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 10, 2008 7:00 AM
Click here for a detailed map of the SAC forecast area

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Today's Advisory:

This morning, avalanche danger is LOW for all elevations and aspects. Areas of MODERATE avalanche danger will quickly develop at all elevations on SE-S-SW-W aspects, 37 degrees and steeper in response to daytime warming.

Overnight the air temperatures along the Sierra Crest and in the Mount Rose area remained above freezing. Warm temperatures and sunny skies will continue across the forecast area due to the strong high pressure ridge that remains in place. A low pressure system passing through the Pacific Northwest should bring a few mid to high level clouds to the forecast area today and tonight. It should also cause the winds to shift more to the west today. Tomorrow the winds should shift back to the north and decrease again.

Even though the nighttime lows did not fall below freezing, mostly clear skies should have allowed the snow surfaces that melted yesterday to refreeze due to radiational cooling. This refreeze will not be as thorough as the refreezes that occurred earlier this week. The snow surface shouldsoften quickly on any sun exposed aspects today. During melt-freeze cycles the snowpack alternates between getting weaker during the melting phase as free water dissolves bonds within layers and between layers and getting stronger during the freezing phase as the water turns to ice and cements those wet layers in place. Until today the freezing phase of this melt-freeze cycle has been longer than the melting phase limiting the free water to the upper 4 to 6 inches of the snowpack. Today melting conditions should occur deeper in the snowpack due to a less robust overnight refreeze, continued sun, and warm air temperatures.

Snowpit data and layer bonding tests performed over the past several days in the Donner Summit, Mount Rose, Carson Pass, Deep Creek, and Ebbets Pass areas all show continued settlement and strong layer bonding of a cold snowpack on northerly aspects. Southerly aspects show well bonded and strong snow below the top 4 to 6 inches that has repeatedly become wet and weak during the melting phase of the current melt-freeze cycle. As melt water percolates deeper into the snowpack some of these stronger lower layers could serve as boundaries where water concentrates and completely dissolves the bonds in that layer providing a weak layer and sliding surface for wet snow avalanches.

Today, northerly aspects will continue to hold cold and unconsolidated surface snow and southerly aspects will have melt-freeze / corn conditions. As daytime warming occurs, human triggered wet snow avalanches will become possible on steep sun exposed SE-S-SW-W aspects. Gradual warming over the past several days has allowed the snowpack to adjust to rising air temperatures. As a result, natural avalanche activity is an unlikely today.
The bottom line: This morning, avalanche danger is LOW for all elevations and aspects. Areas of MODERATE avalanche danger will quickly develop at all elevations on SE-S-SW-W aspects, 37 degrees and steeper in response to daytime warming.

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): 34 deg. F
Max. temperature at Sierra Crest past 24 hours: 47 deg. F.
Average wind direction at Sierra Crest past 24 hours: Northeast shifting to the west
Average wind speed at Sierra Crest past 24 hours: 12 mph
Maximum wind gust at Sierra Crest past 24 hours: 23 mph
New snow fall at 8,200 feet past 24 hours: 0 inches
Total snow depth at 8,200 feet: 87 inches
Mountain Weather Forecast For Today:
Partly cloudy and warm.
Temperature forecast for 8,000 to 9,000 feet: around 43 deg. F
Ridgetop winds forecast for the Sierra Crest: West at 10 to 15 mph with gusts to 25 mph.
Snowfall expected in the next 24 hours: 0 inches
2 Day Mountain Weather Forecast:

7000 to 8000 Feet:
Today, partly cloudy with daytime highs around 47 deg. F. Light winds becoming west around 10 mph in the afternoon.

Tonight, partly cloudy skies with overnight lows 20 to 28 deg. F. West winds at 10 to 15 mph.

For Monday, sunny skies with daytime highs around 46 deg. F. Northeast winds at 10 to 15 mph.

Above 8000 Feet:
Today, partly cloudy with daytime highs around 43 deg. F. West winds at 10 to 15 mph with gusts to 25 mph.

Tonight, partly cloudy skies with overnight lows 22 to 30 deg. F. West winds at 10 to 20 mph with gusts to 30 mph.

For Monday, sunny skies with daytime highs around 44 deg. F. North winds at 10 to 15 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:
	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.