonight.

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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Snow levels are expected to lower today and snowfall intensity is forecast to increase late this afternoon or this evening. This combined with ongoing gale force SW winds will allow wind slabs to continue to build in size and become increasingly widespread near treeline and above treeline on NW-N-NE-E-SE aspects. Existing small wind slabs above 8,000' this morning will become larger as the day progresses. As snow level falls this morning, wind slabs will become more widespread in the 7,000' to 8,000' range. A rapid building of wind slabs is expected this evening during the forecast period of high intensity snowfall.

Areas of potentially unstable wind slabs can be identified and avoided. Look for signs of recent avalanche activity, blowing snow, wind pillows, cornices, and human triggered snow surface cracking. Avoid slopes steeper than 35 degrees where signs of wind slabs are present.

Avalanche Problem 2: Loose Wet
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Rain on snow has created wet surface snow on all aspects below 8,000' to 8,500'. Deep wet snow penetration of skis and snowmobiles is expected to remain ongoing today. Human triggered loose wet avalanche activity will remain possible even as snow level lowers today. Wet snow in the upper portion of the snowpack will take some time to refreeze, remaining loose and wet even after rain changes to snow and air temperatures cool.

Measure penetration into wet snow by stepping off of equipment from time to time today. In areas where body weight penetrates a boot into wet snow up to boot top height or deeper, avoid slopes steeper then 35 degrees and stay out from under steeper slopes above.

recent observations

Observations made yesterday morning on Rubicon Peak (West Shore Tahoe area) and received from yesterday afternoon on Castle Peak (Donner Summit area) revealed a poor to nonexistent overnight snow surface refreeze and deep wet snow. The presence of deep wet snow was directly linked to elevation and changed little by aspect below 8,000'. In the morning hours, conditions remained skier supportable above 8,000' on Rubicon Peak. By the afternoon hours, deep wet snow with ski penetration on 4 to 6 inches was reported from Castle Peak above 8,000'.

Weather and CURRENT CONDITIONS
weather summary

The second wave of the current storm cycle is just offshore this morning and will move through the forecast area today. Snow levels remain in the 7,000' to 8,000' range this morning. Snow level is expected to gradually lower to around 7,000' late this morning and to 6,000' this evening. The majority of snowfall is expected to occur this evening into the nighttime hours, but isolated bands of high intensity snowfall are possible today. Air temperatures have been on a cooling trend overnight, but remain at or a few degrees above freezing at many locations in the 7,000' to 8,700' range. Ridgetop winds remain strong to gale force in speed out of the SW. Gale force wind speed is expected to continue tonight before decreasing to moderate speed tomorrow.

Weather observations from along the Sierra Crest between 8200 ft. and 8800 ft.
0600 temperature: 30 to 35 deg. F.
Max. temperature in the last 24 hours: 38 to 45 deg. F.
Average wind direction during the last 24 hours: SW
Average wind speed during the last 24 hours: 32 mph
Maximum wind gust in the last 24 hours: 69 mph
New snowfall in the last 24 hours: Rain 0.2 to 0.4 inches | Snow 0 to 3 inches
Total snow depth: 75 to 114 inches
Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 7000 ft. to 8000 ft.
Monday Monday Night Tuesday
Weather: Cloudy skies with rain and snow in the morning. Snow in the afternoon. Cloudy skies with snow. Mostly cloudy skies with scattered snow showers.
Temperatures: 36 to 42 deg. F. 18 to 25 deg. F. 25 to 32 deg. F.
Wind Direction: SW SW W
Wind Speed: 25 to 40 mph with gusts to 50 mph. 30 to 40 mph with gusts to 60 mph. 25 to 30 mph with gusts to 40 mph, decreasing to 15 to 20 mph with gusts to 30 mph in the afternoon.
Expected snowfall: Up to 2 in. 3 to 5 in. Up to 1 in.
For 8000 ft. to 9000 ft.
Monday Monday Night Tuesday
Weather: Cloudy skies with a chance of snow in the morning. Snow in the afternoon. Cloudy skies with snow. Mostly cloudy skies with scattered snow showers.
Temperatures: 32 to 38 deg. F. 15 to 22 deg. F. 25 to 31 deg. F.
Wind Direction: SW SW W
Wind Speed: 50 to 70 mph with gusts to 90 mph. Gusts to 105 mph in the afternoon. 45 to 65 mph with gusts to 95 mph. Gusts decreasing to 80 mph after midnight. 40 to 45 mph with gusts to 65 mph, decreasing to 25 to 30 mph with gusts to 45 mph in the afternoon.
Expected snowfall: up to 2 in. 4 to 8 in. Up to 1 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