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 February 13, 2007:

February 13, 2007 at 1:00 am

Forecast Discussion:

This advisory was posted on Tuesday, February 13th, 2007 at 7:00 am

The bottom line: Near and above treeline, avalanche danger is MODERATE on recently wind loaded NW-N-NE-E aspects 35 degrees and steeper. Below treeline, avalanche danger is LOW. Human triggered avalanches remain possible today. Natural avalanches are unlikely.

Low amounts of moisture continue to linger over the forecast area. This is expected to create similar conditions to yesterday with increasing cloud cover and another period of snow shower activity during the afternoon hours. Ridgetop winds are expected to shift from southwesterly to northerly by this afternoon.

Snow showers yesterday afternoon added an additional 1-2 inches of new snow on top of the storm snow from the past several days. Moderate to hard force shears were observed yesterday within the recent storm snow and at the base of the storm snow at the old snow interface. This was evident both along the Sierra Crest and in the Mount Rose area. Prominent shear location within the snowpack varies by location with no easily discernable pattern. Three different repeatable shear locations are apparent from various snowpack observations and observers. One shear is located within the storm snow just below the layer of wet snow that was deposited on top of drier snow during a period of rising snow levels that occurred Saturday night. Another consistent shear has been observed within the top foot of the storm snow on a layer of needle and rimed crystals. The third consistent shear has been observed at the interface between the old snow surface and the storm snow. Rarely are all three of these shears observed in the same snowpit, but these are the observed and reported failure layers for recent avalanche activity.

Yesterday, several human triggered slab avalanches occurred near and above treeline on recently wind loaded N-NE-E aspects. These events were reported in the Carson Pass area and in the Mount Rose area. The existing slabs have gained strength and were observed to fail after the passage of multiple skiers or with additional loading after the initial use of explosives.

Areas of snowpack instability will continue today on recently wind loaded NW-N-NE-E aspects, 35 degrees and steeper. Backcountry travelers should exercise caution as slabs may not fail until the passage of one or more individuals. Practice safe travel techniques by exposing only on person at a time to avalanche terrain, moving from one safe zone to the next. Keep this in mind during both uphill and downhill travel.

The bottom line: Near and above treeline, avalanche danger is MODERATE on recently wind loaded NW-N-NE-E aspects 35 degrees and steeper. Below treeline, avalanche danger is LOW. Human triggered avalanches remain possible today. Natural avalanches are unlikely.

At this time, we have not raised enough money to meet our operating budget for this year. If you use this service with any regularity and would like to continue to do so, please show your support for the Sierra Avalanche Center. You may make a tax deductible donation directly to us via Paypal or by sending a check to our address listed above, c/o the Truckee Ranger Station. A financial graph showing the current fundraising and budget numbers is available by clicking here. The financial support already received this winter from a variety of users is greatly appreciated.

Brandon Schwartz, Avalanche Forecaster

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Today's Central Sierra Weather Observations:
0600 temperature at Sierra Crest (8,700 feet): 19 deg. F
Max. temperature at Sierra Crest past 24 hours: 28 deg. F
Average wind direction at Sierra Crest past 24 hours: westsouthwesterly
Average wind speed at Sierra Crest past 24 hours: 20 mph
Maximum wind gust at Sierra Crest past 24 hours: 39 mph
New snow fall at 8,200 feet past 24 hours: 1 - 2 inches
Total snow depth at 8,200 feet: 59 inches

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Mountain Weather Forecast For Today:
Mostly cloudy skies with snow showers, most intense in the afternoon .
Temperature forecast for 8,000 to 9,000 feet: 17 - 23 deg. F
Ridgetop winds forecast for the Sierra Crest: Southwesterly 15 - 25 mph, shifting to northerly
Snowfall expected in the next 24 hours: 1 - 2 inches

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2 Day Mountain Weather Forecast:
7000 to 8000 Feet
Today, mostly cloudy skies with snow showers in the afternoon. Snow accumulation around 1 inch. Daytime highs 24 to 29 degrees F. Southwest winds at 10 to 20 mph, shifting to north in the afternoon. Tonight, mostly cloudy with isolated snow showers in the evening. Lows 15 to 20 degrees F. North winds at 10 to 20 mph. Wednesday, partly cloudy skies. Daytime highs 28 to 33 degrees F. Northeast winds at 10 to 20 mph.

Above 8000 Feet
Today, mostly cloudy skies with snow showers in the afternoon. Snow accumulation around 1 inch. Daytime highs 17 to 23 degrees F. Southwest winds at 15 to 25 mph, shifting to north in the afternoon. Tonight, mostly cloudy with isolated snow showers in the evening. Lows 15 to 20 degrees F. North winds at 10 to 20 mph, gusting to 45 mph after midnight. Wednesday, partly cloudy skies. Daytime highs 23 to 27 degrees F. North winds at 15 to 25 mph, gusting to 45 mph. Wind gusts are expected to decrease to 35 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:
  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.