THIS AVALANCHE ADVISORY EXPIRED ON April 15, 2017 @ 6:55 am
Avalanche Advisory published on April 14, 2017 @ 6:55 am
Issued by Andy Anderson - Tahoe National Forest

Rapid warming caused by April sun and warm temperatures will cause the avalanche danger to rise to CONSIDERABLE today. Large human-triggered loose wet avalanches will be likely today if people venture onto slopes where wet snow exists. Natural loose wet avalanches will be possible. This warming will also weaken the lingering wind slabs making human-triggered wind slab avalanches possible. Avoid slopes where signs of warming or wet snow exist and slopes where wind slabs remain especially if they receive sunshine.   

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: Loose Wet
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Strong April sunshine and much warmer daytime temperatures will cause rapid warming to occur in the new snow today. This rapid warming will weaken the new snow and human-triggered loose wet avalanche activity will become likely on any slopes that receive sunshine today. Some natural loose wet activity will be possible as well. These loose wet avalanches could entrain all of the new snow and could involve enough snow to pose problems for backcountry travelers. While loose wet avalanches should comprise most of the wet snow instabilities, some isolated wet slab avalanches are not impossible on the most sun-exposed slopes where the most new snow exists. 

Avoid slopes where signs of rapid warming like sticky wet surface snow, roller balls, pinwheels, or other signs of wet snow exist. Once the sun hits the slopes today, the snow will quickly become unstable and less fun to recreate on. Seek out shaded sheltered slopes where the snow remains cold and non-wind-affected for better and safer recreation. 

Avalanche Problem 2: Wind Slab
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Human-triggered wind slabs will remain possible on wind-loaded slopes where wind slabs formed during the storm. Today's rapid warming caused by a combination of sunshine and warming temperatures could also weaken the bonds holding these wind slabs to the slopes and make them more fragile and easier to trigger as the day warms up. Wind slabs could exist on wind-loaded N-NE-E aspects as well as on cross-loaded NW and SE aspects. Any wind slab avalanches that occur today could involve enough snow to bury or injure a person. The largest and most fragile wind slabs will exist in near and above treeline terrain in areas where the most new snow has accumulated on slopes that receive sunshine.

Clues like cornices above slopes, drifted snow, ripples in the snow surface, and other wind created textures can help identify where fragile wind slabs may exist. Use this information to avoid the wind slabs and to find sheltered non-wind-affected snow to travel on.

recent observations

Observations yesterday on Carson Pass, Echo Peak, Shirley Canyon, Silver Peak, and Incline Lake Peak all found 8 to 12 inches of new snow resting on top of wet rain crusts with wet snow beneath them. Some skier triggered loose wet avalanche activity was reported on lower elevation slopes in some areas. At the upper elevations, active wind-loading was widespread, but signs of wind slab instability were limited. Observers did report some small skier triggered loose dry sluffs. Skiers on Incline Lake Peak also triggered a small slab avalanche on a steep E facing slope. This slab was only 3 to 4 inches deep but did propagate across a slope.

Weather and CURRENT CONDITIONS
weather summary

Another 6 to 11 inches of new snow accumulated across the forecast area yesterday and into last evening. The snow showers and winds tapered off overnight and cloud cover started to clear as a small high-pressure ridge started to build over the area. The forecast calls for drier weather with mostly sunny skies today and tomorrow. Winds should remain light to moderate and temperatures will start to warm back up. Expect daytime highs in the upper 30's and low 40's today above 7000 ft. By tomorrow they should climb into the upper 40's and low 50's above 7000 ft. 

Weather observations from along the Sierra Crest between 8200 ft. and 8800 ft.
0600 temperature: 9 to 18 deg. F.
Max. temperature in the last 24 hours: 24 to 33 deg. F.
Average wind direction during the last 24 hours: Southwest
Average wind speed during the last 24 hours: Until midnight last night: 40 to 50 mph | Since midnight: 25 to 30 mph
Maximum wind gust in the last 24 hours: 100 mph
New snowfall in the last 24 hours: 6 to 11 inches
Total snow depth: 134 to 205 inches
Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 7000 ft. to 8000 ft.
Friday Friday Night Saturday
Weather: Mostly sunny with few clouds Mostly clear with few clouds Partly cloudy
Temperatures: 37 to 43 deg. F. 20 to 25 deg. F. 45 to 51 deg. F.
Wind Direction: Southwest Variable Southwest
Wind Speed: Around 10 mph with gusts to 25 mph in the morning Light Around 10 mph with gusts to 25 mph in the afternoon
Expected snowfall: 0 in. 0 in. 0 in.
For 8000 ft. to 9000 ft.
Friday Friday Night Saturday
Weather: Mostly sunny with few clouds Mostly clear with few clouds Partly cloudy
Temperatures: 32 to 40 deg. F. 18 to 23 deg. F. 41 to 47 deg. F.
Wind Direction: Southwest Southwest South
Wind Speed: 10 to 20 mph with gusts to 30 mph in the morning 10 to 15 mph 15 to 20 mph with gusts to 30 mph increasing to gusts to 45 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