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 9, 2008 6:46 AM
Click here for a detailed map of the SAC forecast area

2_moderate
Today's Advisory:

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

High pressure is firmly in place over the forecast area. Remote sensors are indicating that an air temperature inversion is affecting the northern half of the forecast area this morning. Warmer air has been reported along the ridges and colder air reported down at the valley floors and in the Lake Tahoe Basin. Air temperatures are expected to warm to above freezing again today at all elevations. Ridgetop winds have remained light from the northeast for the past 24 hours. Winds are expected to shift to the west and remain light today.

Yesterday, warming daytime air temperatures again created localized areas of wet snow instability in the form of roller balls on SE-S-SW aspects. The top 4 to 6 inches of the snowpack on southerly aspects started melting and became wet by mid morning. Northerly aspects above 7,000' have yet to undergo melt-freeze conditions, still holding on to a cold snowpack. The recent storm snow continues to show increasing layer bond strength on all aspects. Snowpit data and layer bonding tests performed over the past several days in the Donner Summit, Mount Rose, Carson Pass, and Ebbets Pass areas all show continued settlement and strong layer bonding of a cold snowpack on northerly aspects. Southerly aspects are showing well bonded and strong snow below the top 4 to 6 inches that has repeatedly become wet and weak during the daytime warming phase of the on going melt-freeze cycle.

Below freezing air temperatures in the southern portion of the forecast area and radiational cooling under clear skies in the northern portion of the area has allowed surface snow that melted yesterday to refreeze overnight. Today, northerly aspects will continue to hold cold and unconsolidated surface snow that is well bonded to the snowpack layers below. As daytime warming occurs, human triggered avalanches involving the top several inches of wet surface snow will become possible on steep sun exposed SE-S-SW 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 event today. Any avalanche activity that does occur is expected in response to human triggering.

The bottom line: This morning, avalanche danger is LOW for all elevations and aspects. Areas of MODERATE avalanche danger will develop at all elevations on SE-S-SW 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.

Brandon Schwartz, Avalanche Forecaster

Today's Central Sierra Weather Observations:
0600 temperature at Sierra Crest (8,700 feet): 26 deg. F
Max. temperature at Sierra Crest past 24 hours: 36 to 45 deg. F, warmest in the south
Average wind direction at Sierra Crest past 24 hours: Northeast
Average wind speed at Sierra Crest past 24 hours: 18 mph
Maximum wind gust at Sierra Crest past 24 hours: 40 mph
New snow fall at 8,200 feet past 24 hours: 0 inches
Total snow depth at 8,200 feet: 88 inches

Mountain Weather Forecast For Today:
Sunny skies with warming air temperatures.
Temperature forecast for 8,000 to 9,000 feet: 39 to 44 deg. F
Ridgetop winds forecast for the Sierra Crest: West at 10 to 20 mph.
Snowfall expected in the next 24 hours: 0 inches

2 Day Mountain Weather Forecast:

7000 to 8000 Feet:
Today, sunny skies with daytime highs 39 to 45 deg. F. Light winds becoming southwest around 10 mph in the afternoon.

Tonight, partly cloudy skies in the evening, then becoming mostly cloudy. Overnight lows 20 to 28 deg. F. Southwest winds up to 10 mph.

For Sunday, mostly cloudy skies with daytime highs around 46 deg. F. Light winds becoming west around 10 mph in the afternoon.

Above 8000 Feet:
Today, sunny skies with daytime highs around 42 deg. F. West winds at 10 to 15 mph.

Tonight, partly cloudy skies in the evening, then becoming mostly cloudy. Overnight lows 23 to 29 deg. F. West winds at 10 to 20 mph.

For Sunday, mostly cloudy skies with daytime highs around 41 deg. F. West winds at 10 to 20 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:
	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.