Avalanche risk 'considerable' for Tahoe Basin, Sierra Avalanche Center issues advisory

SOUTH LAKE TAHOE — In anticipation of this week’s winter storm, the Sierra Avalanche Center raised its backcountry avalanche threat from low to considerable Thursday — level three on their five-tier scale.

“Avalanche danger will remain elevated through the weekend,” avalanche forecaster Andy Anderson told the Tahoe Daily Tribune. “We’re going to get a lot of wind. That, combined with our new snow amounts, will provide some pretty unstable wind slabs.”

The advisory is calling for caution in any avalanche prone terrain below, near and above tree line, especially on northwest and north through southeast facing slopes.

In addition, wind-loading northwest through northeast facing slopes will be susceptible to deeper persistent slab dangers — weak layers deeper in the snowpack that could cause a larger slide to release.

“They aren’t the kind of problems that go away quickly,” Anderson said of deeper weak layers. “We were getting unstable results (in existing snowpack) before the new snowfall.”

Based on the advisory, natural slides will be possible with human-triggered avalanches likely.

“Those human-triggered avalanches are the most worrisome,” Anderson said, reminding backcountry users slopes with above a 30-degree angle are most susceptible.

Travel immediately beneath those slopes can also cause a slide to release from above.

“The typical 24-hour rule is completely false,” he added of the tendency for some backcountry users to assume conditions stabilize shortly after a storm. “Most incidents occur more than 24 hours after a storm.”

And with another storm in the forecast as early as Sunday, the threat may remain.

“The storm door is open right now,” said Bryan Allegretto, regional snow forecaster for OpenSnow.com, describing weather patterns conducive to more weather systems passing through the Tahoe Basin.

With more snowfall on the way, Anderson said the cause for concern will likely remain.

“I’m not telling people not to go out,” he said. “I’m telling people to be careful. You can find safe places to travel.”

Coming off of four down snow years, backcountry travelers should remember to be especially cautious when it comes to fighting the urge to push limits.

“We’ve been in four years of drought. People are really excited to get out,” Anderson said.

“That excitement makes it really hard to make the right decisions.”

He suggested planning a route in advance and sticking to it, because in the moment, looking at a fresh line, warning signs can be easy to ignore.

“It’s really hard to make a rational decision at that point,” he said.

Avalanche incident reports frequently site ignoring warning signs as a cause for a slide. That was the case with the Tahoe Basin’s first skier triggered avalanche earlier this season.

More information and a daily forecast is available at www.sierraavalanchecenter.org.