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 Friday, December 15, 2006 at 7:00 am

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Cold wet air is approaching the forecast area, but snow levels have yet to drop across the forecast area this morning. Snow level is currently running around 7,500' and is expected to drop to around 5,500' with cold front passage between 8am and 10am this morning. Moderate westsouthwesterly ridgetop winds persisted overnight and are expected to increase to strong with gusts near 100 mph with cold front passage. Winds are expected to decrease to moderate this afternoon after frontal passage.

The current storm system has brought mostly rain to the forecast area overnight with around 1-2" of new snowfall above 8,000' along the Sierra Crest. Today will be a transition day for the snowpack as cold temperatures begin to refreeze the wet snowpack from the top down. A supportable melt-freeze crust will form at the old/new snow interface later today into the overnight hours. This will begin to add strength to the existing snowpack. It will still take several days for the wet basal layers of the snowpack below 9,000' to fully refreeze. As concerns for wet snow instability decrease, concerns for slab avalanche activity within the new snow will increase later today. As moderate to strong westsouthwesterly ridgetop winds blow throughout the day today and snow level falls, areas of wind loading and subsequent wind slab formation will occur near and above treeline on NW-N-NE-E aspects. Most avalanche activity today is expected to occur from late morning on in response to human triggers. Isolated natural avalanches will become possible later this afternoon and evening in the most heavily wind loaded areas if the upper end of forecast snowfall amounts occur(around 5-7").

Near and above treeline, avalanche danger is MODERATE on wind loaded NW-N-NE-E aspects, 35 degrees and steeper. Pockets of CONSIDERABLE danger could develop late today in this same terrain if the upper end of forecast snowfall amounts occur. Below treeline, avalanche danger is LOW with isolated pockets of MODERATE danger developing this afternoon in steep open areas where strong winds cause isolated areas of wind loading during the day today.

Brandon Schwartz , Avalanche Forecaster

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Today's Central Sierra Weather Observations:
0600 temperature at Sierra Crest (8,700 feet): 30 deg. F
Max. temperature at Sierra Crest past 24 hours: 34 deg. F
Average wind direction at Sierra Crest past 24 hours: westsouthwesterly
Average wind speed at Sierra Crest past 24 hours: 45 mph
Maximum wind gust at Sierra Crest past 24 hours: 68 mph
New snow fall at 8,200 feet past 24 hours: 1 - 2 inches
Total snow depth at 8,200 feet: 14 inches

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Mountain Weather Forecast For Today:
Cloudy skies with snow.
Temperature forecast for 8,000 to 9,000 feet: 26 - 32 deg. F
Ridgetop winds forecast for the Sierra Crest: westsouthwesterly 40 - 60 mph, G 100 mph
Snowfall expected in the next 24 hours: 3 - 7 inches

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2 Day Mountain Weather Forecast:
7000 to 8000 Feet
For today, cloudy skies with rain changing to snow by late morning. Daytime highs of 31 to 39 degrees F. Snow level 7,500' lowering to 5,500'. Snow accumulation 2 to 5 inches. Overnight lows 15 to 20 degrees F with snow showers. Snow level lowering to around 4,000'. Snow accumulation 1 to 3 inches. Saturday will be cloudy with a chance of snow showers. Daytime highs 23 to 31 degrees F. Snow accumulation of 1 to 3 inches.

Above 8000 Feet
For today, cloudy skies with snow. Daytime highs of 26 to 32 degrees F. Snow accumulation 3 to 7 inches. Overnight lows 13 to 18 degrees F. with snow showers. Snow accumulation 1 to 3 inches. Saturday will be cloudy with a chance of snow showers. Snow accumulation 1 to 3 inches. Daytime highs 18 to 26 degrees F. Moderate to strong westsouthwesterly ridgetop winds for today are expected to decrease to light southwesterly overnight into Saturday.

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