El Niño drives in more snow storms — and possibly avalanches

With a strong El Niño expected to bring above-average storm activity to the region, local forest rangers are on alert for the hazards extra snow can bring. Though rare, deadly avalanches have killed several people in the region. Notably, in 2008, three people died in a series of slides that happened within a week.

On a recent Tuesday, Nathan Judy, a fire information officer for the U.S. Forest Service at the Angeles National Forest, drove into the Mt. Baldy area to check on the conditions three days after a series of storms dumped snow on the mountaintops. 

Judy had previously been a snow ranger for the Angeles National Forest for eight years, and his old skills are needed, because recent turnover has left only a few individuals on staff with proper snow training. He said with the expectation of high snowfall this winter, it's especially important to monitor for potential avalanches.

“We know it’s coming. We just have to make sure we’re vigilant out here in the forest where the public’s at, so we can monitor the area in case there is something that happens. We can help people out, if they need assistance, or we can close areas off when they need to be closed,” Judy said.

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The Mt. Baldy area of the San Gabriel Mountains covered in snow.

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Courtesy of Andrew Mitchell/Forest Service

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Beyond regular monitoring, proper preparation requires understanding the nature of the snow as it falls and after it lands and is affected by temperature changes. Snow rangers check stability by digging pits, the walls of which exhibit layers of snow. By examining the composition and solidity of the differing layers, rangers can estimate the likelihood of a slide. 

U.S. Forest Service fire information officer Nathan Judy digs a snow pit at Manker Flats, near Mt. Baldy. The pit walls will give a picture of the layers of snow that fell.

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Jed Kim/KPCC

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During periods of concern, rangers will check one to three sites daily, taking a suite of measurements at each. The locations vary according to the direction they face and the degrees of shade and sun that hits them. The measurements include depth, temperature and structure of the snow. 

Nathan Judy examines the snow at Manker Flats in the Angeles National Forest. Snow rangers identify areas that may be at risk of avalanche.

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Jed Kim/KPCC

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The structure of the snow can vary greatly. Judy used a reference grid to judge the size of the individual flakes or ice balls contained within each layer of the snowbank. 

During the recent storms, rangers had been concerned that thick snow could be accumulating on top of ice, making it possible that damaging sheets of snow could slide off in large chunks. Days of subsequent sunshine, however, seemed to have melted the layers together into a safer, more stable mass.

"Looking at this, all the way at the bottom, maybe an inch and a half, it’s very stable. Then, you have a layer of ice in there, which has some balls, but see, if those balls were not cohesive, and they were floating around inside there, you’d have a layer of instability," he said.

Snow rangers analyze the types of snow, judging size and structure. That helps them understand the stability of the snowbank.

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Jed Kim/KPCC

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Judy grew up in La Verne with the San Gabriel Mountains nearby, which allowed him to get an early feel for being in snow. 

"This was my backyard as a kid, so I’d come up here to go hiking, to go recreating — snowboarding in wintertime. We even ditched school in high school — to come up here in the snow and fill the back of the truck up and bring it back down to school and play, have snowball fights in high school. But for myself, I wanted to give back to nature, and that’s why I went to school for Forest Service and started volunteering. That’s how I got my job up here,” he said.

Despite his familiarity with snow, Judy said his appreciation and understanding of it deeply changed as a result of his studies and work as a snow ranger.

“Oh, night and day," he said. "Playing in the snow is a lot different from having an intimate knowledge of the snow and knowing the snow science behind why the snow falls the way it does and how it packs together."

Nathan Judy records the temperatures within each layer of snow.

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Jed Kim/KPCC

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Temperature gauges often reveal different temperatures within a snowbank. The temperatures reflect the composition of the water within the bank.

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Jed Kim/KPCC

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From his measurements, Judy was able to determine the Manker Flats sledding area was unlikely to be in any danger of an avalanche. With months of winter left, he'll likely be back to the area again. He said, though, that he doesn't mind because of his fascination with the science of snow — something he hasn't had much chance to indulge during the recent years of severe drought. 

"Very interesting! I enjoy doing it when I get the chance to come out, but I haven’t had that for a few years, so it’s nice to have the snowpack back," he said.