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 Saturday, December 16, 2006 at 6:59 am

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Cold dry air descended upon the forecast area yesterday afternoon and through the overnight hours. Ridgetop winds have eased to moderate and shifted to easterly overnight. The remnants of yesterday's storm will continue to create snow showers over the southern half of the forecast area today. High pressure will build into the forecast area over the next several days and air temperatures will remain cold.

Storm totals are running around 2-5" across the forecast area this morning. Areas of shallow wind slab were created yesterday in wind loaded areas above treeline on NW-N-NE-E aspects. So far, these slabs have shown minimal instability in response to human triggers. Continued snowfall during the day today will allow snowpack instability to linger on recently wind loaded areas near and above treeline. Moderate east to northeast winds this morning are expected to strip snow from NE-E aspect start zones and continue to wind load on NW-N aspect avalanche start zones. Winds are expected to become light by late morning.

Snowpack conditions vary throughout the forecast area following the recent warm weather and rain up to 9,000'. Along the Sierra Crest, the snowpack below 8,500' became very wet from top to bottom and is now in a process of refreezing from the top down and becoming very strong. Above 8,500', only the upper half of the snowpack was affected by rain. Basal layer facets and near crust facets remain in the lower half of the snowpack and continue to show failure in response to moderate force during stability tests.

In the Mount Rose area, the snowpack above 9,000' remains very cold and faceted with well developed depth hoar at the bottom of the snowpack on NW-N-NE aspects. Stability tests performed yesterday consistently created failure on this depth hoar layer in response to easy to moderate force. As the thin melt-freeze crust at the old/storm snow interface gains strength, less force will be exerted by skiers and snowmobiles on the depth hoar layer. Despite the strength gain of the near surface crust, basal layer failure remains a concern, especially with cold air temperatures over the next several days.

North of Hwy 50

Near and above treeline, avalanche danger is LOW with isolated pockets of MODERATE danger on wind loaded NW-N aspects, 35 degrees and steeper. Below treeline, avalanche danger is LOW.

South of Hwy 50

Near and above treeline, avalanche danger is MODERATE on wind loaded NW-N aspects, 35 degrees and steeper. Below treeline, avalanche danger is LOW.

Brandon Schwartz , Avalanche Forecaster

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Today's Central Sierra Weather Observations:
0600 temperature at Sierra Crest (8,700 feet): 12 deg. F
Max. temperature at Sierra Crest past 24 hours: 29 deg. F
Average wind direction at Sierra Crest past 24 hours: westsouthwesterly shifting to easterly
Average wind speed at Sierra Crest past 24 hours: 45 mph
Maximum wind gust at Sierra Crest past 24 hours: 101 mph
New snow fall at 8,200 feet past 24 hours: 2 - 5 inches
Total snow depth at 8,200 feet: 20 inches

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Mountain Weather Forecast For Today:
Partly cloudy skies by afternoon with snow showers in the southern half of the forecast area.
Temperature forecast for 8,000 to 9,000 feet: 13 - 18 deg. F
Ridgetop winds forecast for the Sierra Crest: northeasterly 10 - 20 mph, G 25 mph
Snowfall expected in the next 24 hours: 2 - 4 inches mainly south of Hwy 50

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2 Day Mountain Weather Forecast:
7000 to 8000 Feet
For today, partly to mostly cloudy skies with snow showers south of Hwy 50. Daytime highs of 20 to 25 degrees F. Snow accumulation 1 to 2 inches. Overnight lows 10 to 15 degrees F with partial clearing. Sunday will be partly cloudy with daytime highs 18 to 23 degrees F.

Above 8000 Feet
For today, partly to mostly cloudy skies with snow showers south of Hwy 50. Daytime highs of 13 to 18 degrees F. Snow accumulation 2 to 4 inches. Overnight lows 5 to 10 degrees F. Sunday will be partly cloudy with daytime highs 12 to 17 degrees F. Light northeasterly ridgetop winds for today are expected to increase to moderate northeasterly on Sunday.

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.