New snow last week has refilled mountain stocks and sent skiers flying to area resorts, but is also leading to a more reactive and dangerous snowpack, according to regional avalanche forecasters.
The Idaho Panhandle Avalanche Center advised against backcountry travel in the St. Regis and Silver Valley regions Friday. The nonprofit also urged caution and conservative decision-making in the Selkirks and Cabinet mountain regions.
“Winter is back with a vengeance after we have had a snow drought for so long,” the advisory said, noting that the nearly 12 inches of snow that fell in the Silver Valley buried a widespread surface hoar layer.
Surface hoar is essentially frost – like what you scrape off your car window on cold mornings. The crystals form during clear and calm conditions, according to avalanche.org.
Once buried by snow, the crystals don’t adhere well to the snow above or below, creating a weak layer that can last for days, weeks or the entire winter. That layer can be difficult to detect.
On Tuesday, Jeff Thompson, the director of the Idaho Panhandle Avalanche Center, snowmobiled up Trestle Creek to take snow measurements for the avalanche forecast. Even driving up he saw signs of unstable snow and urged caution, he said.
The heavy and wet snow that fell last week and is predicted to continue this weekend may be a blessing in disguise.
“Putting some heavy snow on top of this surface hoar is kind of good,” Thompson said.
“It will flush it out in places where we want it to be gone. … Hopefully, it will go naturally.”
He urged backcountry travelers to consider how and where the wind is piling up snow.
“Stay away from underneath wind-loaded slopes,” he said. “Because I think that’s our best chance of producing big avalanches right now.”
The Cascade Range’s snowpack is “generally at or above average for most locations,” said Dallas Glass, the deputy director of the Northwest Avalanche Center.
The relatively warm winter has “resulted in thinner snowpacks at lower elevation and deeper snowpacks at higher elevation,” he said. It has been a wetter year than average. The formation of a persistent weak slab lower in the snowpack, similar to the layer seen in the North Idaho, has worried forecasters.
While it’s good to be aware of longer-term snow and climate trends, Glass emphasized the importance of checking the local avalanche forecast regularly.
“The avalanche forecast is just like a weather forecast,” he said. “It changes daily.”
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