THIS AVALANCHE ADVISORY EXPIRED ON February 27, 2014 @ 6:59 am
Avalanche Advisory published on February 26, 2014 @ 6:59 am
Issued by Brandon Schwartz - Tahoe National Forest

During daylight hours, avalanche danger is expected to remain LOW for all elevations and aspects. As snowfall intensity increases tonight, a significant increase in avalanche danger will occur with natural avalanche activity possible.

1. Low

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Above Treeline
Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.

1. Low

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Near Treeline
Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.

1. Low

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Below Treeline
Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.
    Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.
Avalanche Problem 1: Normal Caution
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During the day today, avalanche concerns are few. Cloud cover built slowly last night and is expected to have allowed wet snow from yesterday a chance to refreeze. Precipitation rates today are expected to be light with new snow amounts of up to 1 inch forecast to accumulate during daylight hours. Significant avalanche problems of wind slabs and storm slabs are not expected to form until tonight.

Avalanche Problem 2: Wind Slab
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After snowfall intensity increases tonight, natural and human triggered wind slab avalanches will become possible near and above treeline on NW-N-NE-E-SE aspects.

Avalanche Problem 3: Storm Slab
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After snowfall intensity increases tonight, natural and human triggered storm slab avalanches will become possible. Areas where weak faceted snow exists at the old snow snow surface may cause new snow to bond poorly. In general snowpack failure is expected to occur at or above the old/new snow interface.

recent observations

In general the existing snowpack is in good condition to handle new snow loading. A few specific areas with weak faceted snow at the current snow surface that will become the old/new snow interface have been observed.

Observations made yesterday on Lincoln Ridge (Yuba Pass area) revealed that the snow surface on north aspects below treeline that were sheltered from both sun and wind held up to 3 inches of near surface facets. These weak facets were sitting on top of a very thick, strong, and supportable rain crust. With a new slab of storm snow expected tonight, the possibility exists for a developing slab/weak layer/bed surface combination for storm slabs in below treeline terrain.

Other recent observation on Round Top Peak (Carson Pass area) and on Powderhouse Peak (Luther Pass area) noted that northerly aspect bed surfaces from slab avalanche activity Feb 8-9 hold several layers of weak faceted snow. With no overlying slab at this time, there is no current instability issue. As a slab of new snow is placed on top of these weak layers tonight, slab avalanche problems may arise.

Weather and CURRENT CONDITIONS
weather summary

Pacific moisture is streaming into the west coast. Cloud cover has increased overnight. Light precipitation is expected to begin after 10 am with snow level expected at 6,500' to 7,000' this afternoon. Snow level is forecast to fall during the overnight hours. The period of highest intensity snowfall is expected to occur tonight between 10 pm and 4 am. New snow amounts of 10 to 18 inches above 7,000' are expected with the greatest accumulations occurring along the Sierra Crest south of Hwy 50. During the day today, ridgetop winds are forecast out of the south to southwest. Moderate wind speeds are expected to increase as the day progresses with gusts up to 50 mph.

Weather observations from along the Sierra Crest between 8200 ft. and 8800 ft.
0600 temperature: 31 to 36 deg. F.
Max. temperature in the last 24 hours: 43 to 50 deg. F.
Average wind direction during the last 24 hours: South
Average wind speed during the last 24 hours: 18 mph
Maximum wind gust in the last 24 hours: 37 mph
New snowfall in the last 24 hours: 0 inches
Total snow depth: 35 to 44 inches
Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 7000 ft. to 8000 ft.
Wednesday Wednesday Night Thursday
Weather: Cloudy skies with a slight chance of snow in the morning. Snow likely and a chance of rain in the afternoon. Cloudy skies with rain in the evening. Snow through the night. Cloudy skies becoming mostly cloudy. Snow in the morning. Snow likely during the afternoon.
Temperatures: 36 to 43 deg. F. 19 to 26 deg. F. 29 to 36 deg. F.
Wind Direction: Southwest Southwest Southwest
Wind Speed: 15 to 25 mph with gusts to 35 mph. 25 to 30 mph with gusts to 45 mph. 20 to 30 mph with gusts to 45 mph.
Expected snowfall: Up to 1 in. 8 to 12 in. 3 to 5 in.
For 8000 ft. to 9000 ft.
Wednesday Wednesday Night Thursday
Weather: Cloudy skies. Snow likely in the afternoon. Cloudy skies with snow. Cloudy skies becoming mostly cloudy. Snow in the morning. Snow likely during the afternoon.
Temperatures: 36 to 42 deg. F. 15 to 22 deg. F. 30 to 36 deg. F.
Wind Direction: South South Southwest
Wind Speed: 20 to 30 mph with gusts to 50 mph. 40 to 50 mph with gusts to 80 mph. 35 to 45 mph with gusts to 80 mph.
Expected snowfall: Up to 1 in. 8 to 12 in. 3 to 5 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.