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 12th, 2007 at 7:00 am

The bottom line: The avalanche danger is MODERATE near and above treeline today. The most suspect areas will be on windloaded N-NE-E-SE aspects 35 degrees and steeper. Below treeline the avalanche danger should remain LOW with some isolated pockets of MODERATE avalanche danger on open, windloaded slopes 35 degrees and steeper. Both loose snow sluffs and slab avalanches are possible today. Use safe backcountry travel techniques, and re-assess snowpack conditions on a regular basis. Remember to be flexible and willing to change your plans when conditions change.

The cold front has moved into the area and will start moving to the east today. Snow showers will taper off today as the sky clears and a high pressure ridge starts to build. The cold front should remain over the forecast area long enough to keep temperatures cold today. The ridge should be in place by tomorrow, and temperatures should jump back into the mid 40's with lots of intense spring sunshine. As the cold front moves east today the winds should start to shift to the north and east. They are forecasted to be moderate and diminish as the ridge builds over the area tomorrow. The next disturbance that could cool things down and bring a little more snow is forecasted to arrive this weekend.

Around 9 inches of new snow fell along the Sierra Crest and about 6 inches fell in the Mount Rose area. Another 2-4 inches is forecasted to accumulate during today's scattered snow showers. That should bring overall storm totals to 11-13 inches for the Crest and 8-10 inches in the Mount Rose area. Even though the overall accumulation for this storm is not huge, the wind transport of the new snow has formed wind slabs on leeward slopes above treeline. The predominant winds were out of the southwest during the storm, but they have already started to move to the north and east this morning by shifting to the northwest at around 2am. These winds will scour the NW-N aspects that were previously loaded and redeposit this snow onto the NE-E-SE aspects. The wind slabs should continue to change in size and distribution throughout the day as the wind continues to shift.

As the new snow continues to be redistributed new weaknesses should form in the new snow layers. Layer bonding tests failed at the interface between the old snow surface and the new snow when moderate force was applied in the Mount Judah area near treeline yesterday. Loose snow sluffs that involved the new snow sluffing off the old snow surface were reported near Carson Pass yesterday as well. These observations and tests indicate that the bond between the bond between the new snow and old snow surface should also be suspect today.

Human triggered avalanche activity should still be possible today as new wind slabs form on top of the refrozen, old snow surface. Any avalanches that do occur today should occur due to failure at the interface with the old snow surface or failure at weaknesses formed during the storm. The possibility of triggering these slides will increase today as the wind continues to redistribute the snow. Directly windloaded and cross-loaded N-NE-E-SE aspects near and above treeline that are steeper than 35 degrees will be the most suspect. Only isolated areas of small wind slabs should develop below treeline. Human triggering of loose snow sluffs will also be possible today on any steep slopes. Natural avalanche activity is unlikely but not impossible today. Use clues like cornices, blowing snow, drifts, and ripples in the snow surface to determine what slopes have received wind loading. These are the slopes that will be the most worrisome and should warrant the most caution today.

The bottom line: The avalanche danger is MODERATE near and above treeline today. The most suspect areas will be on windloaded N-NE-E-SE aspects 35 degrees and steeper. Below treeline the avalanche danger should remain LOW with some isolated pockets of MODERATE avalanche danger on open, windloaded slopes 35 degrees and steeper. Both loose snow sluffs and slab avalanches are possible today. Use safe backcountry travel techniques, and re-assess snowpack conditions on a regular basis. Remember to be flexible and willing to change your plans when conditions change.

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.

Andy Anderson , Avalanche Forecaster
Today's Central Sierra Weather Observations:
0600 temperature at Sierra Crest (8,700 feet):
12 deg. F
Max. temperature at Sierra Crest past 24 hours:
27 deg. F
Average wind direction at Sierra Crest past 24 hours:
Southwest shifting to the northwest early this morning
Average wind speed at Sierra Crest past 24 hours:
35 mph
Maximum wind gust at Sierra Crest past 24 hours:
81 mph
New snow fall at 8,200 feet past 24 hours:
9
Total snow depth at 8,200 feet:
62 inches
Mountain Weather Forecast For Today:
Snow showers this morning becoming more isolated this afternoon. 2-4 inches of accumulation are possible.
Temperature forecast for 8,000 to 9,000 feet:
22 - 30 degrees F.
Ridgetop winds forecast for the Sierra Crest:
West at 20 to 30 mph with gusts to 50, shifting to the north in the afternoon.
Snowfall expected in the next 24 hours:
2-4 inches
2 Day Mountain Weather Forecast:

7000 to 8000 Feet:
Today, snow showers this morning becoming more isolated this afternoon. 1-2 inches of accumulation are possible. Daytime highs 25 to 33 degrees F. West winds at 15 to 20 mph shifting to the north this afternoon. Tonight, clear with overnight lows 16 to 22 degrees F. North winds at 10 to 15 mph shifting to the east after midnight. Tomorrow, partly cloudy with daytime highs around 47 degrees F.

Above 8000 Feet:
Today, snow showers this morning becoming more isolated this afternoon. 2-4 inches of accumulation are possible. Daytime highs 22 to 30 degrees F. West winds at 20 to 30 mph with gusts to 50, shifting to the north in the afternoon. Tonight, clear with overnight lows around 17 degrees F. Northeast winds at 10 to 20 mph with gusts to 45 mph. Tomorrow, partly cloudy with daytime highs 38 to 44 degrees F.

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.