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 Monday, April 9th, 2007 at 6:47 am

The bottom line: Early this morning, avalanche danger is LOW for areas where an overnight snow surface refreeze occurred. In areas where no overnight refreeze occurred, avalanche danger is MODERATE on slopes 35 degrees and steeper early this morning. As daytime warming occurs, MODERATE avalanche danger will develop above 8,500' on all E-SE-S-SW aspects 35 degrees and steeper. Below 8,500', MODERATE avalanche danger will develop on all snow covered aspects, 35 degrees and steeper.

The weak weather system is moving through the northern half of the forecast area this morning. Very light rain and snow began north of Hwy 50 along the Sierra Crest around 3:30am. Rain and snow shower activity is expected to dissipate rapidly after sunrise. In the northern half of the forecast area, skies will become increasingly clear as the day progresses. South of Hwy 50, less overnight cloud cover and no precipitation was observed. In the southern half of the forecast area, sunny skies are expected all day. Moderate to strong westerly ridgetop winds were observed throughout the forecast area during the overnight hours.

The passing weather system will create differing snowpack conditions from one portion of the forecast area to another today. Along the Sierra Crest north of Hwy 50, snow level is running around 7,800' this morning. Only a very thin and weak refreeze of the snow surface has been observed above 8,000' this morning. Below 8,000', rain has kept the snow surface from refreezing.

Along the Sierra Crest south of Hwy 50, reduced cloud cover has allowed for better radiational cooling despite air temperatures above freezing at the 8,500' level. A decent, but not particularly thick surface refreeze is expected in this area. In the Mount Rose area, overnight air temperatures fell well below freezing for the second night in a row, creating a solid snow surface refreeze.

The snow surface will soften rapidly this morning as daytime warming occurs, especially in areas where only a weak refreeze or no refreeze of the snow surface occurred overnight. In areas where no surface refreeze occurred overnight, human triggered avalanches are possible during the early morning hours today. Once the supportable surface crust in other areas is gone, snowpack instability will rapidly increase. As the surface crust melts, human triggered avalanches will become possible today above 8,500' on E-SE-S-SW aspects, 35 degrees and steeper. Below 8,500', human triggered avalanches will become possible on all snow covered aspects, 35 degrees and steeper.

Wet snow exists throughout the snowpack below 8,500' on all aspects in the forecast area. Isolated areas of a more winter like snowpack exist above 9,000' on NW-N-NE aspects. Despite May like air temperatures for the past month, the sun angle of March and early April has kept solar radiation on steep northerly aspects to a minimum. Excellent corn snow conditions can be found on a variety of aspects during the morning hours.

Keep in mind that when boot penetration in wet snow exceeds boot top height, human triggered wet snow avalanches are possible in that area. Step off of your equipment on a regular basis to check boot penetration. When evidence of wet snow instability such as deep boot penetration or pinwheels larger than 1 foot in diameter develop, move to a less sun affected aspect or call it a day.

The bottom line: Early this morning, avalanche danger is LOW for areas where an overnight snow surface refreeze occurred. In areas where no overnight refreeze occurred, avalanche danger is MODERATE on slopes 35 degrees and steeper early this morning. As daytime warming occurs, MODERATE avalanche danger will develop above 8,500' on all E-SE-S-SW aspects 35 degrees and steeper. Below 8,500', MODERATE avalanche danger will develop on all snow covered aspects, 35 degrees and steeper.

We will raffle a BCA backpack, beacon, shovel, and probe package on April 17th as a way to say thanks to everyone who has sent us a donation in the mail or via Pay Pal this season. All individuals who have donated $10 or more to SAC are automatically entered in this raffle. Thanks to all of our sponsors, the ski days, and everyone who has donated funding this winter, we have met our operating budget for this season and have a start on next year's funding. For more details about our financial situation please click here.

Brandon Schwartz, Avalanche Forecaster

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Today's Central Sierra Weather Observations:
0600 temperature at Sierra Crest (8,700 feet): 30 deg. F
Max. temperature at Sierra Crest past 24 hours: 44 deg. F
Average wind direction at Sierra Crest past 24 hours: Westerly
Average wind speed at Sierra Crest past 24 hours: 36 mph
Maximum wind gust at Sierra Crest past 24 hours: 66 mph over the Crest. Wind gusts to 97 mph over the Carson Range.
New snow fall at 8,200 feet past 24 hours: 0 - trace inches
Total snow depth at 8,200 feet: 54 inches

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Mountain Weather Forecast For Today:
Mostly cloudy in the morning, clearing by afternoon in the north. Sunny all day in the south.
Temperature forecast for 8,000 to 9,000 feet: 36 - 44 degrees F.
Ridgetop winds forecast for the Sierra Crest: Westerly at 30 to 50 mph, gusting 80 mph, decreasing in the afternoon.
Snowfall expected in the next 24 hours: 0 inches

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2 Day Mountain Weather Forecast:
7000 to 8000 Feet:
Today, clear to partly cloudy skies with daytime highs 42 to 50 degrees F. Southwest winds at 25 to 35 mph, decreasing to 15 to 25 mph in the afternoon. Tonight, clear skies with overnight lows around 26 degrees F. West winds at 15 to 25 mph, gusting to 35 mph, decreasing to 10 to 15 mph after midnight. Tuesday, partly cloudy skies with daytime highs 37 to 45 degrees F. West winds at 15 to 20 mph are expected.

Above 8000 Feet:
Today, clear to partly cloudy skies with daytime highs 36 to 44 degrees F. West winds at 30 to 50 mph, gusting to 80 mph. West winds decreasing to 20 to 30 mph with gusts to 60 mph by afternoon. Tonight, clear skies with overnight lows around 26 degrees F. West winds at 20 to 35 mph, gusting to 60 mph. Tuesday, partly cloudy skies with daytime highs 31 to 39 degrees F. West winds at 20 to 35 mph, gusting to 50 mph in the morning are expected.

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.