THIS AVALANCHE ADVISORY EXPIRED ON December 1, 2015 @ 6:45 am
Avalanche Advisory published on November 30, 2015 @ 6:45 am
Issued by Brandon Schwartz - Tahoe National Forest

LOW avalanche danger continues for all elevations and aspects. The potential exists for the unlikely triggering of small avalanches in isolated areas. Continue to use accepted best practice travel techniques while traveling in or below avalanche terrain. Keep exposure limited to one person at a time and avoid grouping in avalanche run out zones.

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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  • Aspect/Elevation ?
  • Likelihood ?
    Certain
    Very Likely
    Likely
    Possible
    Unlikely
  • Size ?
    Historic
    Very Large
    Large
    Small

Inherently less stable early season snowpack conditions continue across the forecast area. In many areas current snow stability is good. In other areas that is not the case. Isolated pockets of instability are continually found near treeline and below treeline on NW-N-NE aspects. In some but not all of these areas, faceted weak layers are found below a slab either at mid height or at the bottom of the snowpack. In areas where this snowpack structure exists, any signs of instability including collapse, whumpfing, or unstable snowpit test results are cause for conservative decision making. Take time to investigate the snowpack and do not take stability for granted due to regional LOW danger. Difficult to trigger (ie unlikely) avalanches are an ongoing issue requiring some thought and management while moving in and below avalanche terrain.

recent observations

Recent field observations continue to identify difficult to trigger problematic faceted weak layers in some but not all near treeline and below treeline areas on NW-N-NE aspects. Yesterday on Castle Peak (Donner Summit area), snowpit tests revealed sudden collapse and propagation results on basal facets near treeline on a NW aspect at 8,860'. Over the past week, problematic snowpit test results and at times skier triggered collapse and whumpfing were observed in other locations on N-NE aspects between 7,700' and 9,500' in the Donner Summit, Mount Rose, Pole Creek, Independence Lake, and Carson Pass areas (more info below). In areas where these weak layers are absent, no obvious signs of instability or unstable snowpit test results have been observed. Strong temperature gradients within portions of the snowpack indicate that faceting will continue in the short term.

Above treeline and on the sun exposed E-SE-S-SW-W aspects conditions are very similar across the forecast area. Pockets of wind scouring and wind drifted snow exist above treeline. Evidence of instability above treeline has been minimal and limited to very minor human triggered cracking of wind pillows and wind slabs over the past few days. On the sun exposed and wind protected slopes, a very shallow well anchored snowpack exists with the most recent new snow covering either melt-freeze layering or ground level rocks and vegetation.

Weather and CURRENT CONDITIONS
weather summary

Weak high pressure over the region will keep inversion conditions ongoing with continued warming at the mid and upper elevations over the next couple of days. Maximum daytime air temperatures above 7,000' are forecast to reach the mid 20s to mid 30s today and low 30s to low 40s tomorrow. A weak weather system, mostly broken apart after encountering the high pressure ridge will move through the forecast area today and tonight. Increasing cloud cover will be the main impact with isolated snow showers possible today, most likely occurring this evening. No significant accumulation is expected. Ridgetop winds are increasing in speed this morning out of the SW with gusts 30 to 40 mph expected. Moisture ahead of the next significant storm system forecast to arrive Thursday will increase precipitation chances late tomorrow night and Wednesday.

Weather observations from along the Sierra Crest between 8200 ft. and 8800 ft.
0600 temperature: 13 to 27 deg. F.
Max. temperature in the last 24 hours: 24 to 36 deg. F.
Average wind direction during the last 24 hours: SW
Average wind speed during the last 24 hours: 10 mph
Maximum wind gust in the last 24 hours: 35 mph
New snowfall in the last 24 hours: 0 inches
Total snow depth: 17 to 24 inches
Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 7000 ft. to 8000 ft.
Monday Monday Night Tuesday
Weather: Partly cloudy skies, becoming mostly cloudy. Mostly cloudy skies, becoming partly cloudy. Slight chance of snow showers in the evening. Partly cloudy skies.
Temperatures: 30 to 35 deg. F. 18 to 23 deg. F. 38 to 42 deg. F.
Wind Direction: SW SW Variable
Wind Speed: 10 to 15 mph 10 to 15 mph with gusts to 25 mph in the evening, becoming light. Light winds
Expected snowfall: 0 in. 0 to trace in. 0 in.
For 8000 ft. to 9000 ft.
Monday Monday Night Tuesday
Weather: Partly cloudy skies, becoming mostly cloudy. Mostly cloudy skies, becoming partly cloudy. Slight chance of snow showers in the evening. Partly cloudy skies.
Temperatures: 26 to 33 deg. F. 15 to 20 deg. F. 30 to 37 deg. F.
Wind Direction: SW W to SW SE
Wind Speed: 15 to 20 mph with gusts to 30 mph. 20 to 25 mph with gusts to 40 mph, shifting and decreasing to 10 to 15 mph after midnight. 10 to 15 mph
Expected snowfall: 0 in. 0 to trace 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.