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.

A change in the weather will occur today as cloud cover and southwest winds increase today ahead of an approaching weather system. A chance of snow showers exists for today, with the main period of snowfall expected to occur tonight. New snowfall amounts for the next 24 hours are forecast at 2 to 5 inches. After a period of light northeast winds through the day yesterday, ridgetop winds have shifted to the southwest overnight. Moderate wind speeds with gusts at 40 to 50 mph are expected to occur this afternoon. Air temperatures are expected to remain below freezing today in many areas above 8,000'.

Observations:

A skier triggered avalanche occurred yesterday outside the Sugar Bowl Ski Area boundary on Mt. Lincoln (Donner Summit area). The avalanche occurred at 7,600' on a SW aspect 40 to 45 degree slope. The crown measured 4 to 12 inches in most areas with a maximum height of 24 inches. The avalanche measured 600' wide and 900' long. The avalanche occurred when the skier encountered an area of wind deposited snow about 700' down from the summit. Partial burial occurred and the victim escaped without injury. Details on the snowpack are very limited, but initial reports indicate that the weak layer existed at the January 25 rain crust and the overlying slab was mainly high density storm snow with some additional wind transported snow from Wednesday night.

Other observations from around the forecast yesterday including Relay Peak (Mount Rose area), Ward Canyon (Blackwood Canyon area), and Mt. Tallac (Desolation Wilderness area) all indicated the presence of stable snowpack conditions (more info here). Snowpit data collected yesterday in Ward Canyon in below treeline terrain at 8,030' on a N aspect 31 degree slope noted the Jan 25 rain crust. Test results indicated it was an unlikely but not impossible weak layer at that location(pit profile). The only observations we have from aspects similar to yesterday's Mt. Lincoln event indicated the presence of a stable snowpack. However, these observations from Wednesday were made in the Mount Rose area on SE-S-SW aspects near and above treeline between 8,200' and 10,200'. This is above the elevation of the Jan 25 rain crust.

Avalanche concern #1: Recent avalanche event inconsistent with other field observations leads to increased uncertainty.

Avalanche activity similar to yesterday's Mt. Lincoln event involving the January 25 rain crust remains possible in isolated areas. This rain crust exists within the top 1 to 2 feet of the snowpack on all aspects below 8,200'. Failure on this type of weak layer can propagate far, creating wide avalanches. With so many other field observations indicating good stability of this layer, any activity today is expected to be isolated and most likely to occur in very steep complex terrain (lots of rock bands, cliffs, gully features, etc.).

Avalanche concern #2:

With some redistribution of snow caused by NE winds on Wednesday night, snow remains available for wind transport by today's increasing SW winds in near and above treeline terrain. Small shallow wind slabs may form today, mainly on N-NE-E aspects below cornice features. By this afternoon, these slabs may become large enough to present a hazard to backcountry travelers.

The bottom line:

Isolated pockets of MODERATE avalanche danger linger in wind affected areas above and below treeline, especially in complex terrain on all aspects, 37 degrees and steeper. These areas of instability will exist within larger areas of a seemingly stable snowpack.

Brandon Schwartz - Avalanche Forecaster, Tahoe National Forest

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

0600 temperature:	26 to 33 deg. F.
Max. temperature in the last 24 hours:	32 to 44 deg. F.
Average wind direction during the last 24 hours:	East shifting to southwest
Average wind speed during the last 24 hours:	18 mph
Maximum wind gust in the last 24 hours:	35 mph
New snowfall in the last 24 hours:	O inches
Total snow depth:	74 to 111 inches

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

For 7000-8000 ft:
	Friday:	Friday Night:	Saturday:
Weather:	Cloudy skies with a slight chance of snow showers.	Cloudy skies with scattered snow showers in the evening. Snow likely after midnight.	Cloudy skies with snow likely in the morning. Mostly cloudy skies with a chance of snow showers in the afternoon.
Temperatures:	32 to 39 deg. F.	22 to 27 deg. F.	24 to 29 deg. F.
Wind direction:	SW	S	SW
Wind speed:	10 to 15 mph	10 to 15 mph with gusts to 30 mph.	10 to 15 mph
Expected snowfall:	0 to 1 in.	1 to 4 in.	1 to 2 in.
For 8000-9000 ft:
	Friday:	Friday Night:	Saturday:
Weather:	Cloudy skies with a slight chance of snow showers.	Cloudy skies with scattered snow showers in the evening. Snow likely after midnight.	Cloudy skies with snow likely in the morning. Mostly cloudy skies with a chance of snow showers in the afternoon.
Temperatures:	27 to 34 deg. F.	16 to 21 deg. F.	17 to 22 deg. F.
Wind direction:	SW	S	SW
Wind speed:	10 to 15 mph increasing to 15 to 25 mph with gusts to 40 mph in the afternoon.	20 to 30 mph with gusts to 50 mph.	10 to 15 mph with gusts to 30 mph.
Expected snowfall:	0 to 1 in.	2 to 5 in.	1 to 3 in.