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 April 18, 2008:


April 18, 2008 at 0:00 am

Forecast Discussion:


This advisory was posted on April 18, 2008 7:00 AM

A map of the SAC forecast area is available on our home page.

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Today's Advisory:

Avalanche danger is LOW for all elevations and aspects. Some small, isolated areas of MODERATE danger could develop on sun exposed SE-S-SW aspects steeper than 38 degrees due to daytime warming.

In the Mount Rose area and in some places along the Sierra Crest overnight temperatures fell below freezing. Other areas along the crest stayed just above freezing all night. Air temperatures should be slightly cooler today due to an approaching low pressure system and its associated cold front. This system also caused the winds to shift to the southwest and start increasing last night. This system should also start to push some clouds into the area today with mostly cloudy skies forecasted for Saturday. As the cold front passes through the forecast area air temperatures should cool dramatically leading to a chilly weekend.

Yesterday high temperatures reached the low 50's above 8000' and all aspects below 9500' experienced some melting. Observations on Mt. Tallac revealed that melt water has started to form channels in the snowpack on northerly aspects and that the melt water pathways on southerly aspects remain well established. The top 3 to 5 inches of surface snow softened on SE-S-SW aspects on the south side of Mt. Tallac by 1 pm, and observers reported good corn conditions forming by 10 am on the SE aspects. A few small human triggered wet snow sluffs that only ran 10 to 30 feet downhill occured on steep south facing slopes in this area yesterday around midday. The clear skies and overnight temperatures near and below freezing should have allowed another solid refreeze to occur in the snowpack across the forecast area last night.

Today, continued sunshine and warm air temperatures will cause the surface snow to soften and melt quickly on any sun exposed slopes. The most melting should occur on E-SE-S-SW-W aspects where some isolated areas of wet snow instability could develop. The the solid refreeze that adds strength to the snowpack and well established drainage channels that prevent the newly formed free water from pooling at a specific layer should keep these instabilities small and limited to human triggered point release sluffs. Large wet slab avalanche activity should remain unlikely but not impossible in areas where the snowpack sits on an impermeable ground surface like a granite slab. Natural avalanches are unlikely at this time.

The bottom line: Avalanche danger is LOW for all elevations and aspects. Some small, isolated areas of MODERATE danger could develop on sun exposed SE-S-SW aspects steeper than 38 degrees due to daytime warming.

Andy Anderson, Avalanche Forecaster

Today's Central Sierra Weather Observations:
0600 temperature at Sierra Crest (8,700 feet): 31 to 36 deg. F
Max. temperature at Sierra Crest past 24 hours: 50 to 56 deg. F.
Average wind direction at Sierra Crest past 24 hours: Southwest
Average wind speed at Sierra Crest past 24 hours: 25 mph
Maximum wind gust at Sierra Crest past 24 hours: 48 mph
New snowfall at 8,200 feet past 24 hours: 0 inches
Total snow depth at 8,200 feet: 64 inches
Mountain Weather Forecast For Today:
Sunny and warm with a few clouds developing during the day.
Temperature forecast for 8,000 to 9,000 feet: 46 to 52 deg. F
Ridgetop winds forecast for the Sierra Crest: Southwest 20 to 35 mph with gusts to 50 mph.
Snowfall expected in the next 24 hours: 0 inches
2 Day Mountain Weather Forecast:

7000 to 8000 Feet:

Today, sunny skies with a few clouds developing during the day. Daytime highs 52 to 58 deg. F. Southwest winds at 10 to 15 mph with gusts to 25 mph increasing to 15 to 25 mph with gusts to 40 mph this afternoon.

Tonight, partly cloudy skies with overnight lows around 31 deg. F. Southwest winds at 15 to 25 mph with gusts to 40 mph.

For Saturday, mostly cloudy skies with daytime highs 39 to 45 deg. F. Southwest winds at 20 to 35 mph with gusts to 50 mph.

Above 8000 Feet:

Today, sunny skies with a few clouds developing during the day. Daytime highs 46 to 52 deg. F. Southwest winds at 20 to 35 mph with gusts to 50 mph.

Tonight, partly cloudy skies with overnight lows 24 to 30 deg. F. Southwest winds at 20 to 30 mph with gusts to 50 mph shifting to the south and increasing to 25 to 40 mph with gusts to 60 mph after midnight.

For Saturday, mostly cloudy skies with daytime highs 32 to 40 deg. F. Southwest winds at 40 to 55 mph with gusts to 75 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:

  Friday: Friday Night: Saturday:
Weather:
Temperatures: deg. F. deg. F. deg. F.
Wind direction:
Wind speed:
Expected snowfall: O in. O in. O in.

For 8000-9000 ft:

  Friday: Friday Night: Saturday:
Weather:
Temperatures: deg. F. deg. F. deg. F.
Wind direction:
Wind speed:
Expected snowfall: O in. O in. O in.