THIS AVALANCHE ADVISORY EXPIRED ON December 1, 2016 @ 6:41 am
Avalanche Advisory published on November 30, 2016 @ 6:41 am
Issued by Brandon Schwartz - Tahoe National Forest

Avalanche danger is LOW for all elevations and aspects. A low likelihood, high consequence persistent slab avalanche problem remains on N aspects both above and below treeline in specific areas. Very isolated wind slabs may linger on any aspect in near and above treeline terrain.

Normal caution is advised for managing the wind slab problem. Extra caution and conservative terrain choices are advised for managing the persistent slab problem.

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: Persistent Slab
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The persistent slab problem remains a low likelihood, high consequence situation. The weak layer is faceted old snow buried 2 to 3 ft below the surface on N aspects along the northern portion of the Sierra Crest above 8,300', in the Mt. Rose area above 9,300', and in very isolated areas in the southern portion of the forecast area above 9,000'. Triggering has proven difficult, but day to day snowpit data continues to point out the potential for a fairly large avalanche occurrence.

When dealing with persistent slabs most informal observations do not give reliable information and existing tracks do not indicate stability. In areas where this avalanche problem is likely to exist, consider what information is truly known vs unknown before committing to travel in N aspect avalanche terrain. The simple strategy is to avoid N aspects steeper than 30 degrees in known suspect areas. Otherwise, a fair bit of investigative work will be required to determine if the problematic snowpack structure exists on the slope of interest.

Avalanche Problem 2: Normal Caution
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Triggering an isolated wind slab avalanche is very unlikely today, but not all together impossible. Very, very isolated instability could linger in near treeline or above treeline terrain on any aspect due to recent shifting winds and blowing snow. Normal caution is advised for travel on recently wind loaded slopes.

advisory discussion

The deepest and most usable snowpack within the forecast area exists along the northern portion of the Sierra Crest. Along the Sierra Crest south of Tahoe City, snowpack depths decrease, even at the highest elevations. Recent storms have added to the snowpack in all areas but many rocks and shallowly buried obstacles still exist. The Mount Rose area in the NE portion of the forecast area has decent snowcover, but impact with rocks remains likely at the lower elevations in this area as well.

All of the recent avalanche and snowpack observations submitted by local users have been greatly appreciated and have contributed towards producing the best possible avalanche advisories. Please continue to submit observations through the "submit observations" buttons found throughout this website.

recent observations

Observations made and received yesterday from the Upper Meiss Drainage (Carson Pass area), Mt. Judah (Donner Summit area), and Lincoln Ridge (Yuba Pass area) revealed evidence of significant previous wind transport. Widespread areas of wind scouring were noted on all aspects, with pockets of high density wind deposited snow. Recently formed wind slabs existed but revealed no signs of instability. On Castle Peak (Donner Summit area), snowpit data collected on a N aspect at ~8,650' continued to point out the ongoing persistent slab problem.

Weather and CURRENT CONDITIONS
weather summary

A weak storm system is expected to pass by to the NE of the forecast area this afternoon and tomorrow. Light snow showers and colder air are all that is expected locally. Maximum daytime air temperatures above 7,000' are forecast in the low to mid 30s for today and in the 20s for tomorrow. Ridgetop winds shifted back to the SW early this morning and are moderate in speed. Winds are forecast to shift back to the NE tomorrow and resume moderate speed. Short lived high pressure is expected to build Thursday night into Friday.

Weather observations from along the Sierra Crest between 8200 ft. and 8800 ft.
0600 temperature: 18 to 29 deg. F.
Max. temperature in the last 24 hours: 30 to 38 deg. F.
Average wind direction during the last 24 hours: NE shifting to SW
Average wind speed during the last 24 hours: 18 mph
Maximum wind gust in the last 24 hours: 41 mph
New snowfall in the last 24 hours: 0 inches
Total snow depth: 13 to 23 inches
Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 7000 ft. to 8000 ft.
Wednesday Wednesday Night Thursday
Weather: Partly cloudy skies, becoming mostly cloudy. Slight chance of snow showers in the afternoon. Mostly cloudy skies. Slight chance of snow showers in the evening. Chance of snow showers after midnight. Partly cloudy skies, becoming mostly cloudy. Chance of snow showers in the morning. A slight chance of snow showers in the afternoon.
Temperatures: 32 to 37 deg. F. 15 to 20 deg. F. 25 to 30 deg. F.
Wind Direction: W NW NE
Wind Speed: Light winds, increasing to 10 to 15 mph with gusts to 25 mph in the afternoon. Light winds Light winds, increasing to 10 to 15 mph with gusts to 30 mph in the afternoon.
Expected snowfall: 0 to trace in. Up to 1 in. Up to 1 in.
For 8000 ft. to 9000 ft.
Wednesday Wednesday Night Thursday
Weather: Partly cloudy skies, becoming mostly cloudy. Slight chance of snow showers in the afternoon. Mostly cloudy skies. Slight chance of snow showers in the evening. Chance of snow showers after midnight. Partly cloudy skies, becoming mostly cloudy. Chance of snow showers in the morning. A slight chance of snow showers in the afternoon.
Temperatures: 28 to 32 deg. F. 14 to 19 deg. F. 20 to 25 deg. F.
Wind Direction: W NW NE
Wind Speed: 15 to 20 mph with gusts to 40 mph. 10 to 15 mph with gusts to 40 mph. 10 to 20 mph with gusts to 35 mph, increasing to 15 to 25 mph with gusts to 45 mph in the afternoon.
Expected snowfall: 0 to trace in. Up to 1 in. Up to 1 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.

For a recorded version of the Avalanche Advisory call (530) 587-3558 x258