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 10th, 2007 at 7:15 am

The bottom line: Near and above treeline, avalanche danger is CONSIDERABLE. Human triggered avalanches with crowns of 2 to more than 5 ft are probable and natural avalanche activity is possible today. Avalanche activity is most likely on wind loaded NW-N-NE-E aspects 32 degrees and steeper. Below treeline, avalanche danger is MODERATE. Near and below 8000' some point release and small wet slab activity will be the most likely type of avalanche activity on steep slopes at all aspects.

Subtropical moisture continues to pour into the central Sierras bringing warm air and rain with it. Snow levels climbed to 8000' this morning and are expected to remain there until they start to drop tonight. By tomorrow afternoon snow level is forecasted to drop to lake level. By that time most of the moisture will have passed through the area, and we should only see a few more inches of snow on Sunday. Until then we should continue to get significant accumulation above 8000'. Up to 12 inches is forecasted for today with another 4-8 inches overnight tonight. Southwesterly ridgetop winds are expected to remain in the 30 to 40 mph range today, which will continue provide ideal conditions for building cornices and wind loading many of our avalanche starting zones. The winds are forecasted to increase tonight and should remain a little stronger through Sunday.

Above 8000' we have gotten between 17 and 20 inches of snow out of this storm cycle with more on the way today. Along the Sierra crest above treeline the consistent SW winds at 30-40mph associated with this storm have been perfect for creating some deep, heavy windslabs and some large cornices on the NW-N-NE-E aspects. As it continues to blow and snow today, we should see these windslabs become larger and more widespread. Even though the new snow is bonding well to the old snow surfaces and consolidating relatively quickly, these windslabs are still reactive. Human triggering of these slabs is probable, and we may even see some natural avalanches occurring on the most heavily wind loaded slopes today. These slabs could easily be up to 6 or 7 feet deep in some places. Yesterday one of these windslabs was triggered with an explosive and resulted in an avalanche with a 5 ft crown. Watch out for any windloaded terrain. You can use clues like cornices, blowing snow, drifted snow, ripples, and other wind created features to help you recognize wind loaded slopes. Most of the avalanche activity today will probably occur within the new snow on weaknesses that formed during the storm as the weather conditions changed slightly. The other avalanche concern for today is the rising freezing levels and rain. This rapid warming and rain on new snow could easily destabilize the new snow and allow wet avalanche activity to occur below 8000' today on all aspects and slopes steeper than 35 degrees. As the day continues and we get more snow the avalanche danger will become more widespread and avalanches will likely become larger. Be careful out there and choose your terrain wisely.

Yesterday numerous avalanches up to 5 ft in depth were reported on northerly wind loaded slopes. These avalanches were triggered both by ski cutting, explosives, and cornices collapsing onto the slopes. Yesterday some point release avalanches on slopes steeper than 35 degrees below 8000' yesterday were also observed.

The bottom line: Near and above treeline, avalanche danger is CONSIDERABLE. Human triggered avalanches with crowns of 2 to more than 5 ft are probable and natural avalanche activity is possible today. Avalanche activity is most likely on wind loaded NW-N-NE-E aspects 32 degrees and steeper. Below treeline, avalanche danger is MODERATE. Near and below 8000' some point release and small wet slab activity will be the most likely type of avalanche activity on steep slopes at all aspects.

With the return of precipitation to the forecast area, we will resume posting advisories each morning, prior to 7am.

At this time, we have not raised enough money to meet our operating budget for this year. If you use this service with any regularity and would like to continue to do so, please show your 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. We updated the financial graph with the current fund-raising numbers for more details, click 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):
32 deg. F
Max. temperature at Sierra Crest past 24 hours:
32 deg. F
Average wind direction at Sierra Crest past 24 hours:
southwesterly
Average wind speed at Sierra Crest past 24 hours:
30 mph
Maximum wind gust at Sierra Crest past 24 hours:
49 mph
New snow fall at 8,200 feet past 24 hours:
8 inches
Total snow depth at 8,200 feet:
45 inches
Mountain Weather Forecast For Today:
Snow with accumulation of up to 12 ".
Temperature forecast for 8,000 to 9,000 feet:
28-33 deg. F
Ridgetop winds forecast for the Sierra Crest:
Southwesterly 25 - 35 mph, gusting to 75 mph
Snowfall expected in the next 24 hours:
12 - 20 inches
2 Day Mountain Weather Forecast:

7000 to 8000 Feet
Mostly rain with snow near 8000'. Snow with accumulations of up to 6 inches near 8000'. Snow level 8000'. Southwest winds at 10 to 20 mph. Daytime highs 32 to 37 degrees F. Tonight, snow accumulation up to 6 inches. Snow level starting to drop after midnight. Lows 27 to 32 degrees F. Southwest winds at 10 to 20 mph. Tomorrow, snow with accumulations of up to 4 ". Snow level should drop to lake level by the early morning. Southwest winds at 10 to 20 mph. Daytime highs 29 to 34 degrees F.

Above 8000 Feet
Snow with accumulations of 8 to 12 inches. Southwest winds at 30 to 40 mph, gusting to 45 mph and increasing to 70mph gusts by this afternoon. Daytime highs 28 to 33 degrees F. Tonight, snow with accumulation of 4 to 8 inches. Lows around 25 degrees F. Southwest winds at 40 to 50 mph with gusts between 80 and 100mph. Tomorrow, snow with accumulations of 3 to 6 inches. Southwest winds at 35 to 45 mph with gusts to 80. Daytime highs 24 to 30 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.