Mid-Season Avalanche Report: Don’t Let Below-Average Snow Depths Fool You
At the halfway mark, the 2013-2014 winter season has been nothing if not out-of-the-ordinary – some would say even quirky.
However, avalanche forecasters insist that the depth of snow on the ground – or lack of it -- doesn’t have much effect on the frequency of avalanches in the Mountain West. A growing number of skiers and snowboarders continue to venture beyond the ropes, consistently raising the chances of human-caused snow slides.
In much of the West region, forecasters note that the early-season snowfall has had ample time to change from cohesive powder to a less stable sugar-like snow – a process called faceting. When a storm drops more on top and there’s little cohesion within the layer below, the weight of the new snow causes the lower layer to fracture and slide downhill, they say.
Potential avalanches only await the next storm, even in the Sierra Nevada, which hasn’t had snow since early December and currently has about 20 percent of normal snowpack.
“Now, we have a persistent deep slab problem, with a shallow layer that’s like sugar,” Brandon Schwartz, forecaster for the Tahoe National Forest’s Sierra Avalanche Center, told SnoCountry.com. “It’s stable right now because nothing’s on top. But add a significant storm, say a foot at a time, and it’s like putting a brick on top of a house of cards.”
The Northwest has had one of the driest early seasons in memory. Several resorts only recently opened as snow finally began to fall in mid-January, but it didn’t take long for an avalanche to fatally bury a climber near Barlow Pass.
“Less snow doesn’t mean fewer avalanches,” Garth Ferber, avalanche meteorologist at the U.S. Forest Service’s Northwest Avalanche Center, explained to SnoCountry.com. “Even though we have a lot less right now, significant snowfall on top won’t be supported underneath.”
Statistics from Avalanche.org confirm Ferber: So far this season, the 10 avalanches involving skiers, snowboarders, climbers or snowmobilers is about the same as the previous two seasons.
In Colorado, the highly publicized avalanche death of the grandson of the co-founder of Vail re-emphasized that even a slope of modest-depth snow will fracture and slide.
“We now have a situation where the snowpack is structured with a buried weak layer, often a winter hoar that last a long time,” Brian Lazar, of the Colorado Avalanche Information Center, told us. “So any new layer on top will be sitting on a very weak layer below. If the snow gets wind-blown, then you have crust that is also weak and can’t support new snow on top.”
In the Utah mountains, forecaster Drew Hardesty of the Utah Avalanche Center, characterized the winter so far as “generally spooky.”
“We’re drier than average, about 70 percent,” Hardesty said. “Less snow actually means more danger down the road, as the high pressure periods between storms foster weaker layers that are easily overloaded when new snow comes on top.”
Utah averages about four deaths a season due to avalanches, Hardesty said, but luckily, no one has died because of an avalanche in Utah so far this season. Five have been rescued from burial in the last two seasons.
Hardesty attributed that, in part, to heightened education programs by the center and Utah resorts that have greatly improved backcountry adventurers’ expertise with avalanche prevention equipment.
Unavoidably, the oddity of this season’s weather patterns begs the question: Is climate change to blame?
The avalanche forecasters with whom we spoke were all reticent to make that connection, citing lack of long-range data.
“I want to you to know that there hasn’t been any peer review on this, but my ‘garage observation’ is that there’s more rain at all elevations in the winter,” said Hardesty. “Also, the last three winters have been well drier than average, but there haven’t been any ‘ah-ha’ moments about climate change yet.”
Who knows what the rest of season will hold.
Colorado’s Lazar expects a mid-winter drought followed by a wet spring, much like last season. Ferber of the Northwest center said the crystallizing effect of any rainfall that subsequently freezes will heighten avalanche potential, while the Sierra’s Schwartz keeps looking out the window and seeing “a snowpack that’s from another part of the country.”
But they all agree on one thing: While a couple of long, large powder dumps will greatly improve the conditions on the slopes, the potential for dangerous avalanches will remain until everything melts in the spring.
Photo: Skier at avalanche fracture in Utah (Utah Avalanche Center/Facebook)