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 22, 2007 6:51 AM
Click here for a detailed map of the SAC forecast area

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Today's Advisory:
Near and above treeline, avalanche danger is MODERATE with pockets of CONSIDERABLE danger on N-NE-E aspects, 35 degrees and steeper. Below treeline, avalanche danger is MODERATE in open areas, 35 degrees and steeper.

As a storm system passes to the north of our area today, increasing cloud cover will occur over the forecast area. A temperature inversion is in place this morning causing cold temperatures at the valley floor and warmer air temperatures at the higher elevations. At the 8,000 foot level, air temperatures have warmed rapidly overnight to near and above freezing in some areas. East winds slowed down late yesterday and are shifting to the north and become light this morning.

Yesterday, collapsing and whumphing were again observed above and below treeline around Incline Lake and the upper portion of the Third Creek drainage in the Mount Rose area. The persistent failure layer remains the interface between the recent storm snow and the faceted basal layer. These obvious signs of instability are less prevalent along the Sierra Crest with no recent backcountry avalanche activity reported. However, snowpit observations have revealed a shallow and relatively weak early season snowpack structure along the Sierra Crest both north of Lake Tahoe and south near the Bear Valley (Ebbets Pass) area.

Recent east winds removed some snow from avalanche start zones on N-NE-E aspects. What remains are stiff slabs that are more likely to fail once a person is already committed on a slope rather than when they first enter a slope. This reduces the potential to escape off the edge of an avalanche and increases the potential for burial. These stiffer slabs have the potential to act as hard slab avalanches and be more destructive than the soft slabs that were observed over the past several days.
Rapid air temperature warming at the upper elevations is cause for concern today. As temperatures rapidly approach and rise above freezing, the amount of stress on the snowpack will increase. The chances of human triggered and natural avalanche activity will increase today. Human triggered avalanches are possible today in a variety of areas both above and below treeline. Some isolated areas where human triggered avalanches are probable and natural avalanches are possible are expected to form today on steep N-NE-E aspects where new snow sits on top of a layer of faceted snow crystals.

The bottom line: Near and above treeline, avalanche danger is MODERATE with pockets of CONSIDERABLE danger on N-NE-E aspects, 35 degrees and steeper. Below treeline, avalanche danger is MODERATE in open areas, 35 degrees and steeper.

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

Brandon Schwartz, Avalanche Forecaster

Today's Central Sierra Weather Observations:
0600 temperature at Sierra Crest (8,700 feet): 33 deg. F
Max. temperature at Sierra Crest past 24 hours: 33 deg. F
Average wind direction at Sierra Crest past 24 hours: East shifting to north
Average wind speed at Sierra Crest past 24 hours: 32 mph
Maximum wind gust at Sierra Crest past 24 hours: 67 mph
New snow fall at 8,200 feet past 24 hours: 0 inches
Total snow depth at 8,200 feet: 34 inches

Mountain Weather Forecast For Today:
Mostly cloudy skies.
Temperature forecast for 8,000 to 9,000 feet: 31 to 37 deg. F.
Ridgetop winds forecast for the Sierra Crest: North at 6 to 12 mph with gusts to 25 mph.
Snowfall expected in the next 24 hours: 0 inches

2 Day Mountain Weather Forecast:

7000 to 8000 Feet:
Today, mostly cloudy skies with daytime highs 32 to 38 deg. F. South winds at 10 mph.

Tonight, cloudy skies with overnight lows 17 to 22 deg. F. West winds at 10 to 15 mph with gusts to 25 mph.

For Sunday, mostly cloudy with daytime highs 35 to 40 deg. F. West winds at 10 to 15 mph.

Above 8000 Feet:
Today, mostly cloudy skies with daytime highs 31 to 37 deg. F. North winds at 6 to 12 mph with gusts to 25 mph.

Tonight, mostly cloudy skies with overnight lows 23 to 28 deg. F. Northwest winds at 15 to 25 mph with gust to 40 mph.

For Sunday, mostly cloudy with daytime highs 33 to 38 deg. F. Northwest winds at 15 to 25 mph with gust to 40 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.