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 December 14, 2008 6:48 AM

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

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Today's Advisory:
Near and above treeline, avalanche danger is MODERATE on NW-N-NE-E aspects, 35 degrees and steeper. Below treeline, avalanche danger is LOW with pockets of MODERATE danger on NW-N-NE aspects above 7,500' that are 32 degrees and steeper.

The current storm system is picking up increasing moisture off of the Pacific Ocean and it is combining with an Arctic air mass. Moderate snowfall rates are expected to continue this morning and intensify this afternoon and overnight. Single digit air temperatures on the mountain tops this morning are expected to rise into the low teens today. Ridgetop winds have decreased from 24 hours ago, but remain moderate in speed out of the west southwest. Storm totals are running 6 to 10 inches across the forecast area.

Avalanche concern number one: Near and above treeline, fresh slabs have formed in wind loaded areas below ridgelines. Expect slopes above 7,500' with a northerly aspect component to have an old snow crust below the new snow or slab. Expect other areas will have new snow over the ground (dirt). As wind loading continues, mainly on NW-N-NE-E aspects, expect continued formation of unstable slabs in lee areas. Small but not inconsequential human triggered avalanches are possible. Natural avalanches are unlikely but not impossible today.

Avalanche concern number two: Near and below treeline new snow sits on top of a weak layer of well developed faceted snow crystals in some areas. This weak layer is the remnants of the 11/26 snowfall that has now become a buried weak layer at the bottom of the new snow. This weak layer exists above 7,500' on east wind protected NW-N-NE aspects in near and below treeline areas. Unstable snow is expected in areas where this faceted snow layer exists as it will handle new snow loading poorly, even on lower angle slopes.

The bottom line:

Near and above treeline, avalanche danger is MODERATE on NW-N-NE-E aspects, 35 degrees and steeper. Below treeline, avalanche danger is LOW with pockets of MODERATE danger on NW-N-NE aspects above 7,500' that are 32 degrees and steeper.

Please share your backcountry observations with us, especially if you see or trigger an avalanche. To report an observation click here.

Brandon Schwartz - Avalanche Forecaster, Tahoe National Forest

Today's Central Sierra Weather Observations:
0600 temperature at Sierra Crest (8,700 feet): 8 deg. F.
Max. temperature at Sierra Crest past 24 hours: 10 deg. F.
Average wind direction at Sierra Crest past 24 hours: West Southwest
Average wind speed at Sierra Crest past 24 hours: 26 mph
Maximum wind gust at Sierra Crest past 24 hours: 56 mph
New snowfall at 8,200 feet past 24 hours: 4 to 6 inches
Total snow depth at 8,200 feet: 6 to 24 inches

Mountain Weather Forecast For Today:
Scattered snow showers in the morning, increasing as the day progresses.
Temperature forecast for 8,000 to 9,000 feet: 10 to 15 deg. F
Ridgetop winds forecast for the Sierra Crest: Southwest winds at 20 to 30 mph with gusts to 50 mph in the afternoon.
Snowfall expected in the next 24 hours: 8 to 16 inches

2 Day Mountain Weather Forecast:

7000 to 8000 Feet:

Today, cloudy with scattered snow showers in the morning then numerous snow showers in the afternoon. Snow accumulation up to 4 inches. Daytime highs 15 to 22 deg. F. Southwest winds at 15 to 20 mph with gusts to 30 mph.

Tonight, cloudy with snow. Snow accumulation 6 to 12 inches. Overnight lows 10 to 15 deg. F. Southwest winds at 15 to 25 mph with gusts to 40 mph.

Tomorrow, cloudy with snow. Snow accumulation 6 to 12 inches. Daytime highs 14 to 19 deg. F. Southwest winds at 15 to 25 mph.

Above 8000 Feet:

Today, cloudy with scattered snow showers in the morning then numerous snow showers in the afternoon. Snow accumulation up to 4 inches. Daytime highs 10 to 15 deg. F. Southwest winds at 20 to 30 mph with gusts to 50 mph in the afternoon.

Tonight, cloudy with snow. Snow accumulation 6 to 12 inches. Overnight lows 6 to 10 deg. F. Southwest winds at 30 to 45 mph with gusts to 75 mph.
Tomorrow, cloudy with snow. Snow accumulation 6 to 12 inches. Daytime highs 11 to 16 deg. F. Southwest winds at 25 to 35 mph with gusts to 65 mph, decreasing to 55 mph in the afternoon.

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