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 March 12, 2008:


March 12, 2008 at 0:00 am

Forecast Discussion:


This advisory was posted on March 12, 2008 7:00 AM

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

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Today's Advisory:

The avalanche danger is LOW for all elevations and aspects. Some isolated pockets of MODERATE avalanche danger may develop on sun exposed slopes steeper than 37 degrees below treeline in response to daytime warming.

Cloud cover formed over the forecast area after midnight last night and temperatures dropped below freezing as a strong low pressure system in the Gulf of Alaska started to influence the forecast area. This system should bring more clouds, stronger winds, and cooler temperatures to the Sierra today. As this low pushes southward, it could bring some snow (3-6 inches above 8000 ft) to the area over the next 24 to 36 hours. A series of storms should follow this system making for a colder, wetter weekend.

Snowpack observations yesterday from across the forecast area continued to show 2 to 4 inches of soft corn snow forming by midday on southerly aspects. Spring sun and warm air temperatures melted some low elevation northerly aspects enough to create wet snow instabilities (mostly pinwheels and roller balls) yesterday. Overnight radiational cooling and air temperatures near or below freezing allowed snow that melted during the day yesterday to refreeze and gain strength. Upper elevation northerly aspects still hold a mix of wind packed surfaces, crusts, and very small pockets of unconsolidated snow.

Today, a more robust overnight refreeze due to cooler temperatures and radiational cooling, the extended duration of this melt/freeze cycle, more widespread cloud cover, and cooler temperatures should help prevent wet snow instabilities from becoming large and widespread. Any wet snow instabilities that do form should be limited to areas below treeline that see enough sunshine and warm air temperatures to allow free water to form in the snowpack due to melting. This free water will weaken the snowpack and human triggerable wet snow instabilities could form on these isolated slopes. Natural avalanches are unlikely today. The avalanche danger should increase over the next few days as new snow and wind loading affects the forecast area.

The bottom line: The avalanche danger is LOW for all elevations and aspects. Some isolated pockets of MODERATE avalanche danger may develop on sun exposed slopes steeper than 37 degrees below treeline in response to daytime warming.
Public donations to the avalanche center this season are below our fundraising goal. We are going to raffle a beacon, shovel, probe, and backpack package as a way give back to those who donate $100 or more before March 30th. For more information on the raffle and amount of donations received click here.

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: 47 deg. F.
Average wind direction at Sierra Crest past 24 hours: Southwest
Average wind speed at Sierra Crest past 24 hours: 15 mph.
Maximum wind gust at Sierra Crest past 24 hours: 35 mph
New snowfall at 8,200 feet past 24 hours: 0 inches
Total snow depth at 8,200 feet: 79 inches
Mountain Weather Forecast For Today:
Mostly cloudy and cooler.
Temperature forecast for 8,000 to 9,000 feet: 36 to 42 deg. F
Ridgetop winds forecast for the Sierra Crest: West at 15 to 25 mph with gusts to 40 mph increasing to 20 to 35 mph with gusts to 60 mph this afternoon.
Snowfall expected in the next 24 hours: 3-5 inches
2 Day Mountain Weather Forecast:

7000 to 8000 Feet:
Today, mostly cloudy skies with daytime highs 43 to 49 deg. F. West winds at 10 to 15 mph with gusts to 25 mph increasing to 15 to 25 mph with gusts to 35 mph in the afternoon.

Tonight, mostly cloudy skies with snow showers. Accumulations of up to 2 inches. Overnight lows 30 to 35 deg. F. Southwest winds at 15 to 30 mph with gusts to 45 mph.

For Thursday, mostly cloudy skies with a chance of snow. Accumulations of up to 1 inch. Daytime highs around 32 deg. F. Southwest winds at 15 to 25 mph with gusts to 40 mph increasing to 20 to 30 mph with gusts to 50 mph in the afternoon.

Above 8000 Feet:
Today, mostly cloudy skies with daytime highs 36 to 42 deg. F. West winds at 15 to 25 mph with gusts to 40 mph increasing to 20 to 30 mph with gusts to 50 mph in the afternoon.

Tonight, mostly cloudy skies with snow showers. Accumulations of 2 to 4 inches. Overnight lows 30 to 35 deg. F. West winds at 25 to 40 mph with gusts to 65 mph.

For Thursday, mostly cloudy skies with a chance of snow. Accumulations of up to 1 inch. Daytime highs 30 to 35 deg. F then dropping into the 20's by the afternoon. Southwest winds at 30 to 40 mph with gusts to 70 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:

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

For 8000-9000 ft:

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