THIS AVALANCHE FORECAST EXPIRED ON April 13, 2018 @ 6:50 am
Avalanche Forecast published on April 12, 2018 @ 6:50 am
Issued by Andy Anderson - Tahoe National Forest - Sierra Avalanche Center

MODERATE avalanche danger exists at all elevations due to wind slab problems and some possible storm slab avalanche problems. Human triggered slab avalanche activity will be possible today. If less clouds develop than forecasted today, wind slab and storm slab avalanches may be easier to trigger on sun-expsosed slopes and some loose wet instabilities could also form.

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: Wind Slab
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New snow and strong winds have created new wind slabs on wind-loaded NW-N-NE-E-SE aspects in near and above treeline terrain. Strong winds today should allow wind-loading to continue in some areas. Human triggered wind slab avalanches will be possible today and some of these could entrain enough snow to bury or injure a person. If less clouds develop than forecasted today, strong april sunshine could make these wind slabs even easier to trigger especially on E and SE aspects.

Use clues blowing snow, cornices above a slope, drifted snow, ripples in the snow surface, and other wind created features to identify where wind slabs may exist. Avoid those areas in favor of more sheltered slopes where softer snow is also more likely to exist.

Avalanche Problem 2: Storm Slab
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Changing conditions during the storm may have created some weaknesses within the storm snow. Some storm slab avalanche problems may be possible in areas that recieved the most new snow last night. In most places any storm slabs that do exist should remain small, but some could pose more of a threat especially when paired with a terrain trap that could magnifiy the consequences of any size avalanche. Like the wind slabs mentioned above, strong april sunshine could make storm slabs easier to trigger on sun-exposed slopes where the most new snow exists if less clouds develop than forecasted today. Sun exposure may also tigger some loose wet instabilities if the forecasted cloud cover does not materialize.

Recent avalanche activity, shooting cracks, and feeling layer changes in the storm snow can all indicate that storm slab issues may be present. Stay alert and continually assess the snowpack and terrain around you for clues that can help avoid potential avalanche problems. Conditions can change quickly from cold soft snow to sunny warm unstable snow. 

recent observations
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* Observations on Chickadee Ridge yesterday showed limited melting and softening on the sun-exposed southerly aspects and firm frozen snow surfaces on the northerly aspects. Data and observations indicated that the existing snowpack should handle the new load well. 

Weather and CURRENT CONDITIONS
weather summary

A cold April storm hit the forecast area last night with strong southwest winds and 4 to 8 inches of new snow in the mountains. The snowfall tapered off early this morning and most of the clouds cleared out. The winds have started to shift to the west as well. The winds should remain strong through today. A weaker storm well north of the forecast area could push some cloud cover and isolated snow showers back over the region this afternoon. By tonight a high pressure ridge should begin to build over the region. Expect a clear cold night tonight with strong northwest and northeast winds. Temperatures should warm up significantly tomorrow with daytime highs in the 40's above 7000 ft. and clear sunny skies. Winds should move to the northeast tomorrow but they should decrease in strength by the afternoon.

CONDITIONS ALONG THE SIERRA CREST BETWEEN 8200 FT. AND 9200 FT. IN THE LAST 24 HOURS
Weather Station Map
Weather Station Table
6am temperature: 14 to 19 deg. F.
Max. temperature: 40 to 44 deg. F.
Average ridgetop wind direction: Southwest
Average ridgetop wind speed: 50 mph
Maximum ridgetop wind gust: 100 mph
New snowfall: 4 to 8 inches
Total snow depth: 53 to 93 inches
Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 7000 ft. to 8000 ft.
Thursday Thursday Night Friday
Weather: Partly cloudy / mostly clear this morning with increasing clouds and isolated snow showers as the day progresses. Partly cloudy with isolated snow showers in the evening becoming clear overnight Sunny
Temperatures: 29 to 35 deg. F. 16 to 21 deg. F. 44 to 49 deg. F.
Mid Slope Winds: West West Variable
Wind Speed: 15 to 20 mph with gusts to 40 mph 10 to 15 mph with gusts to 35 mph in the evening becoming light overnight 10 to 15 mph with gusts to 40 mph in the morning decreasing to 5 to 10 mph with gusts to 25 mph in the afternoon
Expected snowfall: up to 1 0 0
For 8000 ft. to 9000 ft.
Thursday Thursday Night Friday
Weather: Partly cloudy / mostly clear this morning with increasing clouds and isolated snow showers as the day progresses. Partly cloudy with isolated snow showers in the evening becoming clear overnight Sunny
Temperatures: 24 to 30 deg. F. 13 to 18 deg. F. 39 to 45 deg. F.
Ridge Top Winds: West Northwest Northeast
Wind Speed: 20 to 30 mph with gusts to 60 mph decreasing to 40 mph in the afternoon 20 to 30 mph with gusts to 35 mph increasing to 60 mph after midnight 20 to 30 mph with gusts to 55 mph decreasing to 15 to 20 mph with gusts to 40 mph in the afternoon
Expected snowfall: up to 1 0 0
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