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 Avalanche Advisory was published on January 22, 2008:


January 22, 2008 at 1:00 am

Forecast Discussion:


This advisory was posted on January 22, 2008 6:58 AM
Click here for a detailed map of the SAC forecast area

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Today's Advisory:

In most areas, avalanche danger is LOW for all elevations and aspects. Very isolated pockets of MODERATE avalanche danger linger near and above treeline in recently wind loaded areas, 37 degrees and steeper. Below treeline, very isolated pockets of MODERATE avalanche danger exist in open areas 40 degrees and steeper where loose snow avalanche activity remains possible.

Snow showers have affected the forecast area off and on for the past 36 hours. Snow shower bands have been narrow, with a significant variance in the amount of accumulation at various locations just a few miles apart. New snow totals range from 8 to 16 inches along the northern Sierra Crest and around 8 to 10 inches along the Sierra Crest in the southern portion of the forecast area. New snow amounts in the Mount Rose area are around 7 to 8 inches. Ridgetop winds have shifted from southwest to east during the overnight hours.

Yesterday, isolated areas of human triggered snowpack instability were reported above Negro Canyon (Donner Summit area) on a 40 degree north aspect at 7,600' in wind loaded pockets up to 2 feet deep above treeline. Shooting cracks up to 5 feet long were reported within small slab features directly below cornice formations on steep test slopes. Snowpack failure occurred within the new snow in this area. At the top of Hidden Peak (West Shore Tahoe area), 1 foot of new snow was observed with minimal wind loading and no slab formation on NE-E aspects along the ridgeline at 9,100'. Isolated pockets of human triggered sluff activity were observed below treeline at 7,600' on a 40 degree convex micro feature. New snow failed on top of a hard frozen crust in this location. On Slide Mountain (Mount Rose area), very shallow soft slabs 2 to 3 inches deep, failing at the old/new snow interface were human triggered around mid day on steep N-NE aspects with fracture propagation up to 60' reported.

Up to 3 inches of new snow fell prior to midnight last night with ridgetop winds shifting to the east. Less snowpack instability is expected today due to the small amount of new snow received in the past 12 hours and the redistribution of snow by east and southeast winds today. Due to the low density (around 4-5%) of the recent snow, it will be easily redistributed by shifting winds today. Some pockets of small and shallow slabs will linger today in recently wind loaded areas. Human triggering of these small slabs remains possible in very isolated areas on steep and wind loaded slopes. Below treeline, the possibility of loose snow avalanche activity (sluffs) remains possible in steep open areas.

The bottom line: In most areas, avalanche danger is LOW for all elevations and aspects. Very isolated pockets of MODERATE avalanche danger linger near and above treeline in recently wind loaded areas, 37 degrees and steeper. Below treeline, very isolated pockets of MODERATE avalanche danger exist in open areas 40 degrees and steeper where loose snow avalanche activity remains possible.

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): 12 deg. F
Max. temperature at Sierra Crest past 24 hours: 17 deg. F
Average wind direction at Sierra Crest past 24 hours: Southwest shifting to east
Average wind speed at Sierra Crest past 24 hours: 25 mph
Maximum wind gust at Sierra Crest past 24 hours: 60 mph
New snow fall at 8,200 feet past 24 hours: 4 to 6 inches
Total snow depth at 8,200 feet: 66 inches

Mountain Weather Forecast For Today:
Cloudy skies with scattered snow showers.
Temperature forecast for 8,000 to 9,000 feet: 15 to 21 deg. F
Ridgetop winds forecast for the Sierra Crest: East at 15 to 25 mph with gusts to 45 mph, shifting to southeast by early afternoon.
Snowfall expected in the next 24 hours: 2 to 4 inches

2 Day Mountain Weather Forecast:

7000 to 8000 Feet:
Today, cloudy skies with isolated snow showers. Snow accumulation up to 2 inches. Daytime highs around 23 deg. F. East winds at 10 to 15 mph with gusts to 30 mph in the morning.

Tonight, cloudy skies with scattered snow showers. Snow accumulation up to 1 inch. Overnight lows around 14 deg. F. East winds at 10 mph.

For Wednesday, cloudy skies with scattered snow showers. Snow accumulation up to 1 inch. Daytime highs around 26 deg. F. East winds at 10 to 20 mph.

Above 8000 Feet:
Today, cloudy skies with isolated snow showers. Snow accumulation up to 3 inches. Daytime highs around 20 deg. F. East winds at 15 to 25 mph with gusts to 45 mph, shifting to southeast with gusts to 40 mph by early afternoon.

Tonight, cloudy skies with scattered snow showers. Snow accumulation up to 1 inch. Overnight lows around 12 deg. F. Southeast winds at 10 to 15 mph with gusts to 30 mph.

For Wednesday, cloudy skies with scattered snow showers. Snow accumulation up to 2 inches. Daytime highs around 22 deg. F. Southeast winds at 15 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:

  Tuesday: Tuesday Night: Wednesday:
Weather:
Temperatures: deg. F. deg. F. deg. F.
Wind direction:
Wind speed:
Expected snowfall: O in. O in. O in.

For 8000-9000 ft:

  Tuesday: Tuesday Night: Wednesday:
Weather:
Temperatures: deg. F. deg. F. deg. F.
Wind direction:
Wind speed:
Expected snowfall: O in. O in. O in.