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 3, 2008 7:00 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 HIGH on NW-N-NE-E-SE aspects, 35 degrees and steeper. Below treeline, avalanche danger is MODERATE with pockets of CONSIDERABLE danger in open areas, 37 degrees and steeper.

A strong Pacific storm is currently affecting the forecast area. Significant snowfall began late yesterday afternoon and continues this morning. Ski area snow study plots and remote sensors are reporting new snow amounts of 16 to 22 inches across the forecast area this morning. The snow study plot at Mt. Rose ski area is reporting and overall new snow density of 13%. Heavy snowfall is expected to continue through 10 am with another 6 to 10 inches expected. Snow shower activity is forecast to continue into Monday. Mountain top air temperatures warmed a few degrees during the first 3 to 4 hours of heavy snowfall last night. Air temperatures began to fall between 4 and 6 am this morning and are expected to become colder as the day progresses. Ridgetop winds have been strong from the southwest and are shifting to west this morning.

The existing snowpack is in good condition to handle the amount of new snow loading created by the current storm system. Snowpack observations made over the past several days on Castle Peak, Mt. Lincoln, Silver Peak, in Blackwood Canyon, on Hidden Peak, Waterhouse Peak, and Tamarack Peak have shown good layer bond strength within the top 4 to 5 feet of the snowpack. Avalanche activity that fails below the height of the old/new snow interface is not expected at this time.

Today, avalanche activity is expected to occur within the new snow or just above the old/new snow interface. Warming air temperatures during the early part of the storm are expected to have placed higher density snow on top of lower density snow. Snowpack failure that occurs today at this interface has the potential to occur several feet deep in wind loaded areas. Snowpack failure that occurs higher within the new snow still has significant destructive potential with crown height of well over 1 foot expected. Early reports indicate that natural avalanche activity overnight ran down onto the Alpine Meadows road, releasing from the cross loaded SE aspect gullies above. Continued snowfall and moderate west winds will cause wind loading to continue through the day today. As winds shift to the west and continue to decrease this morning, loading will begin to occur higher in avalanche start zones, increasing the size of slabs that formed further down slope during the overnight hours.

Natural and human triggered avalanche activity is likely today on directly wind loaded N-NE-E aspects and on cross loaded NW and SE aspects on steep slopes in near and above treeline areas. Below treeline, human triggered avalanches are possible to probable while natural avalanches are possible is steep open areas, especially where wind has aided in slab formation.

The bottom line: Near and above treeline, avalanche danger is HIGH on NW-N-NE-E-SE aspects, 35 degrees and steeper. Below treeline, avalanche danger is MODERATE with pockets of CONSIDERABLE danger in open areas, 37 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): 17 deg. F
Max. temperature at Sierra Crest past 24 hours: 19 deg. F
Average wind direction at Sierra Crest past 24 hours: Southwest
Average wind speed at Sierra Crest past 24 hours: 68 mph
Maximum wind gust at Sierra Crest past 24 hours: 144 mph
New snow fall at 8,200 feet past 24 hours: 16 to 22 inches
Total snow depth at 8,200 feet: 85 to 95 inches

Mountain Weather Forecast For Today:
Cloudy skies with heavy snowfall in the morning, snow showers in the afternoon.
Temperature forecast for 8,000 to 9,000 feet: 14 to 19 deg. F
Ridgetop winds forecast for the Sierra Crest: West at 45 to 65 mph with gusts to 100 mph, decreasing to 20 to 35 mph with gusts to 60 mph in the afternoon.
Snowfall expected in the next 24 hours: 6 to 10 inches

2 Day Mountain Weather Forecast:

7000 to 8000 Feet:
Today, cloudy skies with heavy snowfall in the morning. Snow showers in the afternoon. Snow accumulation 4 to 8 inches. Daytime highs 22 to 26 deg. F. in the morning, falling to the teens by the afternoon. Southwest winds at 25 to 40 mph, gusting to 60 mph. Winds shifting to west and decreasing to 15 to 25 mph with gusts to 35 mph in the afternoon.

Tonight, cloudy with snow showers in the evening, then mostly cloudy with isolated snow showers after midnight. Overnight lows around 10 deg. F. Northwest winds at 10 to 20 mph with gusts to 30 mph.

For Monday, mostly cloudy skies with daytime highs 25 to 30 deg. F. North winds at 10 to 20 mph with gusts to 30 mph.

Above 8000 Feet:
Today, cloudy skies with heavy snowfall in the morning. Snow showers in the afternoon. Snow accumulation 6 to 10 inches. Daytime highs 19 to 25 deg. F. in the morning, falling to the teens by the afternoon. Southwest winds at 35 to 50 mph with gusts to 100 mph. Winds shifting to west and decreasing to 20 to 35 mph with gusts to 60 mph by the afternoon.

Tonight, cloudy with snow showers in the evening, then mostly cloudy with isolated snow showers after midnight. Overnight lows 5 to 10 deg. F. Northwest winds at 15 to 25 mph with gusts to 40 mph.

For Monday, mostly cloudy skies with daytime highs 18 to 25 deg. F. Northeast winds at 10 to 15 mph increasing to 20 to 30 mph with gusts to 60 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.