THIS AVALANCHE FORECAST EXPIRED ON March 11, 2016 @ 6:59 am
Avalanche Forecast published on March 10, 2016 @ 6:59 am
Issued by Andy Anderson - Tahoe National Forest - Sierra Avalanche Center

MODERATE avalanche danger exists on slopes steeper than 35 degrees on all aspects due to the possibility of loose wet avalanches in near and below treeline terrain and wind slabs in near and above treeline terrain above 8500 ft. Some human triggered avalanches will be possible today. Evaluate snow and terrain carefully, and identify areas where avalanche problems might exist.

2. Moderate

?

Above Treeline
Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.

2. Moderate

?

Near Treeline
Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.

2. Moderate

?

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: Loose Wet
  • Type ?
  • Aspect/Elevation ?
  • Likelihood ?
    Certain
    Very Likely
    Likely
    Possible
    Unlikely
  • Size ?
    Historic
    Very Large
    Large
    Small

Warm overnight temperatures and lingering cloud cover should mean that a weak refreeze occurred last night if a refreeze occurred at all. Continued warm temperatures and some rain below 8000 ft. will cause wet snow to form on some slopes again today. This wet snow will allow loose wet snow instabilities like roller balls, pinwheels, and some point releases to become possible again today. These wet snow instabilities should remain relatively small and less widespread than yesterday due to the gale force winds expected today, but some of them could still entrain enough snow to cause problems for backcountry travelers. Near and below treeline sun exposed E-SE-S-SW aspects and slopes below 8000 ft. that receive rain this afternoon represent the best places to find loose wet snow issues today. 

Avoid slopes that are steeper than 35 degrees or have terrain above that is 35 degrees as warming occurs today.  Active roller balls and pinwheels indicate that the snow is loosing strength, and it's time to change aspects or leave steeper terrain.

Avalanche Problem 2: Wind Slab
  • Type ?
  • Aspect/Elevation ?
  • Likelihood ?
    Certain
    Very Likely
    Likely
    Possible
    Unlikely
  • Size ?
    Historic
    Very Large
    Large
    Small

Gale force southwest winds will continue to transport any available snow from the windward aspects to the leeward NW-N-NE-E-SE aspects. Due to the melt-freeze cycle that happened yesterday less snow should remain available for transport and most wind slabs that do form today should remain relatively small and not extend very far away from ridgelines. Some larger more problematic wind slabs could form on leeward near and above treeline slopes above 8500 ft. where colder more easily transported snow still exists on some of the windward aspects. 

Identify and avoid steep wind loaded slopes.  Look for areas of blowing snow, cornice formation, wind scouring, and wind pillows to help determine where wind slabs exist.

recent observations
Submit Observations

Observations from Andesite Peak on Donner Summit and Tamarack Peak in the Mt. Rose backcountry showed a wet snow surface on all aspects up to the summit of Andesite at 8200 ft. and up to 9200 ft. on Tamarack Peak. The E-SE-S aspects up to 9800 ft. on Tamarack Peak held wet surface snow as well. Widespread loose wet roller balls and pinwheels occurred in both of these areas wherever wet surface snow existed. Tests including cornice drops, ski cuts, and snowpit tests on wind loaded test slopes in both areas did not reveal any cracking or other signs of lingering wind slab instabilities. 

Weather and CURRENT CONDITIONS
weather summary

.2 inches of precipitation fell on some parts of the forecast area along the Sierra Crest yesterday. In many places this precipitation fell as rain since snow levels remained above 8000 ft. Cloud cover decreased overnight and the south and southwest winds increased. The winds should continue to increase today ahead of another storm expected to reach the forecast area tomorrow afternoon. Cloud cover should also begin increasing today. By this afternoon the forecast calls for a chance for some scattered showers mainly north of I-80 with snow levels remaining above 7500 ft. Showers should become more widespread by tomorrow afternoon as the main part of the next storm pushes into the area. Snow level should also fall to between 6000 and 7000 ft. The forecast calls for up to 4 inches of new snow by the end of the day tomorrow above 8000 ft. 

CONDITIONS ALONG THE SIERRA CREST BETWEEN 8200 FT. AND 9200 FT. IN THE LAST 24 HOURS
Weather Station Map
Weather Station Table
6am temperature: 33 to 39 deg. F.
Max. temperature: 37 to 39 deg. F.
Average ridgetop wind direction: Southwest
Average ridgetop wind speed: 35 to 45 mph
Maximum ridgetop wind gust: 72 mph
New snowfall: Trace inches
Total snow depth: 71 to 104 inches
Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 7000 ft. to 8000 ft.
Thursday Thursday Night Friday
Weather: Mostly cloudy to cloudy with isolated showers in the morning and scattered showers in the afternoon. Snow level 7500 to 8000 ft. Cloudy with scattered showers. Snow level 7000 to 7500 ft. Cloudy with a chance of snow showers in the morning and snow showers becoming more likely and widespread in the afternoon.
Temperatures: 40 to 47 deg. F. 29 to 36 deg. F. 37 to 44 deg. F.
Mid Slope Winds: Southwest Southwest switching to south after midnight South
Wind Speed: 40 to 50 mph with gusts to 75 mph 30 to 35 mph with gusts to 55 mph increasing to 40 to 45 mph with gusts to 65 mph after midnight 35 to 45 mph with gusts to 65 mph
Expected snowfall: 0 0 up to 3
For 8000 ft. to 9000 ft.
Thursday Thursday Night Friday
Weather: Mostly cloudy to cloudy with isolated snow showers in the morning and scattered snow showers in the afternoon. Cloudy with scattered snow showers Cloudy with a chance of snow showers in the morning. Snow showers likely in the afternoon.
Temperatures: 37 to 44 deg. F. 28 to 35 deg. F. 33 to 40 deg. F.
Ridge Top Winds: Southwest Southwest switching to south after midnight South
Wind Speed: 70 to 80 mph with gusts to 110 mph 50 to 55 mph with gusts to 80 mph increasing to 60 to 65 mph with gusts to 100 mph after midnight 65 to 70 mph with gusts to 100 mph decreasing to 55 to 60 mph with gusts to 90 mph in the afternoon
Expected snowfall: 0 up to 1 up to 3
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.