Avalanche Advisory published on November 26, 2017 @ 8:03 am
Issued by Andy Anderson - Tahoe National Forest

Early season conditions update #8

Continue to use normal caution when traveling in the backcounrty. Rain, snow, and wind during the storm on Sunday and Monday could allow wind slabs, possible storm slab, or minor loose wet instabilities to form in some areas where enough snow accumulates. Near and above treeline terrain holds the best potential for these areas of instability especially in areas where significant wind-loading occurs. These instabilities should diminish during the week as the weather calms down.

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Above Treeline

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Near Treeline

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Below Treeline
Avalanche Problem 1: Wind Slab
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As new snow and wind impact the area during the next 24 hours, expect unstable wind slabs to form on some wind-loaded slopes. Some of these wind slabs could grow large enough during the night to pose a threat to backcountry travelers in specific areas where the most wind-loading occurs. 

Avalanche Problem 2: Loose Wet
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Rain on snow may create enough wet snow this afternoon for some loose wet instabilities to form. These should remain small and limited to areas with existing snow.

Avalanche Problem 3: Storm Slab
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Changes in precipitation intensity, temperature, winds, and other things during this storm may create some weaknesses in the storm snow allowing small isolated storm slabs to form in some more sheltered areas. These should remain limited to areas with an existing snowpack that covers up the trees, rocks, stumps, etc that may serve to anchor the snowpack in place.  

recent observations

* Despite significant melting this week, 2 to 3 ft. of snow still exists above 8,000' on most E-NE-N-NW aspects throughout the forecast area.  Below 7,200' to 7,800', the snowpack is shallow with a minimal amount of usable snow.  Bare ground exists in most areas below 7,000'.

* Snowpit data across the forecast area up to 10200 ft. indicates a well-bonded snowpack. Tests targeting the old snow at the bottom of the pack no longer show evidence of continued instability.

* Spring-like snow conditions exist in many areas with daytime warming creating soft wet snow on the surface on sun-exposed aspects

* Firm, icy surfaces exist on shaded aspects

See specific observations below for more info.

Weather and CURRENT CONDITIONS
weather summary

Clouds and winds have increased since yesterday heralding the arrival of the next winter storm. Temperatures should remain warm until colder air arrives over the region tonight.  The forecast calls for gale force south and southwest winds through tonight. Precipitation should start as rain with snow levels around 10000 ft. sometime this afternoon before changing over to snow during the night as snow levels fall down to below 6500 ft. by tomorrow morning. Above 7000 ft. most areas should see 6 to 12 inches of new snow by Monday morning with some places receiving up to 15 inches. Below 7000 ft. more of the precipitation will fall as rain. Once snow levels lower to lake level the storm could deposit 4 to 6 inches of snow at Lake Level. This storm should taper off on Monday. The forecast calls for cooler, breezy, and dry weather until Friday. Another storm may arrive over the region late Friday. 

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 a chance of rain in the afternoon. Snow levels starting at 10000 ft. and dropping to 8500 ft. in the afternoon. Cloudy with rain and snow. Snow levels starting at 8000 ft. dropping to 6500 ft. after midnight. Mostly cloudy with snow likely in the morning. Snow showers tapering off throughout the day with only a slight chance of snow in the afternoon. Snow levels below 6000 ft.
Temperatures: 48 to 54 deg. F. 28 to 33 deg. F. 33 to 38 deg. F.
Wind Direction: South Southwest Northwest
Wind Speed: 25 to 35 mph with gusts to 60 mph increasing to 30 to 50 mph with gusts to 100 mph in the afternoon 30 to 40 mph with gusts to 80 mph decreasing to 20 to 35 mph with gusts to 70 mph after midnight 15 to 20 mph with gusts to 40 mph decreasing to gusts to 25 mph in the afternoon
Expected snowfall: Snow: 0 in. | Rain: .25 - .4 in. 3 to 5 in. 1 to 3 in.
For 8000 ft. to 9000 ft.
Sunday Sunday Night Monday
Weather: Mostly cloudy with a chance of rain and snow in the afternoon. Snow levels starting at 10000 ft. and dropping to 8500 ft. in the afternoon. Cloudy with rain in the evening and snow through the night. Snow levels starting at 8000 ft. dropping to 6500 ft. after midnight. Mostly cloudy with snow likely in the morning. Snow showers tapering off throughout the day with only a slight chance of snow in the afternoon. Snow levels below 6000 ft.
Temperatures: 43 to 49 deg. F. 24 to 30 deg. F. 30 to 35 deg. F.
Wind Direction: South Southwest West shifting to the Northwest in the afternoon
Wind Speed: 45 to 60 mph with gusts to 85 mph increasing to 50 to 70 mph with gusts to 125 mph in the afternoon 45 to 65 mph with gusts to 130 mph decreasing to 30 to 50 mph with gusts to 110 mph after midnight 20 to 30 mph with gusts to 60 mph decreasing to 15 to 20 mph with gusts to 35 mph in the afternoon
Expected snowfall: up to 3 in. 4 to 8 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