THIS AVALANCHE FORECAST EXPIRED ON March 15, 2018 @ 6:55 am
Avalanche Forecast published on March 14, 2018 @ 6:55 am
Issued by Steve Reynaud - Tahoe National Forest

Considerable avalanche danger will continue due to wind slab and storm slab avalanche problems.  Wind slabs will be likely in near treeline and above treeline terrain.  Storm slabs will be likely in near treeline and below treeline terrain.  Careful snowpack evaluation, cautious route finding, and conservative decision making are essential today.

3. Considerable

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Above Treeline
Dangerous avalanche conditions. Careful snowpack evaluation, cautious route-finding and conservative decision-making essential.

3. Considerable

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Near Treeline
Dangerous avalanche conditions. Careful snowpack evaluation, cautious route-finding and conservative decision-making essential.

3. Considerable

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Below Treeline
Dangerous avalanche conditions. Careful snowpack evaluation, cautious route-finding and conservative decision-making essential.
    Dangerous avalanche conditions. Careful snowpack evaluation, cautious route-finding and conservative decision-making essential.
Avalanche Problem 1: Wind Slab
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Winds slabs will be likely in near and above treeline terrain on NW-N-NE-E-SE aspects.  Strong to gale force SW winds will continue through today with additional snowfall.  

Look for signs of recent wind slab avalanches, blowing snow, cornices, cornice formation, and wind pillows.  Avoid steep wind loaded terrain and run out zones below corniced slopes.

Avalanche Problem 2: Storm Slab
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Storm slabs will be likely on all aspects in near treeline and below treeline terrain.  Another 1' of additional snow is expected throughout today in the higher elevations with the potential for high snowfall intensity.  In areas where slab cohesion does not exist, loose dry avalanches (sluffing) could present travel concerns for backcountry users in steep wind protected terrain. 

Look for signs of cracking or cohesion of the new storm snow.  Hand pits could provide a good tool for looking at the bonding of the new storm snow.  Avoid slopes with signs of unstable snow.

Forecast discussion

Continued observations on the recent deep slab avalanche problem have shown signs of overall increasing stability.  The previous faceted weak layer of concern is now buried 2.5 to 6 feet deep in the snowpack on NW-N-NE-ENE aspects and has been found at all elevations.  This layer has gone through varying degrees of rounding at many locations and has gained strength.  In other isolated locations, striated faceted grains are still visible under magnification.  This previously faceted layer does remain significantly less dense than the strong slab above it.  Snowpack tests mostly indicate that weak layer failure and propagation is unlikely, although there have been some outliers.  These outliers have been located in isolated areas of Luther Pass, Echo Summit, and Carson Pass.  At this time, data does not exist to warrant an avalanche problem.   

 

recent observations
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* High elevation rain was reported from Incline Lake Peak (Mt. Rose area).  Thin rain crusts were found up to 9200' yesterday morning.  Snow began at 11:30am with snow levels around 8000'.

* Large roller ball activity was observed on Andesite Peak (Donner Summit area) with moderate rainfall on Donner Summit throughout the day.

Weather and CURRENT CONDITIONS
weather summary

9 to 17'' of new snow fell overnight at the higher elevations along the Sierra Crest and the Mt. Rose area.  Light to moderate snow is expected to continue through today and tonight with slow levels continuing to lower throughout the morning.  Another 1' of snow along the Sierra Crest with 3 to 6'' at Lake level are expected by Thursday morning.  Convective snow showers could be possible in the Tahoe Basin resulting in some areas receiving much more snow than others at higher snowfall rates.  

The next storm is set for Thursday night through Saturday morning.  Some changes have been made to this storm with a slight decrease in moisture as this storm heads south of our area.  Snow showers will linger throughout the weekend.  After a brief break, another storm is possible for Tuesday next week.   

CONDITIONS ALONG THE SIERRA CREST BETWEEN 8200 FT. AND 9200 FT. IN THE LAST 24 HOURS
Weather Station Map
Weather Station Table
6am temperature: 22 to 26 deg. F.
Max. temperature: 38 deg. F.
Average ridgetop wind direction: SW
Average ridgetop wind speed: 30 to 50 mph
Maximum ridgetop wind gust: 90 mph
New snowfall: 9 to 11 inches
Total snow depth: 52 to 85 inches
Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 7000 ft. to 8000 ft.
Wednesday Wednesday Night Thursday
Weather: Cloudy. Snow showers. Cloudy. Chance of snow showers. Cloudy. Chance of snow in the morning, then snow likely in the afternoon.
Temperatures: 29 to 34 deg. F. 16 to 21 deg. F. 27 to 32 deg. F.
Mid Slope Winds: SW W SW
Wind Speed: 10 to 15mph with gusts up to 30mph in the afternoon. 10 to 15mph with gusts to 30mph. 15 to 25mph. Gusts to 35mph increasing to 45mph in the afternoon.
Expected snowfall: 3 to 7 1 to 3 Up to 2
For 8000 ft. to 9000 ft.
Wednesday Wednesday Night Thursday
Weather: Cloudy. Snow showers likely in the morning, then snow showers in the afternoon. Cloudy. Snow showers in the evening, then chance of snow showers after midnight. Cloudy. Chance of snow showers in the morning then snow likely in the afternoon.
Temperatures: 24 to 30 deg. F. 12 to 18 deg. F. 22 to 28 deg. F.
Ridge Top Winds: SW W SW
Wind Speed: 20 to 30mph. Gusts to 55mph decreasing to 50mph in the afternoon. 15 to 25mph with gusts to 45mph. 20 to 30mph. Gusts to 45mph increasing to 65mph in the afternoon.
Expected snowfall: 4 to 8 1 to 3 Up to 2
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