Backcountry danger has increased following a series of storms that slammed into the Sierra this week.
Sierra Avalanche Center advisory Friday warned of widespread instability in the snowpack, listing avalanche danger as high on steeper slopes above tree line. Considerable avalanche risk is noted on below tree line slopes.
Travel in avalanche terrain is not recommended during times of high avalanche danger, according to the North American Public Avalanche Danger Scale. Careful snowpack evaluation, cautious route-finding and conservative decision-making are essential during times of considerable avalanche risk, according to the scale.
People were observed Friday by an avalanche forecaster heading into the backcountry, but the 70 inches of new snow along some parts of the Sierra Crest limited the distance they traveled.
"There are people out there, but they're not getting very far from their vehicles because the snow is so deep," Brandon Schwartz said.
The threat of natural avalanches is expected to decrease as storms taper through the weekend, but the risk of human-triggered slides is likely to persist, Schwartz said.
Deposits of wind blown snow are the primary avalanche concern.
"Once avalanches initiate, there is a significant possibility that the slabs may step down to deeper layers within the storm snow or simply entrain much of the deeper storm snow," Friday's advisory warned. "This could serve to greatly increase the size and destructive potential of any natural or human triggered avalanches that occur today.
"Very unstable instabilities," within the snow from this week's storms also present a risk of avalanches, especially in response to a backcountry user, according to the advisory.
Nine people in the United States have been killed in avalanches this season, including a ski patroller who was conducting avalanche control activities inbounds Nov. 22 in the Wolf Creek Pass Ski Area, according to the Colorado Avalanche Information Center.
None of the deaths were in California, which did not record an avalanche-related death in 2009-2010. Three people were killed in avalanches in the state during the 2008-2009 season, according to the statistics.
Schwartz recommended people take an avalanche course and check the latest avalanche conditions at www.sierraavalanche
center.org before heading into the backcountry.
"You control your own risk by controlling when, where and how you travel," Schwartz said.
The daily advisories cover the area between Yuba Pass to the north and Ebbetts Pass to the south and are developed through on-the-ground observations.
Apart from a handful of days during the last several weeks when the Sierra Avalanche Center's daily advisory noted "moderate" avalanche risk on some aspects, the risk of slides has been rated "low."
