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.

This advisory was posted on December 23, 2007 7:00 AM
Click here for a detailed map of the SAC forecast area

2_moderate
Today's Advisory:
Along the Sierra Crest the avalanche danger is LOW at all elevations and aspects. In the Mount Rose area near and above treeline, the avalanche danger is LOW with pockets of MODERATE danger on N-NE-E aspects, 35 degrees and steeper. Below treeline the avalanche danger is LOW.

A low pressure system passing to the north of the forecast area today should bring mostly cloudy skies. The winds should should shift more to the northwest and west. Some isolated snow showers are possible overnight and tomorrow. Another system approaching the forecast area should cause the temperatures to fall and the wind to shift to the southwest by Monday afternoon.

Layer bonding tests along the Sierra Crest indicate a strengthening trend. This trend is more gradual in the Mount Rose area where a more developed layer of facets (weak, sugary snow grains) exists. Forming strong bonds between these facets and the layers above them will be a slow process. The current weather (warmer air temperatures and calmer winds) should help the snowpack to consolidate and help this strengthing trend continue today.

Stiff wind slabs continue to form as the wind transports the same snow grains back and forth. These slabs are more likely to fail once a person is already committed on a slope rather than when they first enter a slope. This reduces the potential to escape off the edge of an avalanche and increases the potential for burial. These slabs are more likely to be an issue in the Mount Rose area where they sit on top of a layer of facets.
Along the Sierra Crest avalanche activity is unlikely today. In the Mount Rose area human triggered avalanches are still possible today near and above treeline on N-NE-E slopes steeper than 35 degrees where new snow and stiff wind slabs sit on top of a layer of faceted snow. Even though avalanche activity is unlikely below treeline, it is possible if all of the ingredients combine in just the right manner. Any triggerable instability below treeline in the Mount Rose area should occur on small and isolated pockets of steep, open terrain where there are few anchors to support the snowpack.

The bottom line: Along the Sierra Crest the avalanche danger is LOW at all elevations and aspects. In the Mount Rose area near and above treeline, the avalanche danger is LOW with pockets of MODERATE danger on N-NE-E aspects, 35 degrees and steeper. Below treeline the avalanche danger is LOW.

Please send us your snow, weather, and avalanche observations by clicking the submit observations link on our contact page.

Andy Anderson, Avalanche Forecaster

Today's Central Sierra Weather Observations:
0600 temperature at Sierra Crest (8,700 feet): 32 deg. F
Max. temperature at Sierra Crest past 24 hours: 37 deg. F
Average wind direction at Sierra Crest past 24 hours: Northwest
Average wind speed at Sierra Crest past 24 hours: 10 mph
Maximum wind gust at Sierra Crest past 24 hours: 43 mph
New snow fall at 8,200 feet past 24 hours: 0 inches
Total snow depth at 8,200 feet: 32 inches
Mountain Weather Forecast For Today:
Mostly cloudy skies.
Temperature forecast for 8,000 to 9,000 feet: 32 to 38 deg. F.
Ridgetop winds forecast for the Sierra Crest: Northwest at 10 to 15 mph shifting to the southwest with gusts to 30 mph.
Snowfall expected in the next 24 hours: 0 inches
2 Day Mountain Weather Forecast:

7000 to 8000 Feet:
Today, mostly cloudy skies with daytime highs 37 to 42 deg. F. West winds at 10 mph.

Tonight, mostly cloudy skies with with a chance of snow showers. Overnight lows 25 to 30 deg. F. West winds at 10 to 15 mph shifting to the southwest with gusts to 35 mph after midnight.

For Monday, mostly cloudy skies with with a chance of snow showers. Daytime highs 30 to 35 deg. F. Southwest winds at 15 to 25 mph shifting to the northwest at 10-20 mph with gusts to 40 mph by the afternoon.

Above 8000 Feet:
Today, mostly cloudy skies with daytime highs 32 to 38 deg. F. Winds out of the northwest at 10 to 15 mph shifting to the southwest with gusts to 30 mph.

Tonight, mostly cloudy skies with with a chance of snow showers. Overnight lows 25 to 30 deg. F. Southwest winds at 10 to 15 mph shifting to the west at 25 to 35 mph with gusts to 60 mph after midnight.

For Monday, mostly cloudy skies with with a chance of snow showers. Daytime highs 27 to 32 deg. F and dropping to 23 to 27 deg. F. by the afternoon. West winds at 30 to 45 mph shifting to the northwest at 20-30 mph with gusts to 60 mph by the afternoon.

The bottom line:

Andy Anderson - Avalanche Forecaster, Tahoe National Forest

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

0600 temperature:	deg. F.
Max. temperature in the last 24 hours:	deg. F.
Average wind direction during the last 24 hours:
Average wind speed during the last 24 hours:	mph
Maximum wind gust in the last 24 hours:	mph
New snowfall in the last 24 hours:	O inches
Total snow depth:	inches

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

For 7000-8000 ft:
	Sunday:	Sunday Night:	Monday:
Weather:
Temperatures:	deg. F.	deg. F.	deg. F.
Wind direction:
Wind speed:
Expected snowfall:	O in.	O in.	O in.
For 8000-9000 ft:
	Sunday:	Sunday Night:	Monday:
Weather:
Temperatures:	deg. F.	deg. F.	deg. F.
Wind direction:
Wind speed:
Expected snowfall:	O in.	O in.	O in.