It’s that time of year when our beloved Sierra Avalanche Center (SAC) stops issuing daily avalanche advisories. Due to a tight budget SAC is only able to operate from the late fall to the early spring each season. Granted this is when the majority of backcountry users are fired up on the season, but when these advisories stop more often than not the real spring skiing season is just getting underway. Recently, I was fortunate to link up with an observer for SAC to get out for a day of local backcountry skiing. Over the course of our day I was able to follow along with how observations made from our session would help influence the next avalanche advisory, as well as gain a better understanding of how the SAC functions as a unit, and how overwhelmingly important their work is to backcountry users in the Tahoe Basin.
SAC primarily operates under the guise of a board of directors with two main forecasters that are USFS employees. They also have two observers who are actually independent contractors. SAC is a nonprofit, and although some of their funding comes directly via the USFS, most of it comes from public donations and through fundraising efforts in our community. SAC would cease to exist as we know it today without your support!
On a typical day during forecasting season four people help craft avalanche advisories. They do so in a very solid, systematic manner where one member of the team might be on the North or West Shore, and another might be on the South Shore. When things are really “interesting” in the backcountry they might even have three people out in the field. Whether it’s forecasters or observers, team members head out into the field already having a baseline history for what’s been going on in our local backcountry in terms of avalanche activity. Based on previous locations visited in the near-term another location is identified for the next day to make updated observations. Of course these boys like to ski too so getting to climb up and slide down something fun is always a bonus.
Depending on the current conditions the forecaster or observer will identify where to dig a pit to engage in a more detailed analysis. During our session Travis and I skinned for a while, skied our objective, and peeled off to an area to dig that he had already identified on the way up. During this day, based on previous observations made in the past several days, Travis knew he was looking for the potential for water percolating down into a persistent weak layer (PWL), the same one that has threatened stability in the Tahoe area for several weeks. He knew wet snow instabilities were going to happen due to daytime warming as is, but based on a simple pit was able to analyze the differences between wet snow consistency throughout the pit, find where snow turned dry and cohesive, and locate where a crust had formed after the most recent snowfall. Depending on conditions, multiple pits or even a full profile pit might be dug. However, if one pit contributes to the overall picture like this one happened to do on this given day then that’s enough to help shape the advisory for the next day.
Once Travis made observations I was told this information would be sent back to Andy and Brandon who are the two main employees that crunch all this field data into a computer program and make sure we’re able to access an updated avalanche advisory early the next morning. Field information combined with actual weather data from remote stations, checked early in the morning before the avalanche forecast is published, along with the coming day’s weather forecast and previous snowpack history is what all gets combined to produce the reports you and I read each morning. It’s an amazing amount of work, an amazing effort, and clearly the SAC team is an all around amazing group of savvy backcountry professionals. We’re beyond lucky to have them doing what they do so I hope you’ll either take the time to thank them in some way during the off-season or prepare to offer some support their way when they’re getting ready to fundraise next fall.
You can read their last advisory of the season linked here.
Thanks for everything SAC, you’re a major part of what makes our backcountry community as special as it is!!!