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 3, 2010:


February 3, 2010 at 7:51 am

Near and above treeline, pockets of MODERATE avalanche danger exists in wind loaded areas. Below treeline, avalanche danger is LOW in wind protected areas.


Forecast Discussion:


A weak weather system affecting the forecast area this morning is expected to taper off by mid day. A few scattered snow showers will continue this afternoon, mainly in the far northern portion of the forecast area. New snow amounts of 1 to 3 inches have accumulated overnight. Up to an additional inch of accumulation is expected this morning. Southwest ridgetop winds are moderate to strong in speed this morning. Winds are forecast to remain out of the southwest today and decrease to moderate in speed. Expect air temperatures in the mid 20s to low 30s today. A short lived period of high pressure will move through the area overnight before the next storm system impacts the area late Thursday.

Observations:

Observations made yesterday on Hidden Peak (West Shore Tahoe area) found no evidence of snowpack instability in below treeline and near treeline areas on N-NE-E aspects between 6,500' and 9,130' (pit profile, video). Melt freeze conditions were noted on northerly aspects up to 7,300'. Observations made on Becker Peak and Talking Mountain (Echo Summit area) also found no evidence of snowpack instability. Test pits and ski cuts on steep N-NE aspects in recently wind loaded areas near treeline at 8,680' showed no evidence of unstable slabs existing yesterday (more info). Several day old debris from previous human triggered test slope failures were noted on adjacent wind loaded slopes, indicating that unstable slabs had existed in this area previously.

Avalanche Concerns:

Avalanche concerns for today focus on new wind slabs that formed overnight with the combination of new snow and SW winds. Instability will mainly occur near and above treeline on wind loaded NW-N-NE-E aspects. Isolated areas of instability may exist in below treeline areas that receive wind loading, effectively allowing them to act as near treeline terrain. Wind slab instability that occurs today is expected to remain limited to the top one foot or less of the snowpack. Natural avalanche activity is unlikely, human triggered avalanches are possible.


The bottom line:

Near and above treeline, pockets of MODERATE avalanche danger exists in wind loaded areas. Below treeline, avalanche danger is LOW in wind protected areas.


Brandon Schwartz - Avalanche Forecaster, Tahoe National Forest


Weather Observations from along the Sierra Crest between 8200 ft and 8800 ft:

0600 temperature: 23 to 26 deg. F.
Max. temperature in the last 24 hours: 33 to 35 deg. F.
Average wind direction during the last 24 hours: Southwest
Average wind speed during the last 24 hours: 27 mph
Maximum wind gust in the last 24 hours: 60 mph
New snowfall in the last 24 hours: 1 to 3 inches
Total snow depth: 71 to 109 inches

Two-Day Mountain Weather Forecast - Produced in partnership with the Reno NWS

For 7000-8000 ft:

  Wednesday: Wednesday Night: Thursday:
Weather: Mostly cloudy skies with scattered snow showers. Mostly cloudy skies. Cloudy skies with a slight chance of snow showers in the afternoon.
Temperatures: 26 to 34 deg. F. 21 to 26 deg. F. 28 to 36 deg. F.
Wind direction: SW SW SW
Wind speed: 10 to 15 mph with gusts to 25 mph. 10 to 15 mph with gusts to 25 mph in the evening. 10 to 15 mph with gusts to 35 mph in the afternoon.
Expected snowfall: Up to 1 in. O in. 0 to 1 in.

For 8000-9000 ft:

  Wednesday: Wednesday Night: Thursday:
Weather: Mostly cloudy skies with scattered snow showers. Mostly cloudy skies. Cloudy skies with a slight chance of snow showers in the afternoon.
Temperatures: 23 to 28 deg. F. 19 to 24 deg. F. 26 to 33 deg. F.
Wind direction: SW SW SW
Wind speed: 10 to 20 mph with gusts to 30 mph. 10 to 20 mph with gusts to 30 mph. 10 to 15 mph increasing to 15 to 25 mph with gusts to 40 mph in the afternoon.
Expected snowfall: Up to 1 in. O in. 0 to 1 in.