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 January 20, 2008 6:52 AM
Click here for a detailed map of the SAC forecast area

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Today's Advisory:

Avalanche danger is LOW for all elevations and aspects. Normal caution is advised. After the onset of snowfall, avalanche danger is expected to increasing during the late afternoon and evening hours.

A series of weak weather disturbances are approaching the forecast area at this time. Ridgetop winds have shifted to the southwest and steadily increased in speed over the past 24 hours. Winds are expected to reach maximum speed for this event during the morning hours today. Winds are then expected to decrease during the afternoon hours and overnight into Monday. Snowfall is expected to start in northern portion of the forecast area late this afternoon, spreading to the southern portion during the evening hours. A quick 2 to 5 inches of new snow is expected before snowfall tapers off around midnight. Cold air temperatures are expected with the passage of the first weather system.

Surface hoar crystals that were observed at many locations around the forecast area have mostly been melted by warm afternoon air temperatures over the past two days. A few very isolated patches of surface hoar may remain on steep and shaded north aspect micro features on protected slopes above 7,000'. Due to the very small snow surface area covered and very isolated distribution of any remaining surface hoar, it is not expected to play a significant role in future snowpack instability.

Near surface faceted snow crystals have developed below surface crusts in many areas on NW-N-NE-E aspects over the past week and are continuing to loose strength. Layer bonding tests performed yesterday on Castle Peak (Donner Summit area) and on Jake's Peak (West Shore Tahoe area) are showing moderate to hard force failure on these crystals within the upper 4 to 8 inches of the snowpack where no failure was observed one week ago. This weakness has not been reported in the Mount Rose area. This layer of near surface faceted crystals is in fair condition to handle new snow loading at this time. Layers deeper within the snowpack remain very strong and are in excellent condition to handle new snow loading.

The bottom line: Avalanche danger is LOW for all elevations and aspects. Normal caution is advised. After the onset of snowfall, avalanche danger is expected to increasing during the late afternoon and evening hours.
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): 18 deg. F
Max. temperature at Sierra Crest past 24 hours: 32 deg. F
Average wind direction at Sierra Crest past 24 hours: Southwest
Average wind speed at Sierra Crest past 24 hours: 36 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: 53 inches

Mountain Weather Forecast For Today:
Partly cloudy to cloudy skies with isolated snow showers in the morning. Snow likely in the afternoon.
Temperature forecast for 8,000 to 9,000 feet: 26 to 29 deg. F
Ridgetop winds forecast for the Sierra Crest: Southwest at 30 to 40 mph with gusts to 70 mph in the morning, decreasing to 20 to 30 mph with gusts to 60 mph in the afternoon.
Snowfall expected in the next 24 hours: 2 to 6 inches

2 Day Mountain Weather Forecast:

7000 to 8000 Feet:
Today, partly cloudy skies in the morning with isolated snow showers. Increasing clouds with snow likely in the afternoon. Snow accumulation up to 1 inch. Daytime highs around 31 deg. F. Southwest winds at 15 to 25 mph with gusts to 35 mph.

Tonight, cloudy skies with snow in the evening, then scattered snow showers after midnight. Snow accumulation 2 to 5 inches. Overnight lows 14 to 20 deg. F. West winds at 10 to 15 mph with gusts to 25 mph in the evening.

For Monday, cloudy skies with a chance of snow showers in the morning, then snow likely in the afternoon. Snow accumulation 1 to 3 inches. Daytime highs around 20 deg. F. Southwest winds at 10 to 20 mph with gusts to 30 mph.

Above 8000 Feet:
Today, partly cloudy skies in the morning with isolated snow showers. Increasing clouds with snow likely in the afternoon. Snow accumulation up to 1 inch. Daytime highs around 29 deg. F. Southwest winds at 20 to 30 mph with gusts to 60 mph.

Tonight, cloudy skies with snow in the evening, then scattered snow showers after midnight. Snow accumulation 2 to 5 inches. Overnight lows 11 to 17 deg. F. West winds at 10 to 20 mph with gusts to 40 mph, decreasing to 30 mph after midnight.

For Monday, cloudy skies with a chance of snow showers in the morning, then snow likely in the afternoon. Snow accumulation 2 to 4 inches. Daytime highs 13 to 19 deg. F. Southwest winds at 10 to 15 mph, increasing to 15 to 25 mph with gusts to 35 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.