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 February 17, 2008 7:00 AM
Click here for a detailed map of the SAC forecast area

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Today's Advisory:

This morning, avalanche danger is LOW for all elevations and aspects. Areas of MODERATE avalanche danger will develop on SE-S-SW aspects, 37 degrees and steeper in response to daytime warming.

The forecast calls for more sun and slightly warmer temperatures today as the high pressure ridge remains over the area. Yesterday temperatures reached the mid to upper 40's above 8000' across the forecast area before dropping back below freezing overnight. This morning the remote sensors show air temperatures above 8000' still below freezing and slightly lower temperatures at the lower elevations due to an inversion.

Yesterday only the top 3 to 5 inches of snow on sun exposed southerly aspects softened due to daytime warming. Below this surface layer of melt/freeze snow, observations show a strong, well bonded snowpack. On the northerly aspects snow surfaces remained cold and observations continue to show a strengthening snowpack. The snow surfaces that softened yesterday quickly refroze overnight due to radiational cooling and below freezing air temperatures. Clear skies, warmer air temperatures,and light winds should create free water in the upper part of the snowpack today on sun exposed aspects. As this melt water dissolves the bonds between the refrozen snow grains in the upper snowpack areas of wet surface snow instability may form on steep SE-S-SW aspects. Less solar radiation striking the snow surface due to short winter days and low sun angles leads to less rapid melting of the surface snow and less melt water infiltrating the snowpack. Melt water pathways that drain this water through the snowpack have also formed during this prolonged melt/freeze cycle. These two things should help keep large, deep wet snow instabilities from forming. Today snow surface conditions will continue to be a mix of wind scoured and wind affected surfaces on northerly aspects above treeline; pockets of soft snow on shaded, wind sheltered northerly aspects below treeline; and melt/freeze (corn/crusts) snow conditions on the southerly aspects.

Wet snow avalanche activity that fails in response to human triggering will become possible today on steep SE-S-SW aspects as daytime warming occurs. Most of this activity should be in the form of wet surface instabilities like pinwheels and point release avalanches. Wet slab avalanche activity is unlikely but it is not impossible today. Simple clues and tests like pinwheels, roller balls, and how deep boots penetrate into wet snow (ankle deep or deeper is a bad sign) are good indicators of when it is time to find more frozen slopes. Natural avalanche activity is unlikely today.

The bottom line: This morning, avalanche danger is LOW for all elevations and aspects. Areas of MODERATE avalanche danger will develop on SE-S-SW aspects, 37 degrees and steeper in response to daytime warming.

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): 30 deg. F
Max. temperature at Sierra Crest past 24 hours: 42 to 47 deg. F.
Average wind direction at Sierra Crest past 24 hours: Northeast
Average wind speed at Sierra Crest past 24 hours: 10 mph
Maximum wind gust at Sierra Crest past 24 hours: 27 mph
New snow fall at 8,200 feet past 24 hours: 0 inches
Total snow depth at 8,200 feet: 80 inches
Mountain Weather Forecast For Today:
Sunny and warm.
Temperature forecast for 8,000 to 9,000 feet: around 47 deg. F
Ridgetop winds forecast for the Sierra Crest: North at 10 mph
Snowfall expected in the next 24 hours: 0 inches
2 Day Mountain Weather Forecast:

7000 to 8000 Feet:
Today, sunny skies with daytime highs around 51 deg. F. Light winds in the morning shifting to the northeast and increasing to 10 mph in the afternoon.

Tonight, clear skies with overnight lows 21 to 31 deg. F. Light winds in the evening shifting to the east and increasing to 10 mph overnight.

For Monday, partly cloudy with daytime highs around 50 deg. F. Winds out of the southeast at 10 mph.

Above 8000 Feet:
Today, sunny skies with daytime highs around 47 deg. F. Winds out of the north at 10 mph.

Tonight, clear skies with overnight lows 26 to 32 deg. F. Winds out of the east at 10 to 15 mph.

For Monday, partly cloudy with daytime highs 41 to 47 deg. F. Winds out of the south at 10 to 15 mph with gusts to 25 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:
	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.