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, March 17th, 2007 at 7:00 am

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

Record high temperatures are still possible for today. These above normal temperatures should gradually begin to cool as the high pressure over the region begins to break down. A small, weak low pressure system should bring some cloud cover and slightly cooler temperatures starting this evening and continuing through tomorrow. It is the precursor to a larger low pressure system that should bring some precipitation to the area starting later in the day on Monday. The winds shifted to the southwest yesterday and should remain light through the weekend.

Air temperatures have been above freezing for 24 hours a day for a full week. Last night the low temperatures along the Sierra Crest were around 45 degrees F and in the Mt. Rose area they were around 41 degrees F. The upper 3-4 inches of the snowpack continues to refreeze overnight due to radiational cooling. Wet, unfrozen snow persists from day to day underneath this crust layer. The daily melt-freeze cycles and isothermal conditions in the upper snowpack continue to allow the layers in the upper snowpack to become more uniform. There are still a few areas at higher elevations where some less dense layers of snow exist in the upper 1-2ft of the snowpack. These less dense layers could serve as weak layers for wet snow avalanche activity as the the day warms up, and they become saturated with water. Most of the weak layers buried in the snowpack are rounding and becoming well bonded. There are a few areas where faceted layers still exist deep in the snowpack. As the temperatures continue to stay warm and water percolates down to these layers, they could weaken to the point of failure producing wet slab avalanches. Even though these slides are likely to be fairly rare and isolated, they are extremely hard to predict and would be very dangerous so they warrant more caution. Warming instability that does occur today is expected to be limited to human triggering of wet surface snow.

The surface snow has made to transition from wet new snow crystals to true corn snow in many sun exposed areas. As a result, roller ball and pinwheel activity have decreased, but still occur during the afternoon hours in response to human triggers. Pay attention to signs of surface instability. Step off of your equipment and check boot penetration as daytime warming occurs. Avoid steep slopes where boot penetration exceeds boot top height. Yesterday human triggered whumphing was observed on S-SW slopes around 8500' from midday on as water in the snowpack caused layers to weaken. Human triggered wet snow avalanche activity will become possible today as daytime warming occurs. Natural wet snow avalanche activity is unlikely, but not impossible.

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

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):
45 deg. F
Max. temperature at Sierra Crest past 24 hours:
60 deg. F
Average wind direction at Sierra Crest past 24 hours:
Southwesterly
Average wind speed at Sierra Crest past 24 hours:
20 mph
Maximum wind gust at Sierra Crest past 24 hours:
40 mph
New snow fall at 8,200 feet past 24 hours:
0 inches
Total snow depth at 8,200 feet:
72 inches
Mountain Weather Forecast For Today:
Sunny skies
Temperature forecast for 8,000 to 9,000 feet:
55 to 65 degrees F.
Ridgetop winds forecast for the Sierra Crest:
Southwesterly 10-20 mph.
Snowfall expected in the next 24 hours:
0 inches
2 Day Mountain Weather Forecast:

7000 to 8000 Feet:
Today, sunny skies with daytime highs 62 to 67 degrees F. Southwest winds at 5 to 15 mph. Tonight, partly cloudy skies with overnight lows 35 to 45 degrees F. Southwest winds at 5 to 15 mph. Sunday, partly cloudy skies with daytime highs 55 to 60 degrees F. West winds at 5 to 15 mph are expected.

Above 8000 Feet:
Today, sunny skies with daytime highs 55 to 65 degrees F. Southwest winds at 10 to 20 mph. Tonight, partly cloudy skies with overnight lows 35 to 45 degrees F. Southwest winds at 10 to 20 mph. Sunday, partly cloudy skies with daytime highs 48 to 58 degrees F. West winds at 10 to 20 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:
	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.