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 Thursday, April 5th, 2007 at 7:00 am

The bottom line: This morning, avalanche danger is LOW for all elevations and aspects. As daytime warming occurs, avalanche danger will rise to MODERATE above 8,000' on sun exposed E-SE-S-SW aspects 35 degrees and steeper. Below 8,000', avalanche danger will rise to MODERATE on all snow covered aspects, 35 degrees and steeper. If it does rain today the avalanche danger will rise to MODERATE on any slopes that receive rain and are steeper than 35 degrees.

The broken, thin clouds persisted overnight. As the low pressure system near southern California begins to pull moisture into the area more clouds should form throughout the day. Warm air moving into the forecast area should cause temperatures to climb even higher today and tomorrow. This warm surface air may also contribute to some instability in the atmosphere that could allow for a slight chance for some isolated rain showers and thunder storms to develop through tomorrow. The more consistent cloud cover should keep overnight temperatures higher and should prevent strong refreezes of the snowpack due to radiation cooling over night. Winds should continue to decrease and shift to the south today and tomorrow.

After climbing into the 50's at upper elevations yesterday, the air temperatures only fell into the mid 40's overnight throughout the forecast area last night. The radiational refreeze of the snowpack should have been much weaker last night than it has been all week due to the increased cloud cover and warmer air temperatures. Even though continued cloud cover is forecasted for today the weaker refreeze means that the snowpack should still soften and melt today. In areas where the snowpack is exposed to the sun the snow surface will soften quickly and a deeper layer of wet unconsolidated snow will form in comparison to previous days. In areas where the cloud cover persists this melting should take slightly longer. This melting will create free water in the snowpack that will weaken the snowpack and create areas of wet snow instability. If rain showers do materialize anywhere in the forecast area, they will contribute more free water to the snowpack causing the areas of wet snow instability to become more widespread.

Snow surface conditions vary widely from rough and bumpy to smooth and enjoyable. The warm, sunny weather has caused daily melt-freeze cycles to occur in most of the forecast area. The only areas that are still holding on to winter are northerly aspects above 10,000'. Many northerly aspects above 9,000' have not undergone enough melt-freeze cycles for the snow from the last storm to become high quality corn snow. In these areas only a thin melt-freeze crust exists on the snow surface. Human triggered rollerballs and pinwheels were observed on these slopes in the Carson Pass area yesterday. Below 9,000', excellent corn snow conditions can be found mid morning in many areas, especially on E and SE aspects.

Any avalanche activity is unlikely prior to mid morning unless some rain showers occur. If it does rain today the human triggered avalanches will be possible on any slopes that receive rain and are steeper than 35 degrees. As daytime warming occurs, areas of wet snow instability will form on steep slopes, in a variety of areas. Human triggered avalanches will become possible above 8,000' on E-SE-S-SW aspects, 35 degrees and steeper. Below 8,000', human triggered avalanches will become possible on all snow covered aspects, 35 degrees and steeper.

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 soft and sloppy aspect or call it a day.

The bottom line: This morning, avalanche danger is LOW for all elevations and aspects. As daytime warming occurs, avalanche danger will rise to MODERATE above 8,000' on sun exposed E-SE-S-SW aspects 35 degrees and steeper. Below 8,000', avalanche danger will rise to MODERATE on all snow covered aspects, 35 degrees and steeper. If it does rain today the avalanche danger will rise to MODERATE on any slopes that receive rain and are steeper than 35 degrees.

The Heavenly Ski Patrol has been generous enough to include the Sierra Avalanche Center as one of the benefactors of their annual fundraising party this year. The party is this Friday, April 6th at the Horizon Casino Resort in South Lake Tahoe from 7pm to midnight. Tickets are $10 at the door. A portion of the proceeds will go to the SAC operating budget for next season. For more information please click here. We will also raffle off 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.

Andy Anderson , Avalanche Forecaster
Today's Central Sierra Weather Observations:
0600 temperature at Sierra Crest (8,700 feet):
46 deg. F
Max. temperature at Sierra Crest past 24 hours:
53 deg. F
Average wind direction at Sierra Crest past 24 hours:
Southwesterly
Average wind speed at Sierra Crest past 24 hours:
15 mph
Maximum wind gust at Sierra Crest past 24 hours:
46 mph
New snow fall at 8,200 feet past 24 hours:
0 inches
Total snow depth at 8,200 feet:
58 inches
Mountain Weather Forecast For Today:
Partly cloudy skies with a slight chance of isolated showers.
Temperature forecast for 8,000 to 9,000 feet:
50-58 degrees F.
Ridgetop winds forecast for the Sierra Crest:
Southwesterly shifting to the southeast at 10 to 15 mph
Snowfall expected in the next 24 hours:
0 inches
2 Day Mountain Weather Forecast:

7000 to 8000 Feet:
Today mostly cloudy skies with a slight chance of isolated showers. Daytime highs 54 to 62 degrees F. Southwest winds shifting to southeast winds around 10 mph. Tonight, mostly cloudy skies with a slight chance of isolated showers. Overnight lows 36 to 42 degrees F. Southeast winds around 10 mph. Friday, mostly cloudy skies with a chance of isolated thunderstorms in the afternoon. Daytime highs 55 to 63 degrees F. Light winds are expected.

Above 8000 Feet:
Today mostly cloudy skies with a slight chance of isolated showers. Daytime highs 50 to 58 degrees F. Southwest winds shifting to southeast winds at 10 to 15 mph. Tonight, mostly cloudy skies with a slight chance of isolated showers. Overnight lows 36 to 42 degrees F. South winds at 10 to 15 mph. Friday, mostly cloudy skies with a chance of isolated thunderstorms in the afternoon. Daytime highs 51 to 59 degrees F. South winds at 10 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:
	Thursday:	Thursday Night:	Friday:
Weather:
Temperatures:	deg. F.	deg. F.	deg. F.
Wind direction:
Wind speed:
Expected snowfall:	O in.	O in.	O in.
For 8000-9000 ft:
	Thursday:	Thursday Night:	Friday:
Weather:
Temperatures:	deg. F.	deg. F.	deg. F.
Wind direction:
Wind speed:
Expected snowfall:	O in.	O in.	O in.