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.

Snowfall and strong winds continue throughout the forecast area this morning. Remote sensors are reporting 4 to 6 inches of accumulation in areas north of Hwy 50 and 2 to 4 inches of accumulation south of Hwy 50. An additional 3 to 6 inches is expected to fall across the forecast area, mainly during the morning hours. Ridgetop winds remain strong out of the southwest this morning, but are expected to decrease to moderate in speed this afternoon.

Observations:

Observations were made yesterday in a variety of locations around the forecast area. In the Carson Pass area, three small skier triggered avalanches were reported to have occurred around 1 pm on NE aspect, above treeline terrain on Round Top Peak and Sisters Peak. In the Mount Rose area, minor cracking was observed near ridgelines with a few very small (size D1) avalanches reported in steep rocky areas near treeline on northerly aspects. In the Donner Summit and Yuba Pass areas, good stability was observed with only minor skier triggered sluffing of new snow occurring on steep N-NE-E aspects near treeline. Significant wind transport of snow was observed during the afternoon hours as ridgetop winds increased ahead of the current weather system. Observations tracking the October 19 basal layer that exists below treeline on NW-N-NE aspects above 7,700' show increasing strength of this layer in many locations. The most recent observations to show that fracture propagation on this layer remains possible were December 26 on Waterhouse Peak (Luther Pass area) and December 24 on Deep Creek Peak (Deep Creek area). More specific info on each of these observations can be viewed by clicking here. This morning, data collected at the snow study plot at Alpine Meadows Ski Area revealed a top heavy slab over yesterdays low density new snow with a clean, planar (Q1) shear at the interface of the two layers. Squaw Valley Professional Ski Patrol reported drifts up to 2 feet deep below ridgelines.

Avalanche concern #1:

Unstable slab formation occurring near and above treeline due to wind loading on NW-N-NE-E-SE aspects. The combination of wind transported snow yesterday afternoon and wind loaded new snow overnight is expected to have created unstable slabs 1 to 2+ feet deep below ridgelines and cornice features. Natural avalanches are possible today. Human triggered avalanches are likely in these areas. Avalanches large enough to bury or injure a person are possible.

Avalanche concern #2:

Deep slab instability involving the Oct 19 facet layer near the base of the snowpack is unlikely but not impossible in isolated areas below treeline on NE wind protected NW-N-NE aspects above 7,700'. Very strong snow in the middle and upper portions of the snowpack has kept this layer from failing in areas where it remains weak, keeping human triggering of this weak layer an unlikely event.

The bottom line:

Near and above treeline, avalanche danger is CONSIDERABLE on NW-N-NE-E-SE aspects, 35 degrees and steeper. Below treeline, avalanche danger is MODERATE in open areas on NW-N-NE-E-SE aspects, 35 degrees and steeper.

Brandon Schwartz - Avalanche Forecaster, Tahoe National Forest

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

0600 temperature:	22 deg. F.
Max. temperature in the last 24 hours:	23 to 25 deg. F.
Average wind direction during the last 24 hours:	Southwest
Average wind speed during the last 24 hours:	45 mph
Maximum wind gust in the last 24 hours:	91 mph
New snowfall in the last 24 hours:	2 to 6 inches
Total snow depth:	38 to 63 inches

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

For 7000-8000 ft:
	Wednesday:	Wednesday Night:	Thursday:
Weather:	Cloudy skies with snow, decreasing during the afternoon.	Cloudy skies with a chance of snow showers.	Cloudy skies with a chance of snow.
Temperatures:	25 to 30 deg. F.	17 to 24 deg. F.	30 to 35 deg. F.
Wind direction:	SW shifting to W	SW	SW
Wind speed:	20 to 30 mph with gusts 40 to 50 mph.	Around 10 mph in the evening, becoming light.	Up to 10 mph in the morning. Winds increasing to 10 to 15 mph with gusts to 35 mph in the afternoon.
Expected snowfall:	3 to 6 in.	0 to trace in.	Trace to 1 in.
For 8000-9000 ft:
	Wednesday:	Wednesday Night:	Thursday:
Weather:	Cloudy skies with snow, decreasing during the afternoon.	Cloudy skies with a chance of snow showers.	Cloudy skies with a chance of snow.
Temperatures:	22 to 27 deg. F.	17 to 22 deg. F.	25 to 30 deg. F.
Wind direction:	SW shifting to W	W	W shifting to SW
Wind speed:	30 to 40 mph with gusts to 60 mph. Winds decreasing to 20 to 30 mph with gusts to 45 mph in the afternoon.	10 to 20 mph with gusts to 35 mph.	10 to 20 mph with gusts to 35 mph in the morning. Winds increasing to 20 to 30 mph with gusts to 55 mph in the afternoon.
Expected snowfall:	3 to 6 in.	0 to trace in.	Trace to 1 in.