THIS AVALANCHE ADVISORY EXPIRED ON March 1, 2015 @ 7:00 am
Avalanche Advisory published on February 28, 2015 @ 7:00 am
Issued by Andy Anderson - Tahoe National Forest

MODERATE avalanche danger exists on slopes 35 degrees and steeper at all elevations and on all aspects today due to newly formed wind slabs, storm slabs, and some persistent slabs. The NW-N-NE-E-SE aspects represent the best places to trigger an avalanche since more than one avalanche problem may exist on those aspects. Evaluate snow and terrain carefully to make backcountry travel decisions. Human triggered avalanches are possible today.

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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Human triggered wind slab avalanches will be possible today. Expect to find wind slabs on the near and above treeline wind-loaded and cross-loaded NW-N-NE-E-SE aspects today. Since the winds shifted between the W and SW, some cross-loading may have occurred on some S facing slopes as well. These winds slabs have formed on top of frozen crusts and may not have bonded to the old snow surfaces very well. Most of these slabs should measure 1-3 ft. in depth with some smaller or larger ones scattered across the region depending on the amount of new snow that fell in a particular area.

Avalanche Problem 2: Storm Slab
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Some human triggered storm slab avalanches may also be possible today on any slopes that had previous snow cover. Like the wind slabs mentioned above, these storm slabs will vary in depth depending on how much snow a specific location received and could range from a few inches to a foot in depth. They have formed above frozen crusts in most areas and have not had time to form good bonds with the old snow surfaces. In addition to the possiblity of storm slabs, some loose snow sluffing may also occur on steep slopes today.

Avalanche Problem 3: Persistent Slab
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Prior to this storm, near surface facets existed on isolated near and below treeline NW-N-NE wind sheltered and shaded slopes above 8000 ft. This soft weak layer of snow rests above a frozen rain crust that could serve as an efficient bed surface for snow to slide on. Prior to the storm, the only avalanche ingredient missing was a slab on top of the weak layer/bed surface combination. The new snow deposited by this storm has the potential to be that slab. In areas where the new snow has accumulated above the persistent weak layer of near surface facets (soft weak sugary snow), human triggered persistent slab avalanches may be possible today. These kind of avalanches tend to release farther away from the person who triggers them often times causing the slope above them to release.

recent observations

Yesterday on Incline Lake Peak, the snow surface consisted of a mix of skier scrapped crusts, thin melt-freeze crusts, and small patches of soft weak near surface facets. On the northerly aspects where the patches of near surface facets existed, they rested above a frozen crust in the upper snowpack. During the morning a small snow shower dropped .5 to .75 in. of new snow, and this new snow had trouble bonding to the old snow surfaces. Ski cuts on steep test slopes caused it to sluff off of the crusts. 

Weather and CURRENT CONDITIONS
weather summary

5 to 8 inches of snow has accumulated across the forecast area since yesterday. Most of this snow fell during the night and accumulations vary from one place to another due to the showery nature of the snow fall. The snow showers should continue today, and the forecast calls for another 2 to 5 inches above 7000 ft. with an additional 1 to 3 inches at lake level. By this afternoon some thunderstorms may become possible. Snow showers should start to become more scattered and isolated during the next 24 hours as the low pressure system continues southward. By tomorrow the forecast calls for a few lingering isolated snow showers and up to 1 more inch of snow in a few places. The moderate west and southwest winds have started to decrease and should continue to calm down today before they shift to the northeast tonight. Light northeast winds should persist through tomorrow. Temperatures should remain cold today with daytime highs in the 20's above 7000 ft. Temperatures should warm up few degrees tomorrow into the upper 20's and low 30's.

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: 27 to 34 deg. F.
Average wind direction during the last 24 hours: West to southwest
Average wind speed during the last 24 hours: 20 to 30 mph
Maximum wind gust in the last 24 hours: 47 mph
New snowfall in the last 24 hours: 5 to 8 inches
Total snow depth: 34 to 48 inches
Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 7000 ft. to 8000 ft.
Saturday Saturday Night Sunday
Weather: Cloudy with snow showers. Isolated thunderstorms possible in the afternoon Mostly cloudy with snow showers in the evening. Snow showers becoming scattered after midnight Partly cloudy with isolated snow showers
Temperatures: 23 to 30 deg. F. 13 to 20 deg. F. 26 to 33 deg. F.
Wind Direction: Variable Northeast Northeast
Wind Speed: Light 0 to 5 mph increasing to 10 to 15 mph with gusts to 25 mph after midnight 10 to 15 mph
Expected snowfall: 1 to 4 in. up to 1 in. up to 1 in.
For 8000 ft. to 9000 ft.
Saturday Saturday Night Sunday
Weather: Cloudy with snow showers. Isolated thunderstorms possible in the afternoon Mostly cloudy with snow showers in the evening. Snow showers becoming scattered after midnight Partly cloudy with isolated snow showers
Temperatures: 22 to 28 deg. F. 15 to 21 deg. F. 25 to 31 deg. F.
Wind Direction: West Northeast Northeast
Wind Speed: 10 to 15 mph in the morning decreasing in the afternoon 15 to 20 mph with gusts to 30 mph 10 to 15 mph
Expected snowfall: 2 to 5 in. 1 to 2 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.