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, March 19th, 2007 at 7:00 am

The bottom line: This morning, avalanche danger is LOW for all aspects and elevations. As daytime warming occurs, isolated pockets of MODERATE avalanche danger will develop at all elevations on E-SE-S-SW aspects 35 degrees and steeper that are exposed to the sun today.

The southwest winds have started to increase, and the temperatures have started to cool as the high pressure ridge is finally being replaced by a low pressure system. The main effect of this storm will be to push temperatures back down to normal for this time of year for the next few days. It should also bring a small amount of precipitation: 5-8 inches of snow above 7000'. There could be some scattered showers this afternoon and evening, but the accumulation should mostly start after midnight tonight. The most significant snowfall should occur during the day on Tuesday. As this cold front moves in, today should become increasingly cloudy and temperatures should peak around midday and then begin to fall.

For the first time in over a week overnight low temperatures dropped below freezing in the mountains. Another clear night and these freezing temperatures should allow a much more robust refreeze to occur in the snowpack. The air temperatures are forecasted to peak at about 5 degrees cooler than yesterday around 11AM this morning. The sun is forecasted to become more and more obscured by increasing clouds today. A good freeze overnight, less sun, and cooler temperatures should cause the snow surface to only soften in areas on E-SE-S-SW aspects that do see the sun this morning. Even these areas should not soften as much today as they have been doing for the last week.

The daily melt-freeze cycles and isothermal conditions in the upper snowpack continue to promote uniformity in the snowpack. In the long run this trend will help to strengthen the snowpack. Today the melting part of this process should have a much less intense peak due to less sun and cooler temperatures. Therefore, less water will be percolating through the snowpack causing bonds to dissolve between the snow grains. This diminished melting should result in less widespread wet snow instability that endures for less time today. Isolated areas on E-SE-S-SW aspects that are exposed to the sun this morning will have the most chance to exhibit wet snow instability. Isolated areas where water can percolate to a smooth surface like a slab of rock and then flow along that surface lubricating it, and around glide cracks have the potential for wet slab avalanches to occur. Human triggering of loose wet snow sluffs and isolated wet slab avalanches is possible today.

With new snow and strong winds forecasted overnight and into tomorrow the avalanche danger will change in location and severity. Depending on how fast the snow surface refreezes before new snow starts accumulating on it, there may be an issue with how well the new snow bonds to the current surface. Tomorrow newly formed wind slabs could become an issue on aspects that have not needed much worry over the last week or two.

For today: pay attention to signs of surface instability like pinwheels and rollerballs. Step off of your equipment and check boot penetration as daytime warming occurs. Avoid steep slopes where boot penetration exceeds boot top height. Human triggered wet snow avalanche activity will become possible today as daytime warming occurs. Natural wet snow avalanche activity is unlikely.

The bottom line: This morning, avalanche danger is LOW for all aspects and elevations. As daytime warming occurs, isolated pockets of MODERATE avalanche danger will develop at all elevations on E-SE-S-SW aspects 35 degrees and steeper that are exposed to the sun today.

Our next fundraiser will occur on March 25th at Sugar Bowl Ski Area. For more information, click here or visit our homepage by clicking on the toolbar up top. At this time, we are still short $2,000 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 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.

Andy Anderson , Avalanche Forecaster
Today's Central Sierra Weather Observations:
0600 temperature at Sierra Crest (8,700 feet):
31 deg. F
Max. temperature at Sierra Crest past 24 hours:
50 deg. F
Average wind direction at Sierra Crest past 24 hours:
Southwesterly
Average wind speed at Sierra Crest past 24 hours:
25 mph
Maximum wind gust at Sierra Crest past 24 hours:
39 mph
New snow fall at 8,200 feet past 24 hours:
0 inches
Total snow depth at 8,200 feet:
68 inches
Mountain Weather Forecast For Today:
Partly cloudy this morning becoming mostly cloudy by this afternoon.
Temperature forecast for 8,000 to 9,000 feet:
42 to 48 degrees F.
Ridgetop winds forecast for the Sierra Crest:
Southwesterly 30-40 mph with gusts to 60mph.
Snowfall expected in the next 24 hours:
1-2 inches
2 Day Mountain Weather Forecast:

7000 to 8000 Feet:
Today, partly cloudy this morning becoming mostly cloudy by this afternoon. Daytime highs 49 to 55 degrees F. Southwest winds at 15 to 25 mph with gusts to 35 mph. Tonight, cloudy with scattered snow showers. Accumulation of 1-2 inches. Overnight lows 25 to 30 degrees F. Southwest winds at 20 to 30 mph with gusts to 40 mph. Tuesday, snow with accumulations of up to 4 inches. Daytime highs 35 to 40 degrees F. Southwest winds at 20 to 30 mph with gusts to 40 mph are expected.

Above 8000 Feet:
Today, partly cloudy this morning becoming mostly cloudy by this afternoon. Daytime highs 42 to 48 degrees F. Southwest winds at 30 to 40 mph with gusts to 60 mph. Tonight, cloudy with scattered snow showers. Accumulation of 1-2 inches. Overnight lows 22 to 27 degrees F. Southwest winds at 30 to 40 mph with gusts to 70 mph. Tuesday, snow with accumulations of up to 6 inches. Daytime highs 30 to 35 degrees F. Southwest winds at 25 to 35 mph with gusts to 60 mph 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.