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 December 29, 2007 6:55 AM
Click here for a detailed map of the SAC forecast area

low avalanche danger
Today's Advisory:

Avalanche danger is LOW for all elevations and aspects. Normal caution is advised.

After a brief period of freezing rain along the crest yesterday, the precipitation turned back to snow with less than an inch accumulating across most of the forecast area. The Mount Rose area picked up the most snow with about 3 inches of accumulation in the last 24 hrs. The forecast calls for some light snow showers through the day with accumulations reaching up to 2 inches above 7000'. A ridge of high pressure should bring some warmer air into the forecast area today before a strong cold front moves into the Pacific Northwest. This front should bring cold northeasterly flow to the forecast area as it moves east later this weekend and early next week. The southwest winds have already picked up into the 40s along the crest and should increase through tonight. By tomorrow these winds should start shifting to more to the west and north.

Yesterday the temperatures stayed cold enough that when the rain got to the snow surface it immediately froze and formed a thin, fragile rain crust on top of the recent cold, dry snow. Observers reported this crust reaching all the way up to 9000' in the southern part of the forecast area. The interface between this crust and the layers below easily failed during layer bonding tests yesterday. Luckily, there is only .5 to 1 inch of snow sitting on top of this crust, therefore one of the key avalanche ingredients is missing: the slab. As the winds transport snow today some tiny cornices and very small pillows may form on top of this crust in the most heavily wind loaded areas above treeline. These potentially unstable features are expected to be very small and not present much hazard to backcountry travelers. Observations and snow pit data indicate that facets continue to form in the lower layers of the the snowpack. However layer bonding tests continue to show the snowpack gaining strength within layers and between layers in the lower part of the current snowpack.

A mix of snow surface conditions exists on various aspects and at different elevations throughout the area. Along the Sierra Crest 1 to 2 inches of new snow on top of the thin, zipper crust formed by the rain yesterday will be the most common snow surface today. On the windward slopes expect heavy scouring and a shallow snowpack. On the south and west aspects and on most aspects below 7,000', expect to find melt-freeze crusts and sun crusts below the rain crust. The sheltered north and east aspects still have unconsolidated snow below the rain crust and still provide some fun riding.

The bottom line: Avalanche danger is LOW for all elevations and aspects. Normal caution is advised.

Please send us your snow, weather, and avalanche observations by clicking the submit observations link on our contact page.

Andy Anderson, Avalanche Forecaster

Today's Central Sierra Weather Observations:
0600 temperature at Sierra Crest (8,700 feet): 20 deg. F
Max. temperature at Sierra Crest past 24 hours: 20 deg. F
Average wind direction at Sierra Crest past 24 hours: Southwest
Average wind speed at Sierra Crest past 24 hours: 35 mph
Maximum wind gust at Sierra Crest past 24 hours: 67 mph
New snow fall at 8,200 feet past 24 hours: 1 to 3 inches
Total snow depth at 8,200 feet: 31 inches
Mountain Weather Forecast For Today:
Cloudy skies with snow showers in the morning.
Temperature forecast for 8,000 to 9,000 feet: 29 to 33 deg. F
Ridgetop winds forecast for the Sierra Crest: West at 30 to 45 mph with gusts to 80 mph.
Snowfall expected in the next 24 hours: up to 2 inches
2 Day Mountain Weather Forecast:

7000 to 8000 Feet:
Today, cloudy skies with snow showers in the morning. Snow accumulation up to 2 inches. Daytime highs 31 to 36 deg. F. Southwest winds at 20 to 35 mph with gusts to 55 mph.

Tonight, mostly cloudy skies with scattered snow showers. Overnight lows 25 to 30 deg. F. West winds at 25 to 35 mph with gusts to 60 mph.

For Sunday, mostly cloudy skies with a slight chance of scattered snow showers. Daytime highs 28 to 33 deg. F. West winds at 15 to 25 mph with gusts to 35 mph.

Above 8000 Feet:
Today, cloudy skies with snow showers in the morning. Snow accumulation up to 2 inches. Daytime highs 29 to 33 deg. F. West winds at 30 to 45 mph with gusts to 80 mph.

Tonight, mostly cloudy skies with scattered snow showers. Overnight lows 23 to 27 deg. F. West winds at 40 to 55 mph with gusts to 85 mph.

For Sunday, mostly cloudy skies with a slight chance of scattered snow showers. Daytime highs in the 20's. West winds at 20 to 30 mph with gusts to 55 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:
	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.