THIS AVALANCHE FORECAST EXPIRED ON January 6, 2021 @ 6:59 am
Avalanche Forecast published on January 5, 2021 @ 6:59 am
Issued by Steve Reynaud - Tahoe National Forest

Heavy and wet new snow has loaded our weak snowpack structure.  Human triggered persistent slab and wind slab avalanches remain a concern for today.  Just because the storm has ended and it's a sunny day, doesn't mean that avalanches can't occur.  CONSIDERABLE avalanche danger will exist at all elevations.    

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: Persistent Slab
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Our current snowpack remains mostly shallow, variable, with multiple layers of concern.  The Dec. 11 persistent weak layer, the Dec. 25 near crust facets, and the potential for a buried surface hoar layer represent our main concerns within the snowpack.  While yesterdays storm was less than forecasted, it still dropped heavy, wet, dense, snow on top of these potential weak layers.  As the storm ended last evening, observations are limited and it's uncertain how these weak layers have adjusted to the additional snow load.  Today is a good day to tread lightly and use simple terrain if venturing out into the backcountry.  These weak layers have already caused avalanches that were deep with wide propagation.  Avalanches today could be large in size (D2 to D3), with wide propagation, and could be remotely triggered.  

Most avalanche accidents occur post storm when the sun comes out-like today.    If heading out, use low angle simple terrain that is not connected to steeper terrain above, below, or to the side.  Making a trip plan before you depart will help you and your group find appropriate terrain for today and more importantly- terrain that should be avoided.  Any whumpfing, cracking, slope failure, or avalanche activity will be major signs of instability.  If large avalanches due occur, they could run farther than anticipated, make sure you are not in an avalanche run out zone.  

Avalanche Problem 2: Wind Slab
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Large wind slabs formed yesterday during the storm on NW-N-NE-E-SE aspects in near and above treeline areas.  Wind slab avalanches along with fragile cornices failed easily as the storm increased intensity by midday.  SW winds have remained in the strong to gale force range throughout most of the night before decreasing early this morning.  Active wind loading would have continued in any areas that had snow available for transport.  Large fragile cornices with dense and deep wind slabs will be likely today.

Look for active wind loading or previous signs of wind transport when traveling through the backcountry. Blowing snow, snow surface scouring, and dense snow over less dense snow will all be signs of where wind slabs could exist.  Areas below large cornices and steep terrain below ridges will be of most concern for wind slab avalanches.  Make a plan to avoid travel below or near these areas of concern.   

recent observations
Submit Observations

* Cornice releases and wind slab avalanches occurred on Lincoln Ridge in the Yuba Pass area yesterday.  Snowpack tests did not show unstable results on any buried walk layers in this area.

* Unstable snowpack test results were reported from Tamarack Peak (Mt. Rose area) and Scout Peak (Echo Peak area) on buried weak layers. 

*  Rain on snow was reported from most locations yesterday, even up to around 9000' in the Mt. Rose area.  Gale force SW winds with challenging travel conditions were common.  

Weather and CURRENT CONDITIONS
weather summary

Yesterdays wet and windy storm has departed leaving heavy dense snow.  5 to 9'' of new snow fell along the Northern Sierra Crest above 7500', with 2 to 5'' of snow along the Southern Sierra Crest, and 5'' in the Mt. Rose area.  Snow totals decreased quickly below 7500' with a mostly rain/snow mix, with little accumulation below 6500-7000'.  Today brings sunny skies, warming temperatures, with decreasing SW/W winds.  A couple small storms are possible for this week with the next one expected on Wednesday night into Thursday.   

CONDITIONS ALONG THE SIERRA CREST BETWEEN 8200 FT. AND 9200 FT. IN THE LAST 24 HOURS
Weather Station Map
Weather Station Table
6am temperature: 16 to 25 deg. F.
Max. temperature: 28 to 32 deg. F.
Average ridgetop wind direction: SW
Average ridgetop wind speed: 40 to 80 mph
Maximum ridgetop wind gust: 191 mph
New snowfall: 2 to 9 inches
Total snow depth: 31 to 40 inches
Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 7000 ft. to 8000 ft.
Tuesday Tuesday Night Wednesday
Weather: Mostly sunny. Snow levels below 7000 feet. Chance of precipitation is 0%. Clear then becoming partly cloudy. Snow levels below 7000 feet. Chance of precipitation is 0%. Mostly cloudy. Slight chance of snow in the afternoon. Snow levels below 7000 feet. Chance of precipitation is 15%.
Temperatures: 36 to 41. deg. F. 23 to 29. deg. F. 38 to 43. deg. F.
Mid Slope Winds: Light winds. Light winds. Light winds.
Expected snowfall: No accumulation. | SWE = none. No accumulation. | SWE = none. No accumulation. | SWE = trace amounts.
For 8000 ft. to 9000 ft.
Tuesday Tuesday Night Wednesday
Weather: Mostly sunny. Snow levels below 7000 feet. Chance of precipitation is 0%. Partly cloudy then becoming mostly cloudy. Snow levels below 7000 feet. Chance of precipitation is 0%. Mostly cloudy. Slight chance of snow in the afternoon. Snow levels below 7000 feet. Chance of precipitation is 15%.
Temperatures: 33 to 38. deg. F. 21 to 26. deg. F. 34 to 39. deg. F.
Ridge Top Winds: West 15 to 25 mph with gusts to 40 mph in the morning becoming light. Light winds becoming southwest around 15 mph with gusts to 25 mph after midnight. Southwest around 15 mph. Gusts up to 25 mph increasing to 40 mph in the afternoon.
Expected snowfall: No accumulation. | SWE = none. No accumulation. | SWE = none. No accumulation. | SWE = trace amounts.
Disclaimer

This avalanche forecast is provided through a partnership between the Tahoe National Forest and the Sierra Avalanche Center. This forecast 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 forecast applies only to backcountry areas outside established ski area boundaries. This forecast describes general avalanche conditions and local variations always occur. This forecast expires 24 hours after the posted time unless otherwise noted. The information in this forecast is provided by the USDA Forest Service who is solely responsible for its content.

For a recorded version of the avalanche forecast call (530) 587-3558 x258