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 6, 2010:


March 6, 2010 at 7:52 am

Avalanche danger is LOW for all elevations and aspects. Very isolated areas of instability may exist. Snowfall amounts greater than forecast expectations could create isolated areas of locally higher avalanche danger today.


Forecast Discussion:


A weather system is passing to the west and south of the forecast area today. Significant cloud cover and scattered snow showers are expected across the area. Isolated locations may see 1 to 2 inches of new snow accumulation under spotty heavier snow showers. Ridgetop winds shifted from south to northeast early yesterday afternoon and continued overnight. Ridgetop winds increased to moderate in speed overnight and were strong enough to move snow. Northeast to east ridgetop winds are expected to remain moderate in speed into tomorrow morning.

Observations:

Very isolated and small wet point release skier triggered avalanche activity occurred yesterday afternoon on Mt. Judah (Donner Summit area) in a large open area below treeline at 7,200' on an E aspect 40 degree slope near exposed rocks (photos, more info). This is the only significant evidence of instability observed yesterday. Observations made yesterday on Mt. Lola (Independence Lake area) showed no evidence of instability. Snowmobile cuts made below treeline between 6,000' and 8,800' on NE-E aspects on slope angles of 30 to 40 degrees produced no signs of instability. Snowpit data collected near treeline at 9,070' on a NNE aspect 32 degree slope revealed no additional evidence of instability. Observations made yesterday on Relay Peak (Mount Rose area) also showed no evidence of instability. Intentional skier triggered cornice collapse in several previously wind loaded areas above treeline around 10,000' on N-NE-E aspects produced no evidence of instability. Snowpit data collected near treeline at 10,135' on an E aspect 36 degree slope revealed only very minor evidence of instability existing around 6 inches deep in the snowpack at the base of the most recent storm snow (photos, pit profile, more info). Significant skier and snowmobiler traffic on steep terrain in the area was noted with no avalanche activity occurring.

Avalanche Concerns:

Avalanche concerns for today focus on areas where wind loading occurred last night and may continue today. NE to E winds last night were strong enough to move snow and may have caused some shallow slabs to form on SE-S-SW-W-NW aspects in wind loaded areas. Snow showers may add a quick 1 to 2 inches of new snow today in isolated areas under continued wind loading from NE to E winds. Some isolated areas of unstable shallow surface slabs may exist in near and above treeline areas today. For the most part, these slabs area expected to be small and not present a significant hazard to backcountry travelers. Larger unstable slabs could form today in very isolated areas if snowfall amounts exceed forecast expectations of 1 to 2 inches.


The bottom line:

Avalanche danger is LOW for all elevations and aspects. Very isolated areas of instability may exist. Snowfall amounts greater than forecast expectations could create isolated areas of locally higher avalanche danger today.


Brandon Schwartz - Avalanche Forecaster, Tahoe National Forest


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

0600 temperature: 22 to 27 deg. F.
Max. temperature in the last 24 hours: 32 to 39 deg. F.
Average wind direction during the last 24 hours: South shifting to east
Average wind speed during the last 24 hours: 20 mph
Maximum wind gust in the last 24 hours: 43 mph
New snowfall in the last 24 hours: O inches
Total snow depth: 89 to 123 inches

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

For 7000-8000 ft:

  Saturday: Saturday Night: Sunday:
Weather: Cloudy skies with isolated snow showers in the morning. Scattered snow showers in the afternoon. Cloudy skies with scattered snow showers in the evening. Isolated snow showers after midnight. Mostly cloudy skies with scattered snow showers.
Temperatures: 29 to 36 deg. F. 21 to 27 deg. F. 29 to 36 deg. F.
Wind direction: E NE NE
Wind speed: 10 to 15 mph with gusts to 25 mph. Around 10 mph. Light winds.
Expected snowfall: trace to 2 in. trace in. trace in.

For 8000-9000 ft:

  Saturday: Saturday Night: Sunday:
Weather: Cloudy skies with isolated snow showers in the morning. Scattered snow showers in the afternoon. Cloudy skies with scattered snow showers in the evening. Isolated snow showers after midnight. Mostly cloudy skies with scattered snow showers.
Temperatures: 23 to 29 deg. F. 19 to 24 deg. F. 25 to 30 deg. F.
Wind direction: E NE NE
Wind speed: 15 to 25 mph with gusts to 40 mph. 10 to 15 mph with gusts to 30 mph in the evening. Up to 10 mph in the morning becoming light.
Expected snowfall: trace to 2 in. trace in. trace in.