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 Saturday, February 24th, 2007 at 6:59 am

The bottom line: This morning, avalanche danger near and above treeline is MODERATE on wind loaded NW-N-NE-E aspects 35 degrees and steeper. Below treeline avalanche danger is LOW. Avalanche Danger is expected to increase to CONSIDERABLE near and above treeline late today and during the overnight hours.

The recent storm system that affected the forecast area over the past few days has moved off to the east, leaving a small amount of moisture behind. Yesterday, this moisture produced continued snow showers over the Sierra Crest. Lingering snow showers are expected again today before another storm system impacts the forecast area beginning late today and continuing through Sunday. Moderate ridgetop winds were westerly during the day yesterday and shifted to light northwesterly overnight. Ridgetop winds are expected to shift to southwesterly and increase in wind speed, becoming strong by late today.

Storm totals from the the past three days have been measured at 24-30 inches along the Sierra Crest and up to 12 inches in the Mount Rose area. Most avalanche activity observed during the storm was in the form of loose snow and soft slab avalanches. The lower than average density of the recent snow (around 5%) contributed to less cohesive slab formation than is often observed in our area. Avalanche activity was limited to wind loaded areas and steep open areas below treeline. Cornice features have increased in size and are fairly weak. Widespread natural cornice collapse was observed yesterday, while human triggered cornice collapse was able release cornice chunks ranging from the size of a refrigerator to a small car. These cornice sections were able to trigger soft slab avalanches within in storm snow. Minimal slab propagation was observed yesterday.

The storm snow showed a significant increase in bond strength at the old snow/storm snow interface yesterday as compared to Thursday. A variety of shears were observed within the storm snow, with most natural avalanche activity occurring within the top one foot of the snowpack. Explosive control work yesterday created snowpack failure within the lower half of the storm snow. Human triggered sluffs were observed below treeline in steep open areas.

Significant wind loading was observed throughout the day yesterday on NW-N-NE-E aspects above treeline. Increasing ridgetop winds today will cause continued wind loading as significant amounts of snow remain available for wind transport. Sensitive wind slabs will exist again today above treeline. Human triggered avalanches remain possible today in wind loaded areas on NW-N-NE-E aspects, 35 degrees and steeper. Natural avalanches are unlikely this morning. Avalanche danger will increase late today near and above treeline on NW-N-NE-E aspects, 35 degrees and steeper.

The bottom line: This morning, avalanche danger near and above treeline is MODERATE on wind loaded NW-N-NE-E aspects 35 degrees and steeper. Below treeline avalanche danger is LOW. Avalanche Danger is expected to increase to CONSIDERABLE near and above treeline late today and during the overnight hours.

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): 19 deg. F
Max. temperature at Sierra Crest past 24 hours: 19 deg. F at 2PM yesterday.
Average wind direction at Sierra Crest past 24 hours: Westerly
Average wind speed at Sierra Crest past 24 hours: 20 mph
Maximum wind gust at Sierra Crest past 24 hours: 47 mph
New snow fall at 8,200 feet past 24 hours: 1 - 3 inches
Total snow depth at 8,200 feet: 63 inches

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Mountain Weather Forecast For Today:
Mostly cloudy with a chance of snow, becoming likely in the afternoon.
Temperature forecast for 8,000 to 9,000 feet: 23 to 29 degrees F.
Ridgetop winds forecast for the Sierra Crest: West 20-30 mph gusting to 60 mph.
Snowfall expected in the next 24 hours: 8 - 14 inches

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2 Day Mountain Weather Forecast:
7000 to 8000 Feet
Today mostly cloudy with snow becoming likely in the afternoon. Snow accumulation up to 1 inch. West winds at 10 to 20 mph gusting to 30 mph in the afternoon. Daytime highs 32 to 38 degrees F. Tonight, cloudy with snow. Snow accumulation 8 to 12 inches. West winds 25 to 35 mph, gusting to 55 mph. Overnight lows around 23 degrees F. Sunday, cloudy with snow. Snow accumulations 6 to 12 inches. West winds at 30 to 40 mph with gusts to 60 mph are expected. Daytime highs around 31 degrees F.

Above 8000 Feet
Today mostly cloudy with a chance of snow, becoming likely in the afternoon. Snow accumulation up to 1 inch. Northwest winds at 15 to 20 mph, gusting to 50 mph. Winds shifting to west at 20 to 30 mph gusting to 60 mph in the afternoon. Daytime highs around 29 degrees F. Tonight, cloudy with snow. Snow accumulation 8 to 14 inches. Southwest winds 60 to 70 mph, gusting to 120 mph. Overnight lows around 20 degrees F. Sunday, cloudy with snow. Snow accumulations 6 to 14 inches. Southwest winds at 55 to 65 mph with gusts to 120 mph are expected. Daytime highs around 26 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:
	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.