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 Wednesday, December 20, 2006 at 6:54 am

A large diurnal temperature swing is expected to occur again today as our current spell of cold weather comes to an end. Easterly ridgetop winds have become light and variable overnight as the next storm system approaches the forecast area. Cloud cover will increase as the day progresses. Snowfall is expected overnight before warm air associated with the storm system causes snow levels to rise to around 7,500' during the day on Thursday.

The snowpack has become stable on the majority of aspects and elevations. Some very isolated pockets of shallow wind slab remain on NW aspects. Most above treeline N-NE-E aspects have been scoured back down to the uppermost crust in the snowpack This has put an end to wind transport of snow, despite continued moderate easterly winds yesterday morning. In all areas, snow surface conditions consist of either a hard surface crust or pockets of unconsolidated snow sitting on top of a supportable crust layer. Fair to good bonding has been observed at this layer interface throughout the forecast area. The areas of weakest bonding have been observed on recently wind loaded NW aspects. Despite some faceting of snow crystals near crust layers and in basal layers above 8,500' on northerly aspects, the snowpack is in good shape to handle additional new snow loading from the approaching storm system.

Avalanche danger is expected to increase overnight and into Thursday as a rain on new snow event occurs below 7,500'. New snow with expected accumulation rates around 2 inches per hour combined with strong ridgetop winds will cause an increase in avalanche danger for near and above treeline areas.

For today, avalanche danger is LOW for the vast majority of aspects at all elevations. Some very isolated pockets of MODERATE danger linger on recently wind loaded NW aspects, 37 degrees and steeper.

Brandon Schwartz , Avalanche Forecaster

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Today's Central Sierra Weather Observations:
0600 temperature at Sierra Crest (8,700 feet): 21 deg. F
Max. temperature at Sierra Crest past 24 hours: 23 deg. F
Average wind direction at Sierra Crest past 24 hours: easterly
Average wind speed at Sierra Crest past 24 hours: 25 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: 22 inches

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Mountain Weather Forecast For Today:
Partly cloudy skies
Temperature forecast for 8,000 to 9,000 feet: 31 - 37 deg. F
Ridgetop winds forecast for the Sierra Crest: northwesterly 10 - 15 mph, G 25 mph, increasing in the late afternoon
Snowfall expected in the next 24 hours: 1 - 3 inches

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2 Day Mountain Weather Forecast:
7000 to 8000 Feet
For today, partly cloudy skies with daytime highs 34 to 40 degrees F. Winds out of the west at 10 to 15 mph increasing in the late afternoon. Overnight lows 22 to 30 degrees F with mostly cloudy skies. Snowfall beginning after midnight. Westerly winds 20 to 30 mph. Thursday will be cloudy with rain and snow. Daytime highs 32 to 37 degrees F. Snow level initially around 6,000' rising to 7,500' during the day. Snow level is expected to lower below 6,000' late Thursday. Westsouthwesterly winds 20 to 35 mph with gusts to 65 mph.

Above 8000 Feet
For today, partly cloudy skies with daytime highs 31 to 37 degrees F. Winds out of the northwest at 10 to 15 mph increasing in the late afternoon. Overnight lows 24 to 34 degrees F with cloudy skies. Westerly winds 25 to 40 mph with gusts to 50 mph. Thursday will be cloudy with snow, heavy at times. Daytime highs 27 to 32 degrees F. Westsouthwesterly ridgetop winds 45 to 60 mph with gusts to 80 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:
	Wednesday:	Wednesday Night:	Thursday:
Weather:
Temperatures:	deg. F.	deg. F.	deg. F.
Wind direction:
Wind speed:
Expected snowfall:	O in.	O in.	O in.
For 8000-9000 ft:
	Wednesday:	Wednesday Night:	Thursday:
Weather:
Temperatures:	deg. F.	deg. F.	deg. F.
Wind direction:
Wind speed:
Expected snowfall:	O in.	O in.	O in.