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 February 1, 2008 6:56 AM
Click here for a detailed map of the SAC forecast area

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Today's Advisory:

Near and above treeline, avalanche danger is MODERATE with pockets of CONSIDERABLE danger in wind loaded areas on N-NE-E aspects, 35 degrees and steeper. Below treeline, avalanche danger is LOW with pockets of MODERATE danger in wind loaded areas, 37 degrees and steeper.

The most recent storm system that affected the forecast area during the past 24 hours has moved off to the east. Snow showers and moderate ridgetop winds remain over the forecast area this morning. A period of sunshine is expected mid day. Ski area snow study plots and remote sensors are reporting new snow accumulation over the past 24 hours ranging from 8 to 15 inches along the Sierra Crest from Yuba Pass to Carson Pass and 4 to 6 inches from Ebbets Pass southward. In the Mount Rose area, 6 to 8 inches of new snow has been reported. A new snow density of 17% was reported from the snow study plot at Sugar Bowl ski area this morning. Southwest to west ridgetop winds are expected to maintain moderate speed today ahead of the next storm system which is expected to affect the area on Saturday.

Yesterday, strong southwest ridgetop winds transported new snow, causing dense slab formation in wind loaded areas. On Mt. Judah (Donner Summit area), small natural avalanches were observed secondary to natural cornice collapse on NE-E aspects above treeline. Shooting cracks and were observed just below the top of the ridge on a heavily wind loaded east aspect. Slab formation in this area was around 2 feet deep and exhibited greater density than the recent new snow layer below it. Near treeline, small pockets of shallow surface slabs up to 4 inches deep were skier triggered in wind affected areas on NW aspects while very similar instability was observed below treeline on east aspects in the area. In Munchkins (Outside Alpine Meadows ski area boundary), a skier triggered avalanche was reported near treeline on a wind loaded, 35 degree east aspect in an open area at 7,000'. A shooting crack from the ski tip opened into a propagating fracture with slab failure 1.5 feet deep. The avalanche measured 150 feet wide and ran 450 feet down slope. The bed surface was reported more dense than the slab in this area.

Today, westerly ridgetop winds will cause some areas of continued wind loading near and above treeline on N-NE-E aspects. The high density slabs that formed yesterday in near and above treeline areas may be difficult to trigger today, but hold significant destructive potential if set into motion. Isolated natural avalanches remain possible while human triggered avalanches are probable in steep wind loaded areas on NW-N-NE-E aspects. Below treeline, small areas of human triggered avalanches are possible in wind affected areas while natural avalanche activity is unlikely. The majority of snowpack instability that occurs today is expected north of Ebbets Pass.

The bottom line: Near and above treeline, avalanche danger is MODERATE with pockets of CONSIDERABLE danger in wind loaded areas on N-NE-E aspects, 35 degrees and steeper. Below treeline, avalanche danger is LOW with pockets of MODERATE danger in wind loaded areas, 37 degrees and steeper

Please send us your snow, weather, and avalanche observations by clicking the submit observations link on our contact page.

Brandon Schwartz, Avalanche Forecaster

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: 20 deg. F
Average wind direction at Sierra Crest past 24 hours: Southwest
Average wind speed at Sierra Crest past 24 hours: 62 mph
Maximum wind gust at Sierra Crest past 24 hours: 116 mph
New snow fall at 8,200 feet past 24 hours: 4 to 15 inches
Total snow depth at 8,200 feet: 87 to 97 inches

Mountain Weather Forecast For Today:
Cloudy with scatted snow showers, sun breaks during mid day.
Temperature forecast for 8,000 to 9,000 feet: 19 to 27 deg. F
Ridgetop winds forecast for the Sierra Crest: West at 25 to 40 mph with gusts to 65 mph, decreasing to 15 to 25 mph with gusts to 40 mph in the afternoon.
Snowfall expected in the next 24 hours: 0 to 1 inch

2 Day Mountain Weather Forecast:

7000 to 8000 Feet:
Today, mostly cloudy with scatted snow showers. Sun breaks during mid day. Daytime highs 24 to 31 deg. F. West winds at 15 to 20 mph with gusts to 35 mph.

Tonight, mostly cloudy with isolated snow showers after midnight. Overnight lows 14 to 20 deg. F. West winds at 10 to 20 mph, decreasing to 5 to 15 mph after midnight.

For Saturday, cloudy with a chance of snow in the morning. Snow likely in the afternoon. Snow accumulation up to 4 inches. Daytime highs 26 to 32 deg. F. Southwest winds at 15 to 25 mph with gusts to 35 mph.

Above 8000 Feet:
Today, mostly cloudy with scatted snow showers. Sun breaks during mid day. Daytime highs 19 to 27 deg. F. West winds at 20 to 30 mph with gusts to 65 mph, decreasing to 15 to 25 mph with gusts to 40 mph in the afternoon.

Tonight, mostly cloudy with isolated snow showers after midnight. Overnight lows 13 to 19 deg. F. West winds at 15 to 25 mph, decreasing to 10 to 20 mph after midnight.

For Saturday, cloudy with a chance of snow in the morning. Snow likely in the afternoon. Snow accumulation up to 4 inches. Daytime highs 22 to 28 deg. F. Southwest winds at 20 to 30 mph with gusts to 40 mph. Wind gusts increasing to 60 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:
	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.