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 4, 2008 7:00 AM
Click here for a detailed map of the SAC forecast area

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Today's Advisory:

Near and above treeline the avalanche danger is MODERATE on recently wind loaded slopes 37 degrees and steeper. Below treeline the avalanche danger is LOW with pockets of MODERATE danger in open areas, 37 degrees and steeper.

The storm has moved east of the forecast area leaving clear skies, cold temperatures, and strong north and east winds in its wake. The cold air temperatures and northerly flow could cause some isolated snow showers south of Lake Tahoe this morning; however, these should be short lived and not produce much accumulation. A high pressure ridge should start to build over the forecast area causing the north and east winds to moderate and the temperatures to slowly climb over the next few days.

Only 1 to 3 inches of new snow accumulated yesterday as the storm quickly moved off to the east. A decrease in wind accompanied this decrease in snow fall rates. This combination allowed the new snow to start to settle and consolidate, which began to strengthen some of the storm snow weaknesses. As a result, most of the natural avalanche activity that occurred yesterday happened early in the day. Human triggerable avalanche activity continued to exist through the day. In the Mount Rose area a skier triggered avalanche (see photos) occurred on a steep north facing couloir. By mid afternoon enough bonding in the new snow had occurred so that only north facing test slopes steeper than 40 degrees showed signs of human triggerable instability. This strengthening trend should have continued overnight. Also the north and east winds should start to scour some of the areas that were wind loaded during the storm reducing the weight of the slab on these slopes. These factors will result in a decrease in the avalanche danger today.

The north through east winds will still transport snow today and should deposit new wind slabs onto leeward slopes today. The main wind loaded areas will be the W-SW-S aspects. The snowpack on these aspects should be in good shape to adjust to the new load due to scouring during the storm. Also, the wind slabs deposited today should be much smaller than anything created during the storm. NW and SE cross loaded slopes will be more of an issue since they also received loading during the storm. Look for ripples, drifts, cornices, and blowing snow to help determine which slopes are loaded. While natural activity is unlikely today human triggered avalanche activity is still possible on steep, leeward slopes where wind loading occurs. Any avalanche activity that does occur today should be occur in the new snow above the old/new snow interface.
The bottom line: Near and above treeline, avalanche danger is MODERATE on recently wind loaded slopes 37 degrees and steeper. Below treeline, avalanche danger is LOW with pockets of MODERATE danger in open areas, 37 degrees and steeper.

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

Andy Anderson, Avalanche Forecaster

Today's Central Sierra Weather Observations:
0600 temperature at Sierra Crest (8,700 feet): 7 deg. F
Max. temperature at Sierra Crest past 24 hours: 19 deg. F
Average wind direction at Sierra Crest past 24 hours: Southwest shifting to the northeast after 10 pm yesterday.
Average wind speed at Sierra Crest past 24 hours: 45 mph while the wind was from the southwest and 25 mph after it shifted to the northeast
Maximum wind gust at Sierra Crest past 24 hours: 110 mph
New snow fall at 8,200 feet past 24 hours: 1 to 3 inches
Total snow depth at 8,200 feet: 100 inches
Mountain Weather Forecast For Today:
Mostly sunny with some isolated snow showers this morning south of Lake Tahoe.
Temperature forecast for 8,000 to 9,000 feet: 12 to 17 deg. F
Ridgetop winds forecast for the Sierra Crest: Northeast at 20 to 35 mph with gusts from 45 to 60 mph.
Snowfall expected in the next 24 hours: 0 inches north of Lake Tahoe and around 1 inch south of Lake Tahoe.
2 Day Mountain Weather Forecast:

7000 to 8000 Feet:
Today, mostly sunny with isolated snow showers south of Lake Tahoe this morning producing little accumulation. Daytime highs 15 to 22 deg. F. Northeast winds at 10 to 20 mph with gusts from 30 to 40 mph.

Tonight, mostly clear with overnight lows 7 to 13 deg. F. East winds at 10 to 15 mph with gusts to 25 mph.

For Tuesday, mostly sunny in the morning with clouds increasing during the day. Daytime highs 32 to 36 deg. F. East winds at 5 to 10 mph.

Above 8000 Feet:
Today, mostly sunny with isolated snow showers south of Lake Tahoe this morning producing little accumulation. Daytime highs 12 to 17 deg. F. Northeast winds at 20 to 35 mph with gusts from 45 to 60 mph.

Tonight, mostly clear with overnight lows 6 to 12 deg. F. Northeast winds at 20 to 35 mph with gusts to 60 mph decreasing to 15 to 25 mph with gusts to 45 after midnight.

For Tuesday, mostly sunny in the morning with clouds increasing during the day. Daytime highs 28 to 34 deg. F. North winds at 10 to 15 mph with gusts to 25 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:
	Monday:	Monday Night:	Tuesday:
Weather:
Temperatures:	deg. F.	deg. F.	deg. F.
Wind direction:
Wind speed:
Expected snowfall:	O in.	O in.	O in.
For 8000-9000 ft:
	Monday:	Monday Night:	Tuesday:
Weather:
Temperatures:	deg. F.	deg. F.	deg. F.
Wind direction:
Wind speed:
Expected snowfall:	O in.	O in.	O in.