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 Sunday, February 25th, 2007 at 6:56 am

The bottom line: Near and above treeline, avalanche danger is HIGH on wind loaded NW-N-NE-E aspects 32 degrees and steeper. Below treeline avalanche danger is MODERATE with pockets of CONSIDERABLE in open areas 35 degrees and steeper.

The current storm system began to impact the forecast area yesterday afternoon. This storm is creating strong ridgetop winds and significant snowfall rates across the forecast area this morning. Snowfall accumulation and snowfall rates are expected to increase as the day progresses. Ridgetop winds are expected to remain strong westsouthwesterly through tonight. Another, powerful storm system is following behind the current system and is expected to arrive Monday afternoon.

The storm snow from 2/21-2/22 has bonded very well to the old snow surface below it. Yesterday, layer bonding tests continued to yield easy to moderate shears within the upper 1 foot of the snowpack. An additional 11-17 inches of 9-11% density new snow load has been added to these layers overnight. Very easy shear failure has been observed this morning within the new snow from overnight. Layers of graupel are evident within the new snow in many locations and are active failure layers this morning.

Wind slab formation increased yesterday above treeline as snowfall rates decreased and ridgetop wind speeds increased. These wind slabs will receive significant new snow loading during the day today. These slabs sit on top of lower density snow. This is creating ideal conditions for avalanche activity. Failure of these newly formed and loaded wind slabs could create avalanches with crowns that measure 2-4 feet deep by this afternoon.

Heavy snowfall rates will combine with significant wind loading today to create widespread snowpack instability near and above treeline. Human triggered avalanches are likely in wind loaded areas on NW-N-NE-E aspects, 32 degrees and steeper. Natural avalanches are likely in this same terrain on slopes 35 degrees and steeper.

The bottom line: Near and above treeline, avalanche danger is HIGH on wind loaded NW-N-NE-E aspects 32 degrees and steeper. Below treeline avalanche danger is MODERATE with pockets of CONSIDERABLE in open areas 35 degrees and steeper.

At this time, we are still short $7,000 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. A financial graph showing the amount of fundraising completed this season and our overall budget is available by clicking here. The financial support already received this winter from a variety of users is greatly appreciated.

Brandon Schwartz, Avalanche Forecaster

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Today's Central Sierra Weather Observations:
0600 temperature at Sierra Crest (8,700 feet): 17 deg. F
Max. temperature at Sierra Crest past 24 hours: 21 deg. F
Average wind direction at Sierra Crest past 24 hours: Westsouthwesterly
Average wind speed at Sierra Crest past 24 hours: 56 mph
Maximum wind gust at Sierra Crest past 24 hours: 135 mph
New snow fall at 8,200 feet past 24 hours: 11 - 17 inches
Total snow depth at 8,200 feet: 69 inches

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Mountain Weather Forecast For Today:
Cloudy with heavy snowfall.
Temperature forecast for 8,000 to 9,000 feet: 23 to 29 degrees F.
Ridgetop winds forecast for the Sierra Crest: Westsouthwesterly 55-65 mph, gusting over 100 mph.
Snowfall expected in the next 24 hours: 12 - 24 inches

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2 Day Mountain Weather Forecast:
7000 to 8000 Feet
Today, cloudy with snow, heavy at times. Snow accumulation 6 to 12 inches. West winds at 15 to 25 mph gusting to 50 mph. Daytime highs 28 to 34 degrees F. Tonight, cloudy with snow. Snow accumulation 3 to 6 inches. West winds 25 to 35 mph, gusting to 45 mph. Overnight lows around 15 degrees F. Monday, cloudy with snow. Snow accumulation 4 to 8 inches. Southwest winds at 25 to 35 mph with gusts to 55 mph in the afternoon are expected. Daytime highs around 30 degrees F.

Above 8000 Feet
Today, cloudy with heavy snowfall. Snow accumulation 8 to 16 inches. Westsouthwest winds at 55 to 65 mph, gusting over 100 mph. Daytime highs around 26 degrees F. Tonight, cloudy with snow. Snow accumulation 4 to 8 inches. Southwest winds 50 to 60 mph, gusting to 90 mph. Overnight lows around 12 degrees F. Monday, cloudy with snow. Snow accumulations 5 to 10 inches. Southwest winds at 45 to 55 mph with gusts to 100 mph are expected. Daytime highs around 24 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:
	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.