Avalanche Advisory published on December 21, 2014 @ 6:22 am
This advisory is valid for 24 hours
Issued by Brandon Schwartz - Tahoe National Forest
bottom line

Near and above treeline, pockets of MODERATE avalanche danger remain on NW-N-NE-E aspects on slopes 35 degrees and steeper due to ongoing concern for human triggered wind slabs. For all other areas, avalanche danger in LOW.

How to read the advisory


Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern. Natural avalanches unlikely; human-triggered avalanches possible. Small avalanches in specific areas; or large avalanches in isolated areas.

avalanche danger

How to read the advisory

2. Moderate

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Above Treeline

2. Moderate

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Near Treeline

1. Low

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Below Treeline

Near and above treeline, pockets of MODERATE avalanche danger remain on NW-N-NE-E aspects on slopes 35 degrees and steeper due to ongoing concern for human triggered wind slabs. For all other areas, avalanche danger in LOW.

Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern. Natural avalanches unlikely; human-triggered avalanches possible. Small avalanches in specific areas; or large avalanches in isolated areas.
weather

Warm air pushed into the forecast area yesterday afternoon and last night. Remote sensors are reporting air temperatures this morning between 8,000' and 9,000' in the mid 30s. Snow level has risen to 7,700' to 8,500'. Air temperatures will remain warm and snow levels high today. A slight chance of light rain and snow will taper off as the day progresses. Ridgetop winds have remained strong out of the southwest to west and will continue through tonight. Strong N to NE winds are forecast for tomorrow. Building high pressure will allow for decreasing cloud cover over the next 24 hours.

recent observations

Observations made yesterday on Tamarack and Incline Lake Peaks (Mount Rose area) and received from Castle Peak (Donner Summit area) revealed significant amounts of ongoing wind transport in near and above treeline areas. In wind loaded areas, skier triggered cracking up to 10 feet was created on test slopes below cornice features. In a few cases, small wind slabs 6 to 14 inches deep were released. In all cases the weak layer was an easily identifiable lower density layer of recent storm snow at the base of the surface wind slab. No signs of instability were observed in wind protected areas.

Avalanche Problem 1:   Wind Slab
  • Type ?
  • Aspect/Elevation ?
  • Likelihood ?
    likely
    unlikely
  • Size ?
    large
    small
  • Trend ?
    Decreasing Danger

Human triggered wind slabs remain an ongoing avalanche problem. Strong winds over the past two days have kept wind transport ongoing, despite decreasing snowfall amounts. Winds slabs are expected to be more difficult to trigger today than yesterday. Heavily wind loaded slopes directly below cornice features represent the most likely place to trigger an avalanche at this time.

CURRENT CONDITIONS  Weather observations from along the Sierra Crest between 8200 ft. and 8800 ft.
0600 temperature: 32 to 37 deg. F.
Max. temperature in the last 24 hours: 32 to 37 deg. F.
Average wind direction during the last 24 hours: West Southwest
Average wind speed during the last 24 hours: 39 mph
Maximum wind gust in the last 24 hours: 63 mph
New snowfall in the last 24 hours: 0 to trace inches
Total snow depth: 27 to 39 inches
Two-Day Mountain Weather Forecast  Produced in partnership with the Reno NWS
For 7000 ft. to 8000 ft.
  Today Tonight Monday
Weather: Mostly to partly cloudy skies with a slight chance of rain. Partly cloudy skies. Partly cloudy skies, becoming sunny.
Temperatures: 40 to 47 deg. F. 27 to 34 deg. F. 40 to 47 deg. F.
Wind direction: W NW NW shifting to NE
Wind speed: 10 to 20 mph with gusts to 40 mph. 5 to 15 mph. 5 to 15 mph with gusts to 30 mph.
Expected snowfall: 0 in. 0 in. 0 in.
For 8000 ft. to 9000 ft.
  Today Tonight Monday
Weather: Mostly to partly cloudy skies with a slight chance of rain and snow. Partly cloudy skies. Partly cloudy skies, becoming sunny.
Temperatures: 33 to 43 deg. F. 28 to 38 deg. F. 35 to 45 deg. F.
Wind direction: NW NW N
Wind speed: 40 to 55 mph with gusts to 75 mph. 35 to 45 mph with gusts to 65 mph. 35 to 45 mph with gusts to 70 mph.
Expected snowfall: 0 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.

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