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 Wednesday, December 27, 2006 at 7:06 am

The winter storm warning is still in effect until 4pm today for the Tahoe area. Overnight the southwest winds continued to rage. They are started to calm down this morning, but they will still be strong today. The snow and rain that was forecasted for yesterday was only intermittent. It really started snowing last night. Along the crest we received 7-12 inches, and in the Rose area we got about 10 inches. Snow densities range from 12-17%. This storm will taper off this afternoon and usher in a period of cold clear weather. The winds are forecasted to shift to the north and east tonight.

The southwest wind has deposited significant windslabs on NW-N-NE aspects at all elevations. The high wind speeds were able to transport snow farther than usual and caused windslabs to form downhill from ridge lines and inside the trees in some areas. The E-SE slopes have been crossloaded with windslabs building out from the sides of those aspects rather than down from the top. Windslabs will be present in some less obvious places, so be alert for any signs of windloading and watch out for that terrain. On the exposed slopes these windslabs are sitting on a smooth crust. In the more protected areas the windslabs were deposited on top of the snow from our last storm which is on top of a crust. Yesterday some easy shear failures and moderate compression failures between the both of these crusts and the small windslabs that were starting to form were observed. These slabs grew overnight and will become more widespread and thicker as we get more snow throughout the day. As the slabs grow, they will put more strain on the interface between the crust and the windslab, and that interface will get closer to its failure point. A skier, snowboarder, or snowmobiler could be all that is needed to trigger an avalanche.

Today human triggered avalanches will be probable on any steep windloaded slopes. Any avalanches that are triggered will likely be those newly formed windslabs failing on weaknesses in the storm snow and stepping down to the crust layers.

Near and above treeline, avalanche danger is CONSIDERABLE. Below treeline, avalanche danger is CONSIDERABLE. Avalanche activity will be most likely on recently wind loaded NW-N-NE-E aspects 33 degrees and steeper.

Andy Anderson , Avalanche Forecaster
Today's Central Sierra Weather Observations:
0600 temperature at Sierra Crest (8,700 feet):
22 deg. F
Max. temperature at Sierra Crest past 24 hours:
31 deg. F
Average wind direction at Sierra Crest past 24 hours:
southwest
Average wind speed at Sierra Crest past 24 hours:
65 mph
Maximum wind gust at Sierra Crest past 24 hours:
167 mph
New snow fall at 8,200 feet past 24 hours:
7 inches
Total snow depth at 8,200 feet:
37 inches
Mountain Weather Forecast For Today:
Snow showers with accumulations of up to 12 ". The snow will taper off starting late this afternoon.
Temperature forecast for 8,000 to 9,000 feet:
27 deg. F
Ridgetop winds forecast for the Sierra Crest:
southwesterly 50-65 mph, G 90 mph shifting to the northwest at 20-30 mph this afternoon.
Snowfall expected in the next 24 hours:
12 inches
2 Day Mountain Weather Forecast:

7000 to 8000 Feet
For today, snow showers with up to 10" of snow accumulating. Winds out of the southwest at 30 to 45 mph with gusts to 55 mph shifting to the northwest at 15-25 mph this afternoon. Overnight mostly cloudy with a few snow showers. Lows 5 to 11 degrees F. North winds at 20-30 mph shifting to northeast winds at 30 to 40 mph after midnight. Wednesday partly cloudy. Daytime highs around 28 degrees F. Northeast winds 30 to 45 mph.

Above 8000 Feet
For today, snow showers with up to 12" of snow accumulating. Winds out of the southwest at 50 to 65 mph with gusts to 90 mph shifting to the northwest at 20-30 mph this afternoon. Overnight mostly cloudy with a few snow showers. Lows 4 to 10 degrees F. North winds at 25-35 mph shifting to northeast winds at 50 to 70 mph after midnight. Wednesday partly cloudy. Daytime highs around 29 degrees F. Northeast winds 50 to 70 mph.

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:
	Wednesday:	Wednesday Night:	Thursday:
Weather:
Temperatures:	deg. F.	deg. F.	deg. F.
Wind direction:
Wind speed:
Expected snowfall:	O in.	O in.	O in.
For 8000-9000 ft:
	Wednesday:	Wednesday Night:	Thursday:
Weather:
Temperatures:	deg. F.	deg. F.	deg. F.
Wind direction:
Wind speed:
Expected snowfall:	O in.	O in.	O in.