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 Thursday, March 1st, 2007 at 6:30 am

The bottom line: Avalanche danger near and above treeline is MODERATE with the greatest chances of triggering avalanches on wind loaded NW-N-NE-E aspects 35 degrees and steeper. The avalanche danger is MODERATE below treeline in open areas 35 degrees and steeper. Human triggered avalanches are still possible today especially with larger triggers such as more than one person on a slope or a snowmobile. It is also still possible for avalanches triggered today to be large and have dire consequences.

One more small system should pass through the region tonight bringing scattered snow showers without any significant accumulations. After that the high pressure ridge begins to move into the area. The cold air should remain over the area through tonight. By tommorrow evening temperatures should start warming, and by the weekend they should be back up into the normal range. The ridgetop winds should continue from the west until the northerly flow arrives with the ridge.

Small snow showers yesterday brought another few inches of snow to the Sierra Crest. This snow fell as cold, light powder as did the snow on Tuesday night. This snow did not add much load to the snowpack. Yesterday's layer bonding tests again showed some improvement as many of the weaknesses created during the recent storm start to consolidate.

The biggest worry continues to be the large, stiff windslabs that started forming due to the high storm winds. There are still copious amounts of unconsolidated snow available for transport and the wind continues to blow at a consistant 35 mph. New windloading will cause these windslabs to continue to grow all dimensions: depth, width, and extent down slope. These windslabs are stiff and hard and will easily transmit force over longer distances. Again some steep, windloaded test slopes failed with a skiers weight and shooting cracks occured on similar pockets of terrain. Other test slopes failed after several jumps on the slope or when more than one person weighted the slope. Most of these test slopes were triggered in areas where the slab was thinnest and then stepped down into other layers in the storm snow or propagated out to areas where the slabs were thicker.

While these slabs are getting harder to trigger, it is still possible for them to be triggered by humans especailly above treeline in wind loaded areas on NW-N-NE-E aspects, 35 degrees and steeper. Larger triggers like having more than one person on a slope or snowmobiles will also be more likely to trigger these stubborn slabs. Any avalanches that occur today could step down from failures in the new snow to the old snow surfaces at the base of the storm snow. This would result in large, hard slabs that would have serious consequences.

Avalanches reported yesterday required slightly larger triggers. Many avalanches occurred in response to explosives, hard ski cuts, and large blocks of cornices that were knocked down onto the slopes. Most of these slides occurred due to failures of weaknesses in the storm snow. Several of the avalanches stepped down to the old snow surfaces.

The bottom line: Avalanche danger near and above treeline is MODERATE with the greatest chances of triggering avalanches on wind loaded NW-N-NE-E aspects 35 degrees and steeper. The avalanche danger is MODERATE below treeline in open areas 35 degrees and steeper. Human triggered avalanches are still possible today especially with larger triggers such as more than one person on a slope or a snowmobile. It is also still possible for avalanches triggered today to be large and have dire consequences.

At this time, we are still short $4,000 in funding for our operating budget this winter. If you use this service with any regularity and would like to continue to do so, please show your financial support for the Sierra Avalanche Center. You may make a tax deductible donation directly to us via Paypal or by sending a check to our address listed above, c/o the Truckee Ranger Station. The financial graph showing the amount of fundraising completed this season and our overall budget was updated today. It is available by clicking here. The financial support already received this winter from a variety of users is greatly appreciated.

Andy Anderson , Avalanche Forecaster
Today's Central Sierra Weather Observations:
0600 temperature at Sierra Crest (8,700 feet):
10 deg. F
Max. temperature at Sierra Crest past 24 hours:
17 deg. F
Average wind direction at Sierra Crest past 24 hours:
Westerly
Average wind speed at Sierra Crest past 24 hours:
35 mph
Maximum wind gust at Sierra Crest past 24 hours:
77 mph
New snow fall at 8,200 feet past 24 hours:
2 inches
Total snow depth at 8,200 feet:
108 inches
Mountain Weather Forecast For Today:
Partly cloudy with scattered snow showers.
Temperature forecast for 8,000 to 9,000 feet:
18 to 22 degrees F.
Ridgetop winds forecast for the Sierra Crest:
West 25-35 mph, gusting to 50 mph.
Snowfall expected in the next 24 hours:
trace
2 Day Mountain Weather Forecast:

7000 to 8000 Feet
Today, partly cloudy with scattered snow showers. Winds out of the southwest at 15 to 25 mph with gusts to 35 mph. Daytime highs 22 to 26 degrees F. Tonight, partly cloudy with scattered snow showers. Winds shifting to the east at 10 to 15 mph after midnight. Overnight lows 12 to 14 degrees F. Friday, partly cloudy and clearing in the afternoon. East winds at 10 to 15 mph are expected. Daytime highs 32 to 36 degrees F.

Above 8000 Feet
Today, partly cloudy with scattered snow showers. Winds out of the west at 25 to 35 mph with gusts to 50 mph. Daytime highs 18 to 22 degrees F. Tonight, partly cloudy with scattered snow showers. Winds of the west and northwest at 15-25 mph with gusts to 35 mph after midnight. Overnight lows around 22 degrees F. Friday, partly cloudy and clearing in the afternoon. Winds shifting to the east at 10 to 15 mph. Daytime highs around 32 degrees F.

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.