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 Tuesday, December 19, 2006 at 6:51 am

Thanks to everyone who came out yesterday to support the avalanche center. We really appreciate all of you who have donated funds to us and who bought Mt. Rose tickets. Thanks to all of you yesterday was a financial success! We still don't have enough money to cover costs for the season yet, but with yesterday's event we will be able to keep the center going at full speed through our next fundraiser. Our next fundraiser is another ski day on January 21st at Kirkwood. Tickets for that day will go on sale a couple of weeks prior to the 21st. Your donations and support are what keeps the avalanche center going, thanks!

The ridge of cold high pressure is starting to move east. By Wednesday night the next low pressure system will start to replace it. This low should be in place by Thursday morning and is supposed to bring more snow with it. Temperatures will remain cold today, but they will start to warm up a little before the storm system arrives. The strong east northeast winds persisted through the night, but are forecasted to diminish today and start shifting to the west southwest ahead of Thursday's storm.

The east northeast winds scoured our N-NE-E starting zones and deposited the snow onto the S-SW-W-NW aspects. On the NW slopes these wind slabs are very tender. On several NW test slopes yesterday, there were slabs up to 8 inches deep and 40 feet wide that failed due to a skier's weight. None of these slabs ran very far or propagated across a wider area because of the widespread variation in snow depth and anchors on the slope. These pockets of instability will persist today on any wind loaded NW aspect steeper than 35 degrees. Even though they are small, they are certainly capable of knocking you off your feet, pushing you over a cliff, or into rocks/trees, or filling up a gully.

On the N-NE-E aspects the wind left behind the hard melt-freeze crust. While the temperatures remain cold, it will be very hard for any new snow to bond to this crust, and the existing snow will start to weaken again. On many of our northerly aspects and more shaded slopes, near surface and near crust faceting is starting. The longer that the weather stays cold and clear, the more widespread and well developed these layers will be. Without deep snow cover to insulate the snow grains within the pack, faceting will also start occurring in the layers that have already been buried. Above 8500' the depth hoar and near crust facets will continue to mature and weaken. The strong melt-freeze crust above these layers will also start to lose strength. Even the strong refrozen snowpack below 8500' will start to slowly facet in this weather. The warming trend ahead of our next storm should help reverse some of this weak layer formation, but we will still have to watch these layers carefully.

Near and above treeline, avalanche danger is LOW with pockets of Moderate on NW aspects that are windloaded and steeper than 35 degrees. Below treeline, avalanche danger is LOW.

Andy Anderson , Avalanche Forecaster
Today's Central Sierra Weather Observations:
0600 temperature at Sierra Crest (8,700 feet):
9 deg. F
Max. temperature at Sierra Crest past 24 hours:
17 deg. F
Average wind direction at Sierra Crest past 24 hours:
east northeast
Average wind speed at Sierra Crest past 24 hours:
50 mph
Maximum wind gust at Sierra Crest past 24 hours:
101 mph
New snow fall at 8,200 feet past 24 hours:
0 inches
Total snow depth at 8,200 feet:
24 inches
Mountain Weather Forecast For Today:
Sunny and cold.
Temperature forecast for 8,000 to 9,000 feet:
26 deg. F
Ridgetop winds forecast for the Sierra Crest:
northeast 25- 35 mph, G 45 mph diminishing in the afternoon
Snowfall expected in the next 24 hours:
0 inches
2 Day Mountain Weather Forecast:

7000 to 8000 Feet
For today, clear and cold. Daytime highs around 30 degrees F. Winds out of the northeast at 20-30 mph decreasing in the afternoon. Gusts to 35 mph. Overnight lows 8-18 degrees F with clear skies. Light winds out of the northeast. Wednesday will be partly cloudy with daytime highs 34-40 degrees F. The winds will be light and start shifting to the west southwest ahead of the storm.

Above 8000 Feet
For today, clear and cold. Daytime highs around 26 degrees F. Winds out of the northeast at 25-35 mph decreasing in the afternoon. Gusts to 45 mph. Overnight lows 13-23 degrees F with clear skies. Light winds out of the northeast. Wednesday will be partly cloudy with daytime highs 30-36 degrees F. The winds will be light and start shifting to the west southwest ahead of the storm.

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