THIS AVALANCHE ADVISORY EXPIRED ON March 3, 2014 @ 7:00 am
Avalanche Advisory published on March 2, 2014 @ 7:00 am
Issued by Andy Anderson - Tahoe National Forest

Pockets of MODERATE danger still exist on wind loaded slopes 35 degrees and steeper on NW-N-NE-E-SE aspects in near and above treeline terrain. Human triggered wind slab avalanches remain possible in some areas on these slopes especially on unsupported slopes, slopes with steep rollovers, couliors, and in complex and/or extreme terrain. The largest wind slabs exist south of Hwy. 50 where more snow fell. Some small loose wet avalanche activity may also occur today if the sun breaks through the clouds or temperatures climb higher than forecasted.

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.

1. Low

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Below Treeline
Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.
    Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.
Avalanche Problem 1: Wind Slab
  • Type ?
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  • Likelihood ?
    Certain
    Very Likely
    Likely
    Possible
    Unlikely
  • Size ?
    Historic
    Very Large
    Large
    Small

Triggering the dense wind slabs that exist on wind loaded near and above treeline slopes is becoming more difficult, but human triggered wind slab avalanches still remain possible in some areas. Unsupported slopes, slopes with steep rollovers, couliors, and complex and/or extreme terrain will hold the most fragile and highest consequence wind slabs. Wind slabs that fail today should do so at or above the interface between Wednesday night's snow and Friday night's snow where a softer layer of storm snow still remains. However, it is not impossible that some them could step down the the old snow layers and crusts below Wednesday night's snow making them much deeper.

recent observations

Near Frog Lake on Carson Pass, ski cuts on several N-NE facing, wind loaded test slopes resulted in shooting cracks and or wind slab failures. Steep and/or unsupported slopes proved the easiest to trigger. Slopes with good compressive support were much more difficult to trigger. A small piece of cornice dropped onto a slightly larger slope caused a small wind slab avalanche in this area yesterday. Snowpit tests at the site of that avalanche indicated that the wind slabs remained unstable and easy to trigger. These wind slabs failed on a layer of softer snow at the base of the more dense wind slabs. Wind slabs in this area looked to range between 8 and 18 inches in depth. Across the pass on Red Lake Peak, snowpit data from another party indicated signs of lingering weakness within storm snow as well at the interface between the old and new snow on the N aspects above Crater Lake. This party opted to come down the more E and SE facing highway side of the peak. Farther north on Andesite Ridge, ski cuts on one previously undercut, wind loaded, NE facing test slope also triggered a small 6-8 inch wind slab failure and some minor shooting cracks. In non-wind affected terrain on Andesite Peak, observations and data did not reveal any signs of instability.

Weather and CURRENT CONDITIONS
weather summary

Cloud cover started to decrease some last evening leading to a brief period of partial clearing in some areas. During the night widespread cloud cover began to return to the region. Clouds should remain in place over the forecast area through tonight. Some snow showers may accompany this cloudiness today. The northern part of the forecast area will have the best chances for seeing these light and scattered snow showers. Southwest winds should increase some today with speeds reaching into the 40 mph range with gusts to 65 mph along the mountain ridges above 8000 ft. Daytime highs should climb into the mid to upper 30's above 7000 ft. today with another 3 to 4 degrees of warming expected tomorrow. This unsettled cloudy, warm, and windy weather will continue into tomorrow.

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: 29 to 36 deg. F.
Average wind direction during the last 24 hours: Southwest
Average wind speed during the last 24 hours: 20 mph
Maximum wind gust in the last 24 hours: 41 mph
New snowfall in the last 24 hours: A trace to 0 inches
Total snow depth: 46 to 60 inches
Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 7000 ft. to 8000 ft.
Sunday Sunday Night Monday
Weather: Mostly cloudy with isolated snow showers in the morning. Snow showers becoming more widespread in the afternoon Mostly cloudy with scattered snow showers. Mostly cloudy with a slight chance of snow showers.
Temperatures: 32 to 39 deg. F. 22 to 29 deg. F. 36 to 43 deg. F.
Wind Direction: Southwest Southwest Southwest
Wind Speed: 15 to 20 mph with gusts to 30 mph increasing to 25 to 30 mph with gusts to 45 mph 20 to 30 mph with gusts to 40 mph 15 to 25 mph with gusts to 40 mph
Expected snowfall: trace in. trace in. trace in.
For 8000 ft. to 9000 ft.
Sunday Sunday Night Monday
Weather: Mostly cloudy with isolated snow showers in the morning. Snow showers becoming more widespread in the afternoon Mostly cloudy with scattered snow showers. Mostly cloudy with a slight chance of snow showers.
Temperatures: 33 to 39 deg. F. 20 to 27 deg. F. 36 to 42 deg. F.
Wind Direction: Southwest Southwest Southwest
Wind Speed: 20 to 25 mph with gusts to 40 mph increasing to 40 to 45 mph with gusts to 65 mph in the afternoon 30 to 40 mph with gusts to 60 mph 30 to 40 mph with gusts to 60 mph
Expected snowfall: trace in. trace in. trace 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.