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.

Over the last 24 hours temperatures have plummeted and snow showers have dropped 2-4 inches of new snow on the mountains. In some areas slightly more snow fell and in others slightly less. The cold low pressure responsible for these changes also brought strong southwest winds to the area. These winds lasted through about midnight last night before they started to shift to the north and northeast. As the low pressure moves out of the area over the next 24 hours, snow showers should come to an end and the northeast winds should continue. The forecast calls for temperatures to remain cold for a few days in the wake of this system.

Recent Observations:

Recent observations across the forecast area have shown rain crusts on the northerly aspects and thick melt-freeze crusts on the southerly aspects. On the northerly aspects, a thin layer of soft weak snow (facets) rests above the rain crust in some areas with another layer of these facets below the rain crust in almost all areas. Near Polaris Point (below Stanford Rocks) yesterday, similar snowpack stratigraphy existed (snowpit, more info). The rain crust in this area did not support the weight of a skier. Other recent observations have revealed a more supportable and thicker rain crust. Snowpit tests on the facets below the rain crust indicated weakness in that layer. Below these shallow surficial weaknesses, a strong snowpack exists above the old December weak layers. Tests on these older weak layers yesterday showed that they continue to gain strength slowly, that fractures in those layers are unlikely to travel very far, and that transmitting force down to that depth remains very difficult.

Avalanche Concern #1: Wind Slabs

Strong winds combined with new snow have allowed wind slabs to form on some leeward aspects. The majority of these wind slabs should remain small, shallow, and only extend short distances away from ridgelines due to the small amounts of new snow available for wind transport. Most of these slabs should not hold enough snow to bury a person. In heavily wind loaded areas that received the most new snow, some isolated larger wind slabs may have formed on the near and above treeline leeward aspects. These slabs reside on top of firm crusts that make very efficient bed surfaces. Many of these crusts have thin layers of weak snow around them. Human triggering of these wind slabs will be possible today. The largest and most fragile wind slabs will exist on the most heavily wind loaded NW-N-NE-E-SE aspects in areas that received the highest snowfall amounts. Smaller wind slabs could also form on other aspects due to today's increased northeast winds.

Avalanche Problem #2: Loose Dry Avalanches:

The combination of cold dry snow on top of a smooth slippery surface will allow small loose snow sluffs to become possible today on steep slopes. This loose snow problem should remain shallow and surficial and not involve enough snow to bury a person. In areas that received the most new snow, a few of these sluffs could change one's course of travel and push one into areas with other consequences.

The bottom line:

On slopes steeper than 35 degrees, isolated pockets of MODERATE avalanche danger may exist on near and above treeline aspects due new wind slabs resting on frozen crusts. Small loose dry snow avalanches may also be possible on some steep slopes at all elevations today due new snow resting on frozen crusts.

Andy Anderson - Avalanche Forecaster, Tahoe National Forest

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

0600 temperature:	8-15 deg. F.
Max. temperature in the last 24 hours:	18-29 deg. F.
Average wind direction during the last 24 hours:	Southwest shifting to northeast after midnight
Average wind speed during the last 24 hours:	25-40 mph decreasing after midnight to 10-20 mph
Maximum wind gust in the last 24 hours:	57-79 mph
New snowfall in the last 24 hours:	2-4 inches
Total snow depth:	58-81 inches

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

For 7000-8000 ft:
	Friday:	Friday Night:	Saturday:
Weather:	Cloudy with snow showers	Mostly cloudy with scattered snow showers in the evening. Snow showers tapering off overnight	Partly Cloudy
Temperatures:	14-21 deg. F.	7-13 deg. F.	19-26 deg. F.
Wind direction:	North	Northeast	Northeast
Wind speed:	15-20 mph with gusts to 30 mph	15-25 mph with gusts to 35 mph	20-30 mph with gusts to 40 mph
Expected snowfall:	less than 2 in.	O in.	O in.
For 8000-9000 ft:
	Friday:	Friday Night:	Saturday:
Weather:	Cloudy with snow showers	Mostly cloudy with scattered snow showers in the evening. Snow showers tapering off overnight	Partly Cloudy
Temperatures:	13-19 deg. F.	6-12 deg. F.	17-23 deg. F.
Wind direction:	North to northeast	Northeast	Northeast
Wind speed:	20-25 mph with gusts to 40 mph	20-30 mph with gusts to 40 mph	20-30 mph with gusts to 45 mph
Expected snowfall:	less than 2 in.	O in.	O in.