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 winds increased last night ahead of two cold fronts approaching the area. 15-20 inches of snow has fallen across the forecast area since yesterday afternoon. The southwest winds have averaged between 45 and 50 mph with gusts over 100 mph for most of the night. As the first of these fronts moves through the region this morning, expect temperatures and snow to continue falling. The winds and snowfall should decrease during the day. The second, colder front should arrive over the forecast area this afternoon bringing even colder temperatures. It will leave behind a mass of cold air that should push lows into the low single digits tonight. The winds should also start to shift to the north tonight as this second front exits. Cold temperatures and north winds should continue through tomorrow.

Observations:

Snowpit data, layer bonding tests, and general observations yesterday on Carson Pass and Lincoln Ridge (near Yuba Pass) showed a mostly stable snowpack in good shape to handle new loading. On Carson Pass a thin, wet, melt-freeze crust existed up to 8900 ft on the snow surface. Wet surface snow existed up to 7500' on Lincoln Ridge as well. On Mt. Judah in areas where more intense wind-loading continued to occur, 4-8 inch wind slabs that failed in response to ski cuts and small cornice drops had already formed on steep N-NE-E facing test slopes (photos, videos). Rain fell up to at least 7000 ft in this area yesterday. Expect to see evidence of natural avalanches that occurred last night in wind-loaded areas today.

Primary Avalanche Concern: Wind Slabs

Over the last 24 hours, new wind slabs have formed due to the strong winds and 15-20 inches of new snow. These wind slabs have formed faster than the bonds holding them to the snowpack. As more wind and snow impact the forecast area today, these wind slabs will continue to grow larger and more widespread. Natural avalanches due to these wind slabs overloading the weak bonds holding them to the snowpack have already occurred during the night. These kind of natural avalanches will remain possible today on steep slopes in the most heavily wind-loaded areas. On any slopes where new wind slabs exist that have not already avalanched, adding a person to the snowpack could easily overload those weak bonds and cause the wind slabs to fail. Human triggered avalanches will be likely on wind-loaded slopes today. Due to the strong and consistent winds expect these fragile wind slabs to extend into traditionally protected areas like trees, farther down-slope than usual, and in open areas below treeline. Large, deep, dangerous avalanches could result from failure of these wind slabs. The wind-loaded N-NE-E and cross-loaded NW and SE aspects will hold the largest and most fragile wind slabs. 

Secondary Avalanche Concern: Loose Snow

Human triggered loose snow sluffs will be likely on any steep slopes today. The colder NW-N-NE-E aspect at higher elevations will hold the best potential for larger loose snow sluffs. Even though these slides entrain less snow than slab avalanches, they can still 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).

The bottom line:

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

Andy Anderson - Avalanche Forecaster, Tahoe National Forest

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

0600 temperature:	21-24 deg. F.
Max. temperature in the last 24 hours:	27-29 deg. F.
Average wind direction during the last 24 hours:	Southwest
Average wind speed during the last 24 hours:	45-50 mph
Maximum wind gust in the last 24 hours:	109 mph
New snowfall in the last 24 hours:	15-20 inches
Total snow depth:	77-108 inches

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

For 7000-8000 ft:
	Wednesday:	Wednesday Night:	Thursday:
Weather:	Snow this morning tapering off to snow showers in the afternoon	Mostly cloudy with a slight chance of snow showers	Mostly cloudy with a slight chance of snow showers
Temperatures:	20-27 deg. F.	2-8 deg. F.	8-15 deg. F.
Wind direction:	Southwest	West shifting to the North	North
Wind speed:	20-30 mph with gusts to 45 mph	15-20 mph decreasing to 10-15 mph with gusts to 35 mph after midnight	10-15 mph with gusts to 25 mph in the afternoon
Expected snowfall:	5-9 in.	trace in.	trace in.
For 8000-9000 ft:
	Wednesday:	Wednesday Night:	Thursday:
Weather:	Snow this morning tapering off to snow showers in the afternoon	Mostly cloudy with a slight chance of snow showers	Mostly cloudy with a slight chance of snow showers
Temperatures:	16-23 deg. F.	0-6 deg. F.	8-14 deg. F.
Wind direction:	Southwest	Northwest	North
Wind speed:	45-60 mph with gusts to 95 mph decreasing to 30-40 mph with gusts to 75 mph in the afternoon	20-30 mph with gusts to 45 mph	10-15 mph with gusts to 25 mph increasing to 35 mph in the afternoon
Expected snowfall:	5-10 in.	trace in.	trace in.