THIS AVALANCHE ADVISORY EXPIRED ON December 2, 2015 @ 6:55 am
Avalanche Advisory published on December 1, 2015 @ 6:55 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. It is still early season and the snowpack is relatively shallow. Numerous barely covered rocks, stumps, logs, and other hazards exist.

1. Low

?

Above Treeline
Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.

1. Low

?

Near Treeline
Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.

1. Low

?

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

The current snowpack stability is good in many areas. However in specific areas, day after day field observations indicate potential isolated pockets of instability and the potential for developing avalanche problems in the short term. Faceted weak layers reactive to snowpit tests are continually found near treeline and below treeline on many but not all NW-N-NE aspects. These weak layers are usually found at the bottom of the snowpack and occasionally at mid height within the snowpack. In both cases there is an overlying slab. In areas where either of these snowpack structures exist, any signs of instability including collapse, whumpfing, cracking, or unstable snowpit test results are cause for conservative decision making. Small difficult to trigger (ie unlikely) avalanches are both an ongoing issue and a potential more significant future avalanche problem requiring both thought and a specific management plan while moving in and below avalanche terrain. Communicate with your travel partner(s), examine the snowpack, make a specific travel plan, stick to your plan.

recent observations

Despite warming air temperatures at the mid and upper elevations, little change has occurred in the overall snowpack structure from one day to the next. 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 Rubicon Peak (West Shore Tahoe area), snowpit tests revealed sudden collapse and propagation results on basal facets near treeline and below treeline on both NE and NW aspects between 8,500' and 8,900'. This is very similar to what was observed the day before on Castle Peak (Donner Summit area) and in several other locations around the forecast area over the past week (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 certain 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. On the E-SE-S-SW-W aspects, a very shallow well anchored snowpack exists with the most recent new snow transitioning to melt-freeze layering. Numerous barely covered rocks, stumps, logs, etc present a significant hazard to over snow travel on all aspects.

Weather and CURRENT CONDITIONS
weather summary

The warming trend at the mid and upper elevations continues under inversion conditions. That combined with cloud cover last night has led to the warmest upper elevation 6am air temperatures in the last week. Maximum daytime air temperatures above 7,000' are forecast to reach the low to upper 30s today and the mid 30s to low 40s tomorrow. Some light precipitation is expected to pass just to the north of the forecast area late tonight and tomorrow with the local effects of increasing cloud cover and SW ridgetop winds increasing to moderate in speed. The next storm system is forecast to reach the region on Thursday with gale force winds and snowfall expected.

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: 30 to 36 deg. F.
Average wind direction during the last 24 hours: SW
Average wind speed during the last 24 hours: 14 mph
Maximum wind gust in the last 24 hours: 37 mph
New snowfall in the last 24 hours: 0 inches
Total snow depth: 15 to 22 inches
Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 7000 ft. to 8000 ft.
Tuesday Tuesday Night Wednesday
Weather: Partly coudy skies. Mostly cloudy skies. Mostly cloudy skies.
Temperatures: 32 to 39 deg. F. 21 to 27 deg. F. 37 to 44 deg. F.
Wind Direction: SW S SW
Wind Speed: Light winds Light winds becoming around 10 mph after midnight. 10 to 15 mph. Gusts up to 25 mph in the afternoon.
Expected snowfall: 0 in. 0 in. 0 in.
For 8000 ft. to 9000 ft.
Tuesday Tuesday Night Wednesday
Weather: Partly coudy skies. Mostly cloudy skies. Mostly cloudy skies.
Temperatures: 30 to 37 deg. F. 24 to 29 deg. F. 36 to 43 deg. F.
Wind Direction: SW SW SW
Wind Speed: Light winds 10 to 15 mph 15 to 20 mph with gusts to 30 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.