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 31, 2007 6:38 AM
Click here for a detailed map of the SAC forecast area

low avalanche danger
Today's Advisory:

Avalanche danger is LOW for all elevations and aspects. Normal caution is advised.

A high pressure system over the forecast area should bring sunny skies and gradually warming temperatures to the forecast area over the next few days. Last night the winds shifted to the east and should continue through today before tapering off tonight. Tomorrow the winds should be calmer and return to the southwest.

Even though the winds are expected to be moderate today, they should still be able to move some snow. This transport will cause the few small cornices, pillows, and wind slabs that formed on the most heavily wind loaded N-NE-E aspects above treeline to shrink as they are scoured by the winds. These features should pose even less of a threat to backcountry travelers today. Clear, sunny, warmer weather may cause some pinwheels and roller balls to form today on the S-SW-W aspects. The low sun angle and east/northeast winds should keep the snow surface fairly cold on the more northerly aspects.

Overall the snowpack across the forecast area is mostly stable. Some sintering (a process that forms bonds between snow grains) and rounding has started to occur in the snowpack along the crest. Snow pit data and layer bonding tests continue to show these bonds gaining strength both within snowpack layers and between snowpack layers. A few layers and interfaces in the snowpack could still behave as weakness during the next storm. In the upper layers of the snowpack several crust layers exist that have not fully bonded to the layers above and below them. Facets (weak, sugary snow grains) that have formed in the lower layers of the snowpack will be slow to bond to each other and the layers above them. Nice weather forecast over the next few days should provide the perfect opportunity to go out dig around in the snow, check these layers out, and see what the snow stratigraphy looks like in your favorite backcountry areas.

The sheltered north aspects still have some nice unconsolidated snow on them. A mix of melt-freeze crusts, wind crusts, dense snow, and wind scoured surfaces exists on most other aspects. A melt-freeze crust formed on the S-SW-W-NW aspects below 8500' yesterday and should continue expand its range today. In the most exposed areas above treeline the changing winds have scoured almost all aspects over the last 10 days. This scouring resulted in a variable, shallow snowpack in these areas.

The bottom line: Avalanche danger is LOW for all elevations and aspects. Normal caution is advised.

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): 26 deg. F
Max. temperature at Sierra Crest past 24 hours: 27 deg. F
Average wind direction at Sierra Crest past 24 hours: Southwest shifting to northeast and east
Average wind speed at Sierra Crest past 24 hours: 20 mph
Maximum wind gust at Sierra Crest past 24 hours: 53 mph
New snow fall at 8,200 feet past 24 hours: 0 inches
Total snow depth at 8,200 feet: 31 inches
Mountain Weather Forecast For Today:
Sunny.
Temperature forecast for 8,000 to 9,000 feet: 32 to 37 deg. F
Ridgetop winds forecast for the Sierra Crest: Northeast at 10 to 20 mph shifting to the east with gusts to 35 mph.
Snowfall expected in the next 24 hours: 0 inches
2 Day Mountain Weather Forecast:

7000 to 8000 Feet:
Today, sunny skies with daytime highs 35 to 40 deg. F. East winds at 5 to 10 mph with gusts to 25 mph.

Tonight, clear skies with overnight lows in the 30's deg. F. and light winds.

For Tuesday, sunny skies with a few thin, high clouds. Daytime highs 40 to 45 deg. F. Southwest winds at 10 to 15 mph.

Above 8000 Feet:
Today, sunny skies with daytime highs 32 to 37 deg. F. Northeast winds at 10 to 20 mph with gusts to 35 mph shifting to the east at 10 to 15 mph this afternoon.

Tonight, clear skies with overnight lows 27 to 34 deg. F. Winds out of the southeast at 10 to 15 mph.

For Tuesday, sunny skies with a few thin, high clouds. Daytime highs 37 to 42 deg. F. Southwest winds at 10 to 25 mph.

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