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 Sunday, January 14, 2007 at 6:33 am

Cold arctic air remains firmly in place across the forecast area. A weak and dry weather disturbance is passing over the forecast area this morning. Mid level cloud cover associated with this system kept overnight temperatures about 10 degrees warmer than Friday night. Some light upslope snowfall is possible for the eastern half of the forecast area this afternoon, as northeasterly winds fill in behind the passage of the current weather system.

Moderate easterly winds yesterday morning continued to transport snow and create pockets of very small wind slab. These slabs have formed in lee and cross loaded areas on a variety of aspects near and above treeline. These small slabs may fail 2-3 inches below the snow surface today, but do not pose a significant threat to backcountry travelers. These slabs are very small in size and are not expected to propagate over any significant distance. Cold air temperatures continue to penetrate into the upper snowpack, creating the proper vapor pressure to fuel the near surface faceting process. Temperature gradients of 3 to 5 degrees C. per 10cm of snowpack height were observed yesterday both along the Sierra Crest and in the Mount Rose area. This is a very strong temperature gradient, uncommon in our snowpack. Temperature gradients that are strong enough to introduce a significant pressure gradient in our snowpack are typically slightly less than then 1 degree C. per 10 cm. With the current temperature gradient, faceting will continue to occur very rapidly. In the short term, this will keep surface snow unconsolidated in near and below treeline areas that are void of hard slabs. In the long term, faceting will weaken the upper snowpack at all elevations. This creates the potential for deeper snowpack instability, especially if the next large storm arrives prior to a period of warm weather.

Snow surface conditions remain variable by aspect and elevation. Sun and warm temperatures prior to the current cold snap left melt-freeze crust in sun exposed areas on SE-S-SW aspects, especially below 8,500'. NW-N-NE aspects have well defined stable hard slabs above treeline and lingering areas of nice unconsolidated snow below treeline in wind protected areas. On the E and W aspects, expect to find highly mixed snow surface conditions ranging from bare ground, crust, ice, and hard slab, to isolated pockets of unconsolidated snow.

Avalanche danger is LOW for all elevations and aspects.

Brandon Schwartz, Avalanche Forecaster

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Today's Central Sierra Weather Observations:
0600 temperature at Sierra Crest (8,700 feet): 8 deg. F
Max. temperature at Sierra Crest past 24 hours: 14 deg. F
Average wind direction at Sierra Crest past 24 hours: Easterly
Average wind speed at Sierra Crest past 24 hours: 22 mph
Maximum wind gust at Sierra Crest past 24 hours: 73 mph
New snow fall at 8,200 feet past 24 hours: 0 inches
Total snow depth at 8,200 feet: 40 inches

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Mountain Weather Forecast For Today:
Partly cloudy skies with a slight chance of snow showers
Temperature forecast for 8,000 to 9,000 feet: 13 - 18 deg. F
Ridgetop winds forecast for the Sierra Crest: Northeasterly 20 - 30 mph, G50 mph
Snowfall expected in the next 24 hours: 0 - 1 inch

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2 Day Mountain Weather Forecast:
7000 to 8000 Feet
Today, partly cloudy skies with a slight chance of snow showers for the eastern half of the forecast area this afternoon. Daytime highs 20 to 25 degrees F. Northeast winds 10 to 20 mph. Overnight, clear skies with lows 10 to 15 degrees F. East winds at 10 to 15 mph gusting to 25 mph. Monday will be sunny with daytime highs 28 to 33 degrees F. Northeast winds at 10 to 20 mph, diminishing in the afternoon are expected.

Above 8000 Feet
Today, partly cloudy skies with a slight chance of snow showers for the eastern half of the forecast area this afternoon. Daytime highs 13 to 18 degrees F. Northeast winds 20 to 30 mph gusting to 50 mph in the afternoon. Overnight, clear skies with lows 12 to 18 degrees F. East winds at 20 to 30 mph gusting to 50 mph. Monday will be sunny with daytime highs 23 to 28 degrees F. Northeast winds at 20 to 30 mph are expected to shift to east winds at 15 to 25 mph in the afternoon.

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