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 March 13, 2008 7:00 AM

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

2_moderate
Today's Advisory:

The avalanche danger is LOW above 8500 ft. Below 8500 ft. the avalanche danger is MODERATE on all aspects on slopes steeper than 37 degrees that receive rain today. The NW-N-NE slopes that have not experienced as much melting and refreezing will be the most suspect.

Remote sensors indicate that the snow level is currently around 8000 ft. The snow level should remain above 7000 ft and could be as high as 8500 ft. for most of the day before dropping to lake level overnight as a cold front moves into the area. Showers and high winds preceding this front moved into the area overnight. They should start to taper off this afternoon before another series of storms impacts the forecast area over the next few days. These storms should bring 6 to 12 inches of snow, much colder temperatures, and moderate to strong southwest winds.

Snowpack observations from across the forecast area continue to show a strong, consolidated snowpack. The snow surface did melt some yesterday as the sun came out in the afternoon. Overnight air temperatures near or below freezing allowed snow that melted during the day yesterday to refreeze and gain strength. As rain falls on this snow surface today it should soften again before the rain changes to snow later today and tonight. This warm surface should bond well to the new snow when it refreezes tonight. Until then the rain will add more weight to and take strength away from the snowpack on all aspects by introducing free water, warmth, and lubrication. This free water and warmth will melt some of the bonds holding the snowpack together and make it weaker. On the southerly aspects channels that drain free water through the snowpack have formed due to the prolonged melt/freeze cycle. These channels will also help to drain the rain water through the snowpack and should keep instability from becoming large and widespread on these aspects. On the northerly aspects that have not experienced much melting and refreezing this rain water will be more likely to saturate layers and cause the snowpack to weaken enough for avalanche activity to occur. Above the freezing level only a 2 to 3 inches of new snow has fallen and should not be enough to form a reactive slab layer.

Today, human triggerable avalanches could become possible on steep slopes below the freezing level due to rain on snow. Small precipitation amounts, a prolonged melt/freeze cycle, and a well consolidated snowpack should cause natural avalanche activity to remain unlikely. These instabilities should become more isolated as the weather cools and the snowpack refreezes tonight. Wind and more snow will start to form slabs over the next few days will cause the avalanche danger to increase over the next few days.

The bottom line: The avalanche danger is LOW above 8500 ft. Below 8500 ft. the avalanche danger is MODERATE on all aspects on slopes steeper than 37 degrees that receive rain today. The NW-N-NE slopes that have not experienced as much melting and refreezing will be the most suspect.
Public donations to the avalanche center this season are below our fundraising goal. We are going to raffle a beacon, shovel, probe, and backpack package as a way give back to those who donate $100 or more before March 30th. For more information on the raffle and amount of donations received click here.

Andy Anderson, Avalanche Forecaster

Today's Central Sierra Weather Observations:
0600 temperature at Sierra Crest (8,700 feet): 29 deg. F
Max. temperature at Sierra Crest past 24 hours: 43 deg. F.
Average wind direction at Sierra Crest past 24 hours: Southwest
Average wind speed at Sierra Crest past 24 hours: 38 mph.
Maximum wind gust at Sierra Crest past 24 hours: 78 mph
New snowfall at 8,200 feet past 24 hours: 2 inches
Total snow depth at 8,200 feet: 81 inches
Mountain Weather Forecast For Today:
Mostly cloudy with scattered snow showers.
Temperature forecast for 8,000 to 9,000 feet: 28 to 34 deg. F
Ridgetop winds forecast for the Sierra Crest: Southwest at 25 to 40 mph with gusts to 70 mph.
Snowfall expected in the next 24 hours: 3 inches
2 Day Mountain Weather Forecast:

7000 to 8000 Feet:
Today, mostly cloudy with scattered snow showers and accumulations up to 1 inch. Daytime highs 34 to 44 deg. F. Southwest winds at 20 to 30 mph with gusts to 45 mph.

Tonight, mostly cloudy with scattered snow showers. Overnight lows 17 to 22 deg. F. Southwest winds at 15 to 25 mph with gusts to 40 mph decreasing to 10 to 20 mph with gusts to 30 mph after midnight.

For Friday, mostly cloudy skies with a chance of snow. Accumulations of up to 3 inches. Daytime highs 24 to 31 deg. F. Southwest winds at 15 to 25 mph with gusts to 40 mph.

Above 8000 Feet:
Today, mostly cloudy with scattered snow showers and accumulations up to 2 inches. Daytime highs 28 to 34 deg. F. Southwest winds at 25 to 40 mph with gusts to 70 mph.

Tonight, mostly cloudy with scattered snow showers. Overnight lows around 16 deg. F. West winds at 20 to 35 mph with gusts to 60 mph.

For Friday, mostly cloudy skies with a chance of snow. Accumulations of up to 3 inches. Daytime highs 21 to 26 deg. F. Southwest winds at 20 to 30 mph with gusts to 45 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:
	Thursday:	Thursday Night:	Friday:
Weather:
Temperatures:	deg. F.	deg. F.	deg. F.
Wind direction:
Wind speed:
Expected snowfall:	O in.	O in.	O in.
For 8000-9000 ft:
	Thursday:	Thursday Night:	Friday:
Weather:
Temperatures:	deg. F.	deg. F.	deg. F.
Wind direction:
Wind speed:
Expected snowfall:	O in.	O in.	O in.