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 12th, 2007 at 7:00 am

The bottom line: Avalanche danger is MODERATE on the NW-N-NE aspects and in areas sheltered from solar exposure today. The avalanche danger will rise to CONSIDERABLE on sun exposed E-SE-S-SW aspects with slopes steeper than 35 degrees below 8500' as natural wet snow avalanches become possible today due to daytime warming. Today is a good day to avoid those southerly slopes once they warm up. Use good snow assessment and safe travel techniques to minimize risks.

Many areas today are forecasted to reach record high temperatures. The high pressure ridge over the forecast area should allow clear weather with warm temperatures to persist through next week. After today temperatures should cool slightly, but they will still be well above normal. The days also continue to get longer and that means more solar radiation on the slopes. Warm air temperatures and lots of solar radiation translate to rapid melting of the snow. A small disturbance passing to the north should cause high thin clouds and stronger westerly ridgetop winds through mid week.

The overnight lows along the Sierra Crest last night were between 44 and 48 degrees F. In the Mt. Rose area the overnight low was around 42 degrees F. That is the second night in a row that temperatures never dropped below freezing in the mountains. Radiational cooling of the snowpack may allow the snow surface to refreeze in some places. With record high temperatures and lots of sun forecasted for today, the snow should soften very fast becoming wet and sloppy after a short time in the sun.

This warm springtime weather marks the first significant extended period of intense solar radiation and prolonged high air temperatures for the forecast area. The snowpack has not gone through enough cycles of melting and freezing for the temperatures throughout the snowpack to become uniform (isothermal) or for the layers in the snowpack to become more homogeneous. There are still several colder, more fine-grained, winter layers and crusts buried in the snowpack. As the snow starts to melt and water percolates down dissolving bonds between the snow grains, the water could easily collect in these locations. Water at these crust interfaces and colder, more fine-grained snow layers should weaken the bonds in these areas and allow them to serve as weak layers whose failure could cause wet snow avalanches. Surface instabilities like rollerballs and pinwheels indicate that this process is starting to take place. Another good indicator that the slope has warmed up to the point that wet avalanches may occur is when boot penetration exceeds ankle height. An easy way to check this is to step out of your skis. If you sink into wet snow to the top of your boots, it is time to move to a less sun exposed aspect or call it a day.

Roller balls and large human triggered pinwheels have been reported on the most of aspects over the last few days. No human triggered or natural wet snow avalanches have been reported, despite these signs of surface instability. As air temperatures continue to warm today, the possibility of wet snow avalanche activity will increase.

The bottom line: Avalanche danger is MODERATE on the NW-N-NE aspects and in areas sheltered from solar exposure today. The avalanche danger will rise to CONSIDERABLE on sun exposed E-SE-S-SW aspects with slopes steeper than 35 degrees below 8500' as natural wet snow avalanches become possible today due to daytime warming. Today is a good day to avoid those southerly slopes once they warm up. Use good snow assessment and safe travel techniques to minimize risks.

At this time, we are still short $3,000 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):
48 deg. F
Max. temperature at Sierra Crest past 24 hours:
57-60 deg. F
Average wind direction at Sierra Crest past 24 hours:
Easterly shifting to westerly early this morning
Average wind speed at Sierra Crest past 24 hours:
15-20 mph
Maximum wind gust at Sierra Crest past 24 hours:
29 mph
New snow fall at 8,200 feet past 24 hours:
0 inches
Total snow depth at 8,200 feet:
83 inches
Mountain Weather Forecast For Today:
Sunny skies
Temperature forecast for 8,000 to 9,000 feet:
51 to 57degrees F.
Ridgetop winds forecast for the Sierra Crest:
Westerly 10-15 mph.
Snowfall expected in the next 24 hours:
0 inches
2 Day Mountain Weather Forecast:

7000 to 8000 Feet

Today, sunny with daytime highs 57 to 63 degrees F. West winds at 10 to 15 mph. Tonight, clear skies with overnight lows 31 to 37 degrees F. West winds at 10 to 15 mph. Tuesday, sunny skies with daytime highs 55 to 61 degrees F. West winds at 10 to 15 mph with gusts to 30 mph are expected.

Above 8000 Feet

Today, sunny with daytime highs 51 to 57 degrees F. West winds at 10 to 15 mph. Tonight, clear skies with overnight lows around 37 degrees F. West winds at 10 to 15 mph. Tuesday, sunny skies with daytime highs 49 to 55 degrees F. West winds at 20 to 30 mph with gusts to 50 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.