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 Monday, December 11, 2006 at 7:00 am

Our SAC Ski Day tickets are now available. This is an excellent opportunity for you to make a donation to SAC by purchasing a heavily discounted lift ticket that was donated to us by the ski area. All of the proceeds from your ticket purchase go to SAC and you get to go skiing. This year the tickets can be bought online thanks to Snowbomb.com (just click on the link above). Our first ski day is at Mt. Rose on December 17th. We hope to see you there.

The third disturbance of this storm cycle is forecasted to pass mostly to the north of us and bring a little accumulation to our area. The west southwest winds will not be as intense today, but they will pick back up again tonight as the disturbance moves in. The winds stayed strong until about midnight last night and continued transport a large percentage of the newly fallen snow onto lee slopes. Even though they are calmer now, there will still be windloading occurring today. Air temperatures should remain cool until Wednesday when we will see a warming trend ahead of the next storm cycle.

The SW winds loaded the new snow into the the north through east facing aspects. In some areas the 10" of snow that fell turned into 24" on the leeward slopes. The existing snowpack that the storm snow fell on is highly varied. The upper elevation (above 8200') NW-N-NE-E starting zones that were scoured by the east winds exhibited surface conditions that ranged from bare ground to a cold, hard surface crust. On the areas of bare ground and halfway covered obstacles the storm snow is well anchored by rocks, shrubs and trees. On the areas where the hard surface crust was present, the storm snow bonded poorly to the crust and slides easily. There is also a rimed crystal layer within the new snow that serves a failure layer. Near Kirwood above 9000' yesterday ski cutting triggered several soft slab avalanches that failed at the interface between the old crust and the new snow. We also observed some very localized cracking and compression test failures at this interface as well as on the rimed crystal layer within the new snow. However, due to the variable extent of this old surface crust it is hard for these areas of instability to connect to each other and create large avalanches. They simply remain isolated small pockets of instability that are confined to small areas of steep windloaded slopes. At the lower elevations the crust is less prevalent and the snowpack was warmer when the new snow fell on it. The warmer unconsolidated snow allowed the new snow to bond nicely to the existing snowpack. It is much less likely to see any activity in the lower elevations.

Near and above treeline, overall the avalanche danger is LOW with small isolated pockets of MODERATE avalanche danger on wind loaded NW-N-NE-E aspects, 35 degrees and steeper. Below treeline, avalanche danger is LOW. Remember that even though you are unlikely to trigger anything large, a small avalanche can be disastrous depending on the terrain. Watch out for anything that could push you over a cliff, into a creek, or bury you in a small gully. These types of terrain traps will magnify the consequences of any avalanche.

Keep in mind that the overall snowpack is very shallow. You will hit rocks on your skis, snowboard, or snowmobile when you venture off of the snowpacked roads. Getting hurt this time of year makes for a very long winter. Travel at slow speeds to minimize damage to yourself and your equipment. Your best option for recreation remains xc style touring on the higher elevation roads.

Andy Anderson , Avalanche Forecaster

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Today's Central Sierra Weather Observations:
0600 temperature at Sierra Crest (8,700 feet): 22 deg. F
Max. temperature at Sierra Crest past 24 hours: 25 deg. F
Average wind direction at Sierra Crest past 24 hours: west southwesterly
Average wind speed at Sierra Crest past 24 hours: 20 mph
Maximum wind gust at Sierra Crest past 24 hours: 81 mph
New snow fall at 8,200 feet past 24 hours: trace
Total snow depth at 8,200 feet: 15 inches

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Mountain Weather Forecast For Today:
Mostly cloudy skies with isolated snow showers.
Temperature forecast for 8,000 to 9,000 feet: 37 deg. F
Ridgetop winds forecast for the Sierra Crest: west southwesterly at 15 mph, G 25 mph
Snowfall expected in the next 24 hours: 2-5 inches

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2 Day Mountain Weather Forecast:
7000 to 8000 Feet
For today, cloudy skies with isolated snow showers in the afternoon. Daytime high of 37 degrees F. Overnight lows around 23 degrees F. Snow showers with up to 2" accumulation. Tuesday will be mostly cloudy with daytime highs 34 to 39 degrees F. Snow showers with up to 3 " accumulation. Winds out of the west at 25-35 MPH with gusts to 50 MPH

Above 8000 Feet
For today, cloudy skies with isolated snow showers in the afternoon. Daytime highs 29-35 degrees F. Overnight lows around 20 degrees F. Snow showers with up to 2" accumulation. Tuesday will be mostly cloudy with daytime highs 34 to 39 degrees F. Snow showers with up to 3 " accumulation. Winds out of the west at 30-40 MPH with gusts to 65 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.