THIS AVALANCHE ADVISORY EXPIRED ON January 21, 2017 @ 6:50 am
Avalanche Advisory published on January 20, 2017 @ 6:50 am
Issued by Steve Reynaud - Tahoe National Forest

Considerable avalanche danger will continue throughout the forecast area as another storm impacts our region.  Wind slab and storm slab avalanche problems will be very likely at all elevations.  Natural triggered avalanches will be possible and human triggered avalanches will be likely.  Dangerous avalanche conditions exist.  Conservative decision making and terrain choices are critical today.

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: Wind Slab
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Strong to gale force S/SW winds will form wind slabs on W-NW-N-NE-E-SE aspects near treeline and above treeline.  In some areas, these wind slabs will continue to build in size from yesterdays storm creating potential large and destructive wind slab avalanches.

Avoid steep wind loaded terrain.  Look for blowing snow, cornice formation and wind pillows as clues to where wind slabs exist.

Avalanche Problem 2: Storm Slab
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Storm slab avalanches will be likely on all aspects near treeline and below treeline today.  An additional 8 to 12'' of new storm snow is forecasted above 7000'.  This new storm snow will have difficulty bonding to our existing snowpack and there could also be weakness within the new storm snow.

Signs of storm snow instabilities could be snow surface cracking, snow collapsing, and whumpfing.  Avoid slopes steeper than 30 degrees in areas where signs of unstable storm slabs are present.

recent observations

Observations were made and received from Jakes Peak (West Shore area) and from Shirley Canyon (Squaw Valley area).  Reactive skier triggered storm slab avalanches occurred at both locations with many natural storm slab avalanches observed.  These storm slabs were in the 6 to 12'' range and grew larger throughout the day.  On Jakes Peak, snowpack tests showed additional weakness deeper within the storm snow but no avalanche activity was observed on these deeper layers.  Moderate to strong snowfall continued throughout the morning and into the afternoon on the West Shore with storm snow approaching 2 feet at the higher elevations. 

Weather and CURRENT CONDITIONS
weather summary

A winter storm warning is in effect until 4am Monday.  8 to 12'' are forecasted above 7000' today with strong to gale force winds from the S/SW.  The heaviest snowfall today should occur between 6am and 6pm with snowfall rates up to and exceeding 1''/hour.  There will be a slight break/decreasing snow on Saturday afternoon.  Then a major powerful winter storm will impact the region Saturday night through Sunday.  In total, this 3 part storm could bring 2 to 6+ feet of snow to the area.

Weather observations from along the Sierra Crest between 8200 ft. and 8800 ft.
0600 temperature: 19 to 24 deg. F.
Max. temperature in the last 24 hours: 26 deg. F.
Average wind direction during the last 24 hours: SW
Average wind speed during the last 24 hours: 40 to 50 mph
Maximum wind gust in the last 24 hours: 108 mph
New snowfall in the last 24 hours: 7 to 12 inches
Total snow depth: 95 to 124 inches
Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 7000 ft. to 8000 ft.
Friday Friday Night Saturday
Weather: Cloudy. Snow. Cloudy. Snow. Cloudy. Snow showers in the morning then scattered snow showers in the afternoon.
Temperatures: 25 to 30 deg. F. 17 to 22 deg. F. 24 to 29 deg. F.
Wind Direction: S SW SW
Wind Speed: 20 to 30mph with gusts to 60mph. 15 to 25mph with gusts to 50mph. 20 to 30mph with gusts to 55mph.
Expected snowfall: 8 to 12 in. 5 to 10 in. 4 to 8 in.
For 8000 ft. to 9000 ft.
Friday Friday Night Saturday
Weather: Cloudy. Snow. Cloudy. Snow. Cloudy. Scattered snow showers.
Temperatures: 21 to 26 deg. F. 15 to 20 deg. F. 20 to 25 deg. F.
Wind Direction: S SW SW
Wind Speed: 30 to 45mph. Gusts to 95mph decreasing to 80mph in the afternoon. 20 to 35mph. Gusts to 70mph decreasing to 60mph after midnight. 25 to 45mph with gusts to 75mph.
Expected snowfall: 8 to 12 in. 5 to 10 in. 4 to 8 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