THIS AVALANCHE ADVISORY EXPIRED ON January 31, 2018 @ 7:00 am
Avalanche Advisory published on January 30, 2018 @ 7:00 am
Issued by Andy Anderson - Tahoe National Forest

As the day warms up, the avalanche danger will increase to MODERATE due to the potential for loose wet avalanches.  A few isolated persistent slabs may also linger on some near and below treeline slopes, especially in the Carson Pass and Ebbetts Pass areas. 

2. Moderate

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Above Treeline
Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.

2. Moderate

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Near Treeline
Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.

2. Moderate

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Below Treeline
Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.
    Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.
Avalanche Problem 1: Loose Wet
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Partly cloudy skies with some sun and warmer temperatures should allow loose wet instabilities including roller balls, pinwheels, and point release avalanches to become possible on steep sun-exposed slopes again today. The stronger winds may help dimish the chances of larger loose wet instabilities. Most of these loose wet instabilities should not entrain enough snow to bury a person, but they could knock a person over or push a person into terrain where collisions or a fall would have serious consequences.

Avalanche Problem 2: Persistent Slab
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Persistent slabs are unlikely across most of the forecast area; however, isolated persistent slab avalanches may remain possible in the Carson Pass and Ebbetts Pass areas. If a persistent slab avalanche does occur, the failure layer would likely be loose weak snow near a crust 8 to 18 inches below the surface (near crust facets). Persistent slabs could involve enough snow to bury or injure a person (size D2 with some potential for an isolated D3).  Observations including snowpit tests and some snowmobile triggered shooting cracks over the last few days continue to indicate that this layer remains weak on some near and below treeline NW-N-NE facing slopes in the Carson Pass and Ebbetts Pass areas. Significant uncertainty still remains as to how widespread this problem may be.

Look for and avoid avalanche terrain in any areas where snow surface cracking, snowpack collapse/whumpfing, and/or unstable snowpit test results are occurring.

recent observations

* Snowpit tests targetting the near crust facet layer yielded unstable results on Elephants Hump (Carson Pass area) yesterday. This data is consistent with other signs of instability concerning this layer in the Carson Pass area and Ebbetts Pass area over the last few days. Snowpit data from Ophir Peak (Mt. Rose backcountry) revealed the presence of this layer, but did not show signs of current instability. 

* Observations from National Geographic Bowl (Granite Chief Wilderness) and Castle Peak (Donner Summit) both showed a well-bonded snowpack.

* Wet, sticky snow existed on all aspects below 9000 ft. on Elephants Hump, below 8500 ft. on Ophir Peak, and on the lower elevations of Granite Chief and Castle Peak. Roller balls and pinwheels occurred on N-NE-E aspects on Elephants Hump, on N-NE aspects of Ophir Peak, and all aspects on the lower elevations of Granite Chief.

* Observers reported large cornices and wind-loaded slopes on Castle Peak and Granite Chief but did not find lingering signs of instability concerning the wind slabs. They avoided testing the large cornices.  

 

Weather and CURRENT CONDITIONS
weather summary

Southwest winds started to increase overnight and should remain strong through this evening due to a system passing by to the north of the area. These winds should also bring even warmer air to the region allowing daytime highs to climb into the mid 50's above 7000 ft. The inversion conditions should also lift sooner than previous mornings. The forecast also calls for a mix of sun and some lingering thin high clouds through tomorrow.

Weather observations from along the Sierra Crest between 8200 ft. and 8800 ft.
0600 temperature: 37 to 45 deg. F.
Max. temperature in the last 24 hours: 49 to 51 deg. F.
Average wind direction during the last 24 hours: Southwest
Average wind speed during the last 24 hours: 10 to 20 mph
Maximum wind gust in the last 24 hours: 50 mph
New snowfall in the last 24 hours: 0 inches
Total snow depth: 29 to 54 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 cloudy to mostly sunny Partly cloudy to mostly clear Partly cloudy to mostly sunny
Temperatures: 50 to 55 deg. F. 27 to 32 deg. F. 49 to 54 deg. F.
Wind Direction: Southwest Southwest West
Wind Speed: 10 to 20 mph with gusts to 40 mph 10 to 20 mph with gusts to 40 mph decreasing to 30 mph after midnight 10 to 15 mph with gusts to 30 mph becoming light in the afternoon
Expected snowfall: 0 in. 0 in. 0 in.
For 8000 ft. to 9000 ft.
Tuesday Tuesday Night Wednesday
Weather: Partly cloudy to mostly sunny Partly cloudy to mostly clear Partly cloudy to mostly sunny
Temperatures: 45 to 51 deg. F. 27 to 32 deg. F. 45 to 51 deg. F.
Wind Direction: Southwest West West
Wind Speed: 20 to 30 mph with gusts to 60 mph 20 to 30 mph with gusts to 60 mph decreasing to 45 mph after midnight 20 to 30 mph with gusts to 50 mph decreasing to 15 to 20 mph with gusts to 40 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.

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