Avalanche Advisory published on January 22, 2017 @ 6:59 am
This Avalanche Advisory expires in 2 hours, 56 minutes
This advisory is valid for 24 hours
Issued by Andy Anderson - Tahoe National Forest
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HIGH avalanche danger exists at all elevations. Due to heavy snow, intense snowfall rates, and gale force winds human triggered wind slab avalanches and storm slab avalanches will be very likely today and natural avalanches will be likely. Some avalanches could be large, deep, and destructive. Travel in or near avalanche terrain or in the runout zones of avalanche paths is not recommended.

How to read the advisory


  • Very dangerous avalanche conditions. Travel in avalanche terrain not recommended.

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HIGH avalanche danger exists at all elevations. Due to heavy snow, intense snowfall rates, and gale force winds human triggered wind slab avalanches and storm slab avalanches will be very likely today and natural avalanches will be likely. Some avalanches could be large, deep, and destructive. Travel in or near avalanche terrain or in the runout zones of avalanche paths is not recommended.

  • Very dangerous avalanche conditions. Travel in avalanche terrain not recommended.
Avalanche Problem 1: Wind Slab
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Large, deep, and widespread human triggered wind slab avalanches are very likely today and natural wind slab avalanches are likely. Heavy snowfall and gale force S and SW winds have and will continue to form larger, deeper, and more widespread wind slabs on wind-loaded W-NW-N-NE-E-SE aspects. The largest and most sensitive wind slabs should exist in near and above treeline terrain and could have crowns deeper than 4 to 6 ft, but some wind slabs may also exist on wind loaded slopes in below treeline terrain. 

Blowing snow, cornices, wind drifted snow, and other wind created features and textures can help identify where wind slabs may exist. Avoid those areas and the runout zones of potential wind slab avalanches

Avalanche Problem 2: Storm Slab
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Heavy snowfall with rates of 2+ inches per hour at times and changing conditions during the storm that create slabs and weak layers within the storm snow mean that human triggered storm slab avalanches will become very likely today and natural storm slabs will become likely. As more snow impacts the region in the next 18 hrs these storm slabs could become larger and more widespread. Any steep slopes with new snow on them hold the potential for storm slab avalanches

Clues like cracking, collapsing, and whumphing can help identify where storm slabs may exist as can digging into the snowpack with your hands or probing with a pole to look for layers in the storm snow. Use these clues to avoid steep terrain where storm slabs may exist. Storm slabs can exist on tree covered slopes in the openings between trees and may connect across some of these open spaces. 

recent observations

Yesterday observations on Tamarack Peak found ski kicks could easily trigger wind slab avalanches on exposed N-NE aspects with crowns of up to 2 ft. Shooting cracks caused by a skiers weight also occurred on wind loaded slopes. In more sheltered near and below treeline terrain on Tamarack Peak, Jakes Peak, and on Luther Pass, observations showed weaknesses within the recent storm snow, but fractures did not readily propagate along these weaknesses in many areas. Some skier triggered small cracking occurred on Tamarack and on Luther Pass in some sheltered areas. On Luther Pass, a ski cut on one test slope did produce a small storm slab failure. On Jakes Peak and in other areas on Tamarack and Luther Pass, ski cuts on test slopes only produced loose dry sluffs. Observations from lower elevation slopes (below 6400 ft) on Schallenberger Ridge did not find signs of slab formation or instability.

CURRENT CONDITIONS Weather observations from along the Sierra Crest between 8200 ft. and 8800 ft.
0600 temperature: 25 to 29 deg. F.
Max. temperature in the last 24 hours: 25 to 29 deg. F.
Average wind direction during the last 24 hours: South and southwest
Average wind speed during the last 24 hours: 35 to 50 mph
Maximum wind gust in the last 24 hours: 139 mph
New snowfall in the last 24 hours: 4 to 12 inches
Total snow depth: 107 to 137 inches
weather

A winter storm warning is in effect until Monday morning. Another strong winter storm has arrived over the forecast area bringing gale force winds and heavy snow to the region. Snowfall and wind speeds have already started to increase and intensify and should continue through midnight tonight. This storm has pulled some warmer air into the region with the first wave of snowfall and temperatures should be slightly warmer today than yesterday. Despite this warming, snow levels should remain below 4500 to 5000 ft. The forecast calls for 12 to 18 inches of snow above 7000 ft. and 13 to 20 inches above 8000 ft. during the day before a second wave of intense snowfall arrives this afternoon and evening. This second wave should accompany a cold front and temperatures should fall into the teens overnight. Another 12 to 20 inches of colder snow should accumulate overnight with most of that arriving before midnight. After midnight the snowfall and winds should start to decease and continue decreasing into Monday as the storm exits the region. Lingering snow showers could still produce 2 to 4 inches of snow on Monday and temperatures should remain about 5 degrees colder than today. For more details on the winter storm check in with the Reno NWS

Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 7000 ft. to 8000 ft.
  Sunday Sunday Night Monday
Weather: Snow Snow Cloudy with snow showers in the morning, then scattered snow showers in the afternoon
Temperatures: 25 to 30 deg. F. 16 to 21 deg. F. 21 to 26 deg. F.
Wind direction: Southwest Southwest Southwest
Wind speed: 20 to 35 mph with gusts to 75 mph 15 to 25 mph with gusts to 55 mph decreasing to 45 mph after midnight 10 to 15 mph with gusts to 30 mph
Expected snowfall: 12 to 18 in. 12 to 18 in. 2 to 4 in.
For 8000 ft. to 9000 ft.
  Sunday Sunday Night Monday
Weather: Snow Snow Cloudy with snow showers in the morning, then scattered snow showers in the afternoon
Temperatures: 22 to 27 deg. F. 14 to 19 deg. F. 17 to 23 deg. F.
Wind direction: Southwest Southwest Southwest
Wind speed: 45 to 60 mph with gusts to 140 mph decreasing to 35 to 55 mph with gusts to 130 mph in the afternoon 30 to 45 mph with gusts to 110 mph decreasing to 25 to 35 mph with gusts to 90 mph after midnight 15 to 25 mph with gusts to 55 mph decreasing to 45 mph in the afternoon
Expected snowfall: 13 to 20 in. 13 to 20 in. 2 to 4 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

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