Avalanche monitors issued warnings Thursday morning of increased danger in the mountains as a winter storm bore down on northwest Montana.
With a forecast of rain below 6,000-feet elevation across much of western Montana on Thursday followed by heavy snow Friday, conditions look bad for backcountry travel in steep terrain. Strong winds also are expected to rake the area, likely increasing avalanche danger as the storm progresses.
The West Central Montana Avalanche Center posted a “Considerable” danger level for wind-loaded terrain across its backcountry region Thursday. Analyst Logan King said between 1 to 4 inches of new snow has accumulated, but temperatures didn’t drop below freezing Wednesday night and rain was falling as high as 5,500 feet Thursday morning. Winds in the region were blowing out of the southwest and west-southwest, between 15 and 25 mph.
“I toured near Lolo Pass yesterday and found strong winds that were cross-loading slopes,” King wrote in his Thursday advisory. “The wind-loaded areas were touchy and shooting cracks were easy to initiate while traveling on or near wind deposits.”
King said other analysts in the southern Swan Range also found wind slabs and signs of loose, wet snow activity.
“With extended rain on snow, wet slab avalanches can become problematic as the day progresses,” King wrote. “Avoid steep terrain where the snowpack is showing signs of saturation as wet slabs are notoriously hard to predict.”
Flathead Avalanche Center staff posted a “High” advisory for avalanche conditions in the Flathead Range and Glacier National Park through Friday morning, noting a combination of rain, snowfall and strong winds had stressed multiple weak layers in the snowpack. It noted that large and destructive avalanches are likely to fail naturally in that period, and may run long distances into mature forests, valley floors and flat terrain.
Driving conditions should also worsen as the storm intensifies Thursday evening. National Weather Service meteorologists warned the Kalispell area of high impact for heavy mountain snow, moderate snow in the valleys, reduced visibility and single-digit windchill readings.
The Missoula area was expected to get rain Thursday morning replaced by snow and wind gusts up to 39 mph Thursday evening. Friday has a 60 percent chance of snow and wind gusts of up to 21 mph. Low temperatures on Friday could dip into the low teens.
Meanwhile, the balmy Bitterroot had highs in the 50s Thursday, with a 50 percent chance of snow on Friday. The weekend forecast calls for clear skies and temperatures in the mid 30s.
The weak layers in the snowpack in northwest Montana can be traced back to rain over the Thanksgiving weekend that was followed by cooler temperatures and little snow before a prolonged dry period in the first half of December, said Chris Bilbrey, an avalanche specialist with the Flathead Avalanche Center. Since then, the mountains have received frequent bouts of moisture in the form of snow and rain.
“The storms have been really complicated that have impacted our region,” Bilbrey said. “They come in with a lot of moisture battling cold arctic air coming over the divide. We have multiple buried rain crusts that vary through elevation and aren’t totally consistent within our mountain ranges.”
Some areas received more rain or have been affected more by the cold that created weak faceted grains around the rain crusts.
“That’s what’s created these persistent weak layers,” Bilbrey said. “We call them persistent because they can linger for days, weeks or even months …Those weak layers can become reactive during large loading events.
“Unfortunately, we have an extremely complex, poor snowpack structure,” he said. “It’s just not going to heal or gain strength in a short window of time. We sort of feel like it’s groundhog day around here, but the words persistent slabs are there for a reason.”
The former director of the avalanche center said this is “scariest snowpack that he’s seen since 2014,” Bilbrey said. “There are a lot of savvy backcountry recreationalists and professionals in this area that have a lot of respect for the snowpack structure and potential for producing large avalanches.
“It’s one of those years when patience and conservative decision making is important for anyone traveling in the backcountry,” he said.
While the complex snowpack creates challenges for backcountry skiers, those who chose to carve turns at local ski areas couldn’t be happier.
Whitefish Mountain Resort’s public relations manager Riley Polumbus said total snowfall at the ski resort could reach record levels before the season is over.
So far, 251 inches of snow has fallen at resort’s summit with more expected to arrive later Thursday.
The record snowfall of 426 inches came in the 2007-08 season.
In that record year on Feb. 8th, the mountain recorded a total 118 inches of settled base. This year that number stands at 126 inches.
“No matter how you look at it, everyone’s happy right now,” Polumbus said. “Right now, it’s a little bit wetter and warmer than we would like to see it, but the temperatures are supposed to drop and Saturday the forecast calls for sun. That’s like a grand slam homerun.”
Overall, skier numbers and reservations are trending in the right direction.
“We still have half a season to go,” Polumbus said. “If the trajectory remains the same, we’re going to be in good shape.”
Lost Trail Powder Mountain is reporting 238 inches of snowfall with a 65-inch settled base.