THIS AVALANCHE ADVISORY EXPIRED ON December 16, 2014 @ 6:48 am
Avalanche Advisory published on December 15, 2014 @ 6:48 am
Issued by Brandon Schwartz - Tahoe National Forest

Isolated pockets of MODERATE avalanche danger may form today near and above treeline on NW-N-NE aspects on slopes 35 degrees and steeper. For all other areas, avalanche danger is LOW. Isolated areas of small and shallow wind slab instability are expected today in wind loaded areas.

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.

1. Low

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Below Treeline
Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.
    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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    Certain
    Very Likely
    Likely
    Possible
    Unlikely
  • Size ?
    Historic
    Very Large
    Large
    Small

Areas of blowing snow will create a fresh round of shallow wind slabs today in near and above treeline areas. These new slabs will deposit on top of older wind slabs that have shown good stability in recent days in all but very isolated areas. Ridgetop winds out of the S to SE rather than the more typical SW will alter the typical pattern of wind slab deposition across slopes to some degree. Winds out of the S to SE will also have better access to old snow on the ground for redistribution than what is available on SW to W aspects. Any avalanche activity that occurs today is expected to be rather small in size. Consequences of triggering an avalanche will be directly tied to interaction with secondary terrain hazards such as rocks, trees, cliffs, and terrain traps.

recent observations

Recent observations from around the forecast area indicate stable snowpack conditions in the vast majority of locations. Evidence of instability has been very isolated over the past few days. Snowpit tests performed yesterday on the crown of the Dec 13 skier triggered avalanche near Elephant's Back (Carson Pass area) indicated that the weak layer of lower density storm snow at the base of the wind slab was still reactive at that location. Otherwise, many slope scale assessments performed in a variety of areas over this past weekend yielded no evidence of instability.

Weather and CURRENT CONDITIONS
weather summary

The first in a series of weak weather systems will move through the forecast area this morning. New snow amounts of up to 3 inches are generally expected today, with a slight chance of receiving 3 to 5 inches. Remote sensors are reporting air temperatures in the 20s this morning at 8,000' to 9,000'. Maximum daytime air temperatures are forecast to reach the mid 20s to low 30s today for areas above 7,000'. Ridgetop winds are out of the south and are moderate in speed. Moderate to strong south to southeast ridgetop winds are forecast for today with gusts to 55 mph.

Weather observations from along the Sierra Crest between 8200 ft. and 8800 ft.
0600 temperature: 21 to 30 deg. F.
Max. temperature in the last 24 hours: 23 to 35 deg. F.
Average wind direction during the last 24 hours: Southwest to South
Average wind speed during the last 24 hours: 22 mph
Maximum wind gust in the last 24 hours: 48 mph
New snowfall in the last 24 hours: 0 to 1 inches
Total snow depth: 22 to 35 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 snow likely in the morning. A chance of snow in the afternoon. Cloudy skies with snow likely. Cloudy skies with a chance of snow showers.
Temperatures: 25 to 32 deg. F. 22 to 26 deg. F. 28 to 33 deg. F.
Wind Direction: SE S shifting to SW after midnight SW
Wind Speed: 15 to 25 mph with gusts to 35 mph. 20 to 25 mph with gusts to 40 mph, shifting and decreasing to 10 to 15 mph with gusts to 25 mph after midnight. 15 to 20 mph with gusts to 30 mph.
Expected snowfall: Up to 3 in. 1 to 4 in. Up to 2 in.
For 8000 ft. to 9000 ft.
Monday Monday Night Tuesday
Weather: Cloudy skies with snow likely in the morning. A chance of snow in the afternoon. Cloudy skies with snow likely. Cloudy skies with a chance of snow showers.
Temperatures: 23 to 28 deg. F. 20 to 23 deg. F. 21 to 29 deg. F.
Wind Direction: S S shifting to SW after midnight SW
Wind Speed: 25 to 35 mph with gusts to 55 mph. 30 to 35 mph with gusts to 55 mph, shifting and decreasing to 20 to 25 mph with gusts to 35 mph after midnight. 20 to 30 mph with gusts to 40 mph.
Expected snowfall: Up to 3 in. 1 to 4 in. Up 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.