THIS AVALANCHE ADVISORY EXPIRED ON April 14, 2017 @ 7:00 am
Avalanche Advisory published on April 13, 2017 @ 7:00 am
Issued by Andy Anderson - Tahoe National Forest

MODERATE avalanche danger exists at all elevations today due to wind slabs on wind-loaded slopes and possible storm slabs in more sheltered terrain. Human-triggered avalanches are possible today. Evaluate the snowpack and terrain carefully to identify where avalanche problems may exist. Use this information to avoid areas with possible avalanche problems. If the storm ends earlier than forecasted and the sun comes out, rapid warming could accentuate these problems and also cause loose wet avalanche problems to 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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Strong southwest winds and last night's snow combined with the new snow expected to fall today means that wind slabs will exist on wind-loaded slopes. Human-triggered wind slab avalanches will be possible today. 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, but some wind slabs could exist on open slopes in below treeline terrain as well due to the strength of the winds. 

Clues like blowing snow, 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 for better and safer recreation.

Avalanche Problem 2: Storm Slab
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Changing snowfall rates, winds, and other changing storm conditions combined with warming temperatures and additional snow today means that human-triggered storm slab avalanches may be possible in some areas especially where upside-down storm snow layering exists. The size and likelihood of these storm slab avalanches will depend on how much new snow an area has. The places with the most new snow hold the best potential for problematic storm slabs. While the possible storm slabs should remain smaller than the wind slabs mentioned above, some of the largest storm slabs could involve enough snow to injure or bury a person.

Recent avalanche activity, shooting cracks, snowpits, and probing can all help identify where storm slabs or upside-down layering may exist. Use this information to avoid steep slopes where storm slabs may exist. 

recent observations

Yesterday observations on Mt. Tallac found wet rain-soaked snow up to about 8700 ft. on northerly aspects and a mix of crusts and wet loose snow on all other aspects up to 9000 ft. Above 8700 ft. on the northerly aspects, a thin rain crust existed over colder snow. Ski cuts triggered large pinwheels and some loose wet sluffs on the northerly aspects below 8700 ft. and small pinwheels on the other aspects. Strong winds buffeted the area and rain fell up to at least 9000 ft. throughout the day.  

Weather and CURRENT CONDITIONS
weather summary

1 to 1.7 inches of precipitation has fallen on the forecast area in the last 24 hours. During the day yesterday, most of this fell as rain. As colder air moved into the region last night, snow levels fell and the precipitation changed over to snow. North of Hwy. 50, 6 to 10 inches of new snow has fallen since about midnight, while only 2 to 6 inches has accumulated in areas south of Hwy 50. Last night's gale force southwest winds should decrease some today, but they will remain strong with average speeds consistently in the 30 to 50 mph range with gusts up to 85 mph. This system will continue to spread south and weaken today. The forecast calls for another 2 to 5 inches of snow across the forecast area today. By tonight snow showers should come to an end and the cloud cover should begin to disperse. Expect a mostly sunny day with warmer temperatures and light southwest winds for Friday. 

Weather observations from along the Sierra Crest between 8200 ft. and 8800 ft.
0600 temperature: 25 to 31 deg. F.
Max. temperature in the last 24 hours: 34 to 43 deg. F.
Average wind direction during the last 24 hours: Southwest
Average wind speed during the last 24 hours: 60 mph
Maximum wind gust in the last 24 hours: 114 mph
New snowfall in the last 24 hours: South of Hwy 50: 2 to 6 inches | North of Hwy 50: 6 to 10 inches
Total snow depth: 126 to 196 inches
Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 7000 ft. to 8000 ft.
Thursday Thursday Night Friday
Weather: Cloudy with snow showers Mostly cloudy with scattered snow showers in the evening. Snow showers becoming isolated after midnight. Sunny becoming partly cloudy
Temperatures: 32 to 37 deg. F. 12 to 20 deg. F. 38 to 44 deg. F.
Wind Direction: Southwest Southwest Variable
Wind Speed: 20 to 30 mph with gusts to 60 mph decreasing to gusts to 40 mph in the afternoon 15 to 25 mph with gusts to 40 mph Light with gusts to 25 mph in the morning
Expected snowfall: 2 to 5 in. up to 1 in. 0 in.
For 8000 ft. to 9000 ft.
Thursday Thursday Night Friday
Weather: Cloudy with snow showers Mostly cloudy with scattered snow showers in the evening. Snow showers becoming isolated after midnight. Sunny becoming partly cloudy
Temperatures: 28 to 34 deg. F. 9 to 17 deg. F. 33 to 41 deg. F.
Wind Direction: Southwest Southwest Southwest
Wind Speed: 30 to 50 mph with gusts to 85 mph decreasing to 20 to 35 mph with gusts to 75 mph in the afternoon 20 to 30 mph with gusts to 65 mph decreasing to gusts to 55 mph after midnight 15 to 20 mph with gusts to 45 mph
Expected snowfall: 2 to 5 in. up to 1 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