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.

Snow showers and winds continued through yesterday adding another 5-8 inches of snow to the mountains above 7000 ft. 20-27 inches of snow has fallen across the forecast area since Tuesday afternoon. As the low pressure moved out of the area last night, snow showers tapered off, the cold air settled in, and the winds decreased and shifted to the northwest and northeast. A high pressure ridge off the CA coast should allow this northerly flow to continue today. The winds should increase today then decrease again tonight and tomorrow as this ridge settles over the area. Temperatures should remain cold with daytime highs in the teens today and tomorrow and overnight lows in the single digits.

Observations:

On Andesite Ridge and along Donner Pass, natural avalanches released overnight on Tuesday and early Wednesday morning near the base of the storm snow on wind-loaded, N-NE-E facing slopes steeper than 37 degrees with 2 ft deep crowns (photos). Reports of other similar natural avalanches that also occurred in that time frame came in from along the Sierra Crest. No other natural avalanches that released during the day yesterday were reported. However, the wind slabs did remain sensitive to skier-triggering yesterday. Ski cuts and cornice drops on wind-loaded slopes caused similar sized avalanches on 38-40 degree, NE-E facing slopes near treeline on Andesite Ridge at noon (video). In the Mt Rose area, a similar slide released due to a washing-machine-sized cornice dropped onto a wind-loaded, 38-40 degree, N facing slope at 12:15 (photos, video). Observers also reported shooting cracks and unstable test results in both these areas.

Primary Avalanche Concern: Wind Slabs

Even though natural activity due to the failure of the wind slabs formed during the storm has become less likely, large, deep, dangerous, human-triggered avalanches involving these wind slabs remain likely in wind-loaded areas today. The strong and consistent winds during the storm deposited these fragile wind slabs in unusual areas. Even traditionally protected areas like trees, farther down-slope than usual, and open areas below treeline could hold these fragile wind slabs. The most heavily wind-loaded N-NE-E and cross-loaded NW and SE aspects will hold the largest and most fragile wind slabs. As the north winds increase today, these slabs will become more stiff and stubborn. They could start to break above the person who triggers them or when the second or third person descends a wind-loaded slope.

The increased northerly winds will also transport snow onto the W-SW-S-SE aspects and form new, fragile wind slabs on these aspects. These wind slabs should remain smaller and limited to open slopes near ridgelines where the most wind transport occurs due to the northerly winds. Human-triggering of these new wind slabs will become possible today. Avalanches resulting from these slabs can push someone into an area that could have serious consequences like over a cliff, into a gully or creek, or into trees or other obstacles (terrain traps).

Secondary Avalanche Concern: Loose Snow

Human triggered loose snow sluffs will be possible on any steep slopes today. The colder NW-N-NE-E aspects will hold the best potential for larger loose snow sluffs. Even though these slides entrain less snow than slab avalanches, they can also push people into terrain traps.

The bottom line:

Near and above treeline, MODERATE avalanche danger exists on all aspects with pockets of CONSIDERABLE danger on NW-N-NE-E-SE aspects on slopes steeper than 35 degrees. Below treeline, MODERATE danger exists on NW-N-NE-E-SE aspects with pockets of MODERATE danger on S-SW-W aspects on slopes steeper than 35 degrees.

Andy Anderson - Avalanche Forecaster, Tahoe National Forest

Weather Observations from along the Sierra Crest between 8200 ft and 8800 ft:

0600 temperature:	4-6 deg. F.
Max. temperature in the last 24 hours:	23-27 deg. F.
Average wind direction during the last 24 hours:	West southwest shifting to the Northeast yesterday evening
Average wind speed during the last 24 hours:	Southwest 40-50 mph - Northeast 15 mph
Maximum wind gust in the last 24 hours:	94 mph
New snowfall in the last 24 hours:	5-8 inches
Total snow depth:	79-108 inches

Two-Day Mountain Weather Forecast - Produced in partnership with the Reno NWS

For 7000-8000 ft:
	Thursday:	Thursday Night:	Friday:
Weather:	Mostly cloudy with isolated snow showers	Partly cloudy becoming mostly cloudy after midnight	Mostly cloudy
Temperatures:	15-21 deg. F.	2-8 deg. F.	17-24 deg. F.
Wind direction:	North	North	North
Wind speed:	10-15 mph with gusts to 30 mph	10-15 mph with gusts to 25 mph	10 mph decreasing in the afternoon
Expected snowfall:	O in.	O in.	O in.
For 8000-9000 ft:
	Thursday:	Thursday Night:	Friday:
Weather:	Mostly cloudy with isolated snow showers	Partly cloudy becoming mostly cloudy after midnight	Mostly cloudy
Temperatures:	9-17 deg. F.	0-6 deg. F.	16-22 deg. F.
Wind direction:	North	North shifting to the northwest	North
Wind speed:	25-40 mph with gusts to 60 mph	20-35 mph with gusts to 60 mph decreasing to 15-25 mph with gusts to 30 mph after midnight	15-20 mph with gusts to 35 mph decreasing to around 10 mph in the afternoon
Expected snowfall:	O in.	O in.	O in.