THIS AVALANCHE ADVISORY EXPIRED ON November 29, 2015 @ 6:45 am
Avalanche Advisory published on November 28, 2015 @ 6:45 am
Issued by Brandon Schwartz - Tahoe National Forest

LOW avalanche danger exists for all elevations and aspects. Small avalanches in isolated areas are quite possible given the current snowpack structure. Triggering is unlikely, but far from impossible. This fits the definition of LOW avalanche danger. It is a myth that LOW danger equals no danger. Exercise best practice backcountry travel techniques and manage terrain wisely.

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

Small avalanches in isolated areas remain an ongoing concern. Redistribution of snow on the ground has created small pockets of wind slab on all aspects near and above treeline. Any above treeline areas that look to have a nice swath of continuous snow cover are highly suspect for a wind slab problem. Some slabs are hard and may sound hollow. Consider consequences of a small avalanche in terms of secondary terrain hazards below such as rocks, trees, cliffs, and terrain traps.

Near treeline and below treeline NW-N-NE aspects with protection from NE winds are harboring pockets of isolated instability in the form of storm and/or wind slab on top of faceted snow. The firmer snow over softer snow structure is easily identified and the faceted weak layer has been observed both mid height in the snowpack and at ground level. Poke, prod, and investigate the snowpack. Human triggered collapse, whumpfing sounds, or unstable snowpit tests results are all reasons to back away to lower angle terrain.

 

recent observations

Significant spacial variability exists across the forecast area. In some locations no evidence of instability is observed. Within other sections of the forecast area, slopes of similar aspect and elevation are revealing isolated skier triggered collapse/whumpfing and associated unstable snowpit test results. Stay on your game and anticipate isolated packets of instability that could lead to small human triggered avalanches. Just because you or your buddy did not see evidence of instability yesterday does not mean that you will not find it today in a different location.

Recent observations from around the forecast area have pointed to concerns with mid height and basal facets near treeline and below treeline on NW-N-NE aspects. During the warm period prior to the last storm cycle, these layers were observed to round and gain strength. With plummeting snowpack temperatures post storm, these layers have returned to a faceting regime. The shallow snowpack is allowing for strong snow temperature gradients and these weak layers are now becoming weaker. These faceted weak layers have been observed both at ground level and at mid height within the snowpack. In either case there is a slab resting on top of these weak layers. The basal layer often has a fair bit of anchoring, the mid height layer tends not to have any anchoring. Again, expected avalanche size is small and triggering is unlikely, but isolated areas of instability are out there.

Weather and CURRENT CONDITIONS
weather summary

The trough of low pressure that brought the last storm system, cold air, and lingering snow showers will begin to shift to the east today. High pressure and inversion conditions will move into the region tomorrow. This will set the stage for a warming trend at the mid and upper elevations over the next few days. Expect maximum daytime air temperatures above 7,000' in the mid teens to mid 20s today and low 20s to low 30s tomorrow. Ridgetop winds are diminishing this morning. Light to moderate in speed winds are forecast for today, tonight, and tomorrow.

Weather observations from along the Sierra Crest between 8200 ft. and 8800 ft.
0600 temperature: 6 to 13 deg. F.
Max. temperature in the last 24 hours: 16 to 23 deg. F.
Average wind direction during the last 24 hours: NE
Average wind speed during the last 24 hours: 35 mph
Maximum wind gust in the last 24 hours: 55 mph
New snowfall in the last 24 hours: 0 to trace inches
Total snow depth: 16 to 24 inches
Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 7000 ft. to 8000 ft.
Saturday Saturday Night Sunday
Weather: Partly cloudy skies. Partly cloudy skies, becoming clear. Sunny skies.
Temperatures: 20 to 27 deg. F. 4 to 10 deg. F. 23 to 30 deg. F.
Wind Direction: E Variable Variable
Wind Speed: 10 to 15 mph Light winds Light winds
Expected snowfall: 0 in. 0 in. 0 in.
For 8000 ft. to 9000 ft.
Saturday Saturday Night Sunday
Weather: Partly cloudy skies. Partly cloudy skies, becoming clear. Sunny skies.
Temperatures: 16 to 23 deg. F. 4 to 10 deg. F. 20 to 27 deg. F.
Wind Direction: SE Variable SE
Wind Speed: 15 to 20 mph with gusts to 30 mph. Light winds Light winds increasing to 10 to 15 mph in the afternoon.
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.