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 17, 2008 7:00 AM

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

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Today's Advisory:
Near and above treeline, avalanche danger is MODERATE on wind loaded NW-W-SW-S-SE aspects, 37 degrees and steeper with isolated pockets of CONSIDERABLE on the most heavily wind loaded, sun exposed slopes. Steep cross loaded NW and SE facing gullies will be the most suspect. Below treeline, avalanche danger is MODERATE in open, sun exposed areas 40 degrees and steeper.

Strong east and northeasterly winds have been scouring the N-NE-E facing slopes since Saturday night. These winds should continue this morning as a high pressure ridge starts to build over the forecast area. This ridge should bring clearer skies, warmer temperatures and lighter winds to the forecast area through Tuesday. Today the forecast calls for temperatures to jump 10 to 15 degrees F. at all elevations. The winds should also start to decrease and shift more to the west.

The cold, light new snow that fell last Thursday night and Friday provided ample material for the strong N-NE-E winds to transport onto NW-W-SW-S-SE slopes. This snow became more cohesive due to the wind transport and has formed soft slabs on these aspects. In many places previous scouring and melting on the W-SW-S aspects has exposed bare ground and therefore these shallow soft slabs have no bed surface for avalanches resulting from their failure to run on. Higher elevation slopes that had more snow, lower elevation protected slopes, cross-loaded gullies or any other areas that still had extensive snow cover on these aspects prior to Thursday's storm will be more suspect. Over the last 36 hours the wind will have deposited new wind slabs on top of a hard, refrozen crust on these slopes. Yesterday observers reported soft slabs that cracked with a skier's weight and some tender cornice formation in the Mt. Rose area, the Carson Pass area, and in the Silver Peak area on these aspects.

These soft slabs will be even more of a concern today because the winds have formed them on the slopes that will be most affected by the rapid increase in temperature and strong March sun. This sudden change will be hard for the cold new snow to adjust to and will cause more instability and weakness to form in the snowpack. Human triggered avalanches will be possible on steep, sun exposed slopes where new snow sits on top of a hard old snow surface. Natural activity could become possible on heavily wind loaded, steep, sun exposed slopes that had previous snow cover especially in steep cross loaded gullies. Most avalanche activity should start out as pinwheels and point release slides but could progress to slab avalanches as the day warms up. These instabilities should not form on the N-NE-E aspects near and above treeline due to heavy scouring of the snow surface, colder temperatures, and less sun exposure.

The bottom line: Near and above treeline, avalanche danger is MODERATE on wind loaded NW-W-SW-S-SE aspects, 37 degrees and steeper with isolated pockets of CONSIDERABLE on the most heavily wind loaded, sun exposed slopes. Steep cross loaded NW and SE facing gullies will be the most suspect. Below treeline, avalanche danger is MODERATE in open, sun exposed areas 40 degrees and steeper.
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): 13 deg. F
Max. temperature at Sierra Crest past 24 hours: 24 deg. F.
Average wind direction at Sierra Crest past 24 hours: Northeast
Average wind speed at Sierra Crest past 24 hours: 45 mph.
Maximum wind gust at Sierra Crest past 24 hours: 82 mph
New snowfall at 8,200 feet past 24 hours: 0 inches
Total snow depth at 8,200 feet: 89 inches
Mountain Weather Forecast For Today:
Sunny this morning and becoming partly cloudy this afternoon.
Temperature forecast for 8,000 to 9,000 feet: 30 to 36 deg. F
Ridgetop winds forecast for the Sierra Crest: East at 20 to 35 mph with gusts to 65 mph.
Snowfall expected in the next 24 hours: 0 inches
2 Day Mountain Weather Forecast:

7000 to 8000 Feet:
Today, sunny skies this morning becoming partly cloudy this afternoon. Daytime highs 31 to 42 deg. F. Southeast winds at 10 to 15 mph shifting to the north in the afternoon.

Tonight, partly cloudy skies with overnight lows around 23 deg. F. Northwest winds at 10 mph.

For Tuesday, partly cloudy skies with daytime highs 42 to 50 deg. F. West winds at 10 to 15 mph.

Above 8000 Feet:
Today, sunny skies this morning becoming partly cloudy this afternoon. Daytime highs 30 to 36 deg. F. East winds at 20 to 35 mph with gusts to 65 mph this morning then shifting to the north and decreasing to 15 to 20 mph with gusts to 35 mph in the afternoon.

Tonight, partly cloudy skies with overnight lows around 26 deg. F. Northwest winds at 10 to 15 mph.

For Tuesday, partly cloudy skies with daytime highs 36 to 42 deg. F. West 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.