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.

Please check out our home page for this year's ski day dates. Starting in December, we will have a drawing at the end of the each month for prizes ranging from bindings to boots courtesy of BCA, NAXO, Garmont, Voile, and others! Everyone who donates $100 or more during the month will be entered into the drawing. Click here to donate. -- SAC Board of Directors

This advisory was posted on December 13, 2008 7:15 AM

A map of the SAC forecast area is available on our home page.

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Today's Advisory:
The avalanche danger is LOW today for all aspects and elevations. Some small, isolated areas of MODERATE danger may exist on east wind protected NW-N-NE slopes steeper than 32 degrees above 7500 ft. where previous snow cover existed and new wind loading occurred.

A strong cold front with a small amount of moisture moved into the forecast area last night. The forecast area only received 1 to 2 inches of snow along the Sierra Crest and about 3 inches in the Mount Rose area overnight. The winds increased as the cold front pushed into the area with sustained ridgetop winds of over 50 mph and gusts that reached 116 mph between midnight and 5 am. As the front moves south and east, snowfall and wind should decrease today. The main effects of this system will be a significant drop in temperatures and a change in the high and dry fall weather pattern. Over the next few days another cold, low pressure system with more moisture should move into the area and bring a better chance for more snow accumulation.

Two avalanche concerns are starting to take shape as the snow and wind continue to impact the forecast area. One: snow accumulating on the weak, faceted surface snow on NW-N-NE aspects above 7500 ft. that were protected from the east winds. In most of these areas today, there should not be enough new snow load to cause widespread failure of this layer. Some small, isolated pockets of instability may result from wind loading in these areas. This weak surface layer cannot handle much new snow load. Avalanches should become increasingly easier to trigger due to failure of this layer as more snow accumulates over the next few days.

The second concern is the wind slabs building on the leeward N-NE-E aspect slopes. These wind slabs will continue to grow over the next few days. As the conditions of the storms change, layers will form in the new snow providing interfaces that these wind slabs could slide on. The east wind scoured surface snow that remained on the northerly aspects near and above treeline prior to this storm could also serve as a sliding surface for the wind slabs. Today there should only be a few small, isolated pockets of instability due to these newly forming wind slabs sitting on the surface facets mentioned above. As the snow increases over the next few days expect these wind loaded areas to become more widespread and more reactive.

The bottom line:

The avalanche danger is LOW today for all aspects and elevations. Some small, isolated areas of MODERATE danger may exist on east wind protected NW-N-NE slopes steeper than 32 degrees above 7500 ft. where previous snow cover existed and new wind loading occurred.

Andy Anderson- Avalanche Forecaster, Tahoe National Forest

Today's Central Sierra Weather Observations:
0600 temperature at Sierra Crest (8,700 feet): 17 deg. F.
Max. temperature at Sierra Crest past 24 hours: 45 deg. F.
Average wind direction at Sierra Crest past 24 hours: Southwest to West Southwest
Average wind speed at Sierra Crest past 24 hours: 40 mph
Maximum wind gust at Sierra Crest past 24 hours: 116 mph
New snowfall at 8,200 feet past 24 hours: 1 - 2 inches
Total snow depth at 8,200 feet: 11 inches
Mountain Weather Forecast For Today:
Snow in the morning becoming scattered by this afternoon. Winds and temperatures decreasing significantly throughout the day.
Temperature forecast for 8,000 to 9,000 feet: 14-21 deg. F
Ridgetop winds forecast for the Sierra Crest: 45-65 mph with gusts to 120 mph in the morning decreasing to 35-45 mph with gusts to 85 this afternoon.
Snowfall expected in the next 24 hours: 2-6 inches
2 Day Mountain Weather Forecast:

7000 to 8000 Feet:

Today, snow showers in the morning becoming scattered this afternoon with accumulations of 2 to 4 inches Daytime highs 19 to 24 deg. F. Winds out of the west at 25 to 35 mph with gusts to 50 mph this morning decreasing to 15 to 25 mph with gusts to 35 mph by this afternoon.

Tonight, cloudy with scattered snow showers with up to 2 inches of accumulation. Overnight lows 7 to 11 deg. F. Winds out of the west at 10 to 20 mph with gusts to 30 mph.

For tomorrow, snow with 1 to 3 inches of accumulation. Daytime highs 15 to 22 deg. F. Winds out of the southwest at 10 to 20 mph with gusts to 30 mph.

Above 8000 Feet:

Today, numerous snow showers in the morning becoming more scattered this afternoon with accumulations of 2 to 4 inches Daytime highs 14 to 21 deg. F. Winds out of the west at 45 to 65 mph with gusts to 120 mph this morning decreasing to 35 to 45 mph with gusts to 85 mph by this afternoon.

Tonight, cloudy with scattered snow showers with up to 2 inches of accumulation. Overnight lows 0 to 7 deg. F. Winds out of the west at 20 to 30 mph with gusts to 50 mph.

For tomorrow, snow with 2 to 4 inches of accumulation. Daytime highs 10 to 15 deg. F. Winds out of the southwest at 15 to 25 mph with gusts to 45 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:
	Saturday:	Saturday Night:	Sunday:
Weather:
Temperatures:	deg. F.	deg. F.	deg. F.
Wind direction:
Wind speed:
Expected snowfall:	O in.	O in.	O in.
For 8000-9000 ft:
	Saturday:	Saturday Night:	Sunday:
Weather:
Temperatures:	deg. F.	deg. F.	deg. F.
Wind direction:
Wind speed:
Expected snowfall:	O in.	O in.	O in.