Avalanche conditions on Mount Jumbo remain dangerous, so people should still stay off the mountain.
That’s the assessment of avalanche experts with the West Central Montana Avalanche Center, who continue to monitor the snowpack on Mount Jumbo. Travis Craft, avalanche specialist and the center’s director, said the mountain will probably stay closed for a while.
“What we’ve found each time we’ve gone up there is dangerous avalanche conditions. Our primary concern right now is triggers,” Craft said. “The artificial triggers are what we’re worried about. That’s why we have the closures in place. It’s really important for people to respect those closures, because all three times we were there, we found ski tracks, as well as people and dog tracks.”
Artificial triggers are people or animals traversing the snow-covered slope, which can cause the snow to slide, such as the snowboarder who triggered the 2014 avalanche that crashed into houses below, killing one person and temporarily burying two others.
That tragedy prompted the city to be more proactive about closing the mountain when avalanche conditions start to worsen. The city now contracts with the avalanche center to develop a safety plan, when required.
A smaller slide happened last Friday, when elk triggered a small slide.
Craft is less worried about natural triggers, such as a heavy snowfall of 8 to 10 inches with strong, east winds or a rapid warming event, because none are predicted. The worst situation would be a rain-on-snow event.
That is one advantage Mount Jumbo has over the backcountry when to trying to predict the avalanche danger: Craft and his team know what kind of conditions are problematic. The same holds true with the three other urban areas that have to deal with in-town avalanches: Juneau, Alaska, and Ketchum and Sun Valley, Idaho.
“If we get the same weather pattern, we can probably correlate that to having urban problems, and we can take precautionary measures,” Craft said.
Fortunately, the forecast for the next seven to 10 days is a slight warm-up, with temperatures in the mid-30s during the day and freezing at night.
However, people should remain alert, especially those who live close to the base of Mount Jumbo. Even though parts of the mountain appeared scoured of snow, that doesn’t mean the danger is past.
“It’s going to take a warming event to get snow out of those loading zones and looking pretty barren,” Craft said.
Over the past couple weeks, Craft and his team repeatedly dug snow pits around the crown of the mountain and found the snowpack to be between 3 and 5 feet deep.
They also noticed that warming from what little sun we’ve had is making the snow somewhat unstable. So he recommends that people living along the base of the mountain avoid spending time in their backyards.
“We’re starting to have this warming event, and we’re starting to get these little roller-balls. That’s just surface instability, and it’s nothing to get alarmed about. But if people do have some debris that comes into their backyards, report that to the city. That gives us some information,” Craft said.
Because the mountain has such steep slopes, it doesn’t take too much to cause the crust to give and the heavy loose snow tumbles down. Slopes with angles of more than 30 degrees are prone to avalanches.
Assistant Fire Chief Brad Davis asked residents to report anyone they see on the mountain to the police.
Elk could present some risk, but Craft said their trails provide a bit of a benefit because they break up the snow crust so the pieces that do slide are smaller.
Surprisingly, Craft said, avalanche conditions in the backcountry around Missoula are not as dangerous as those on Mount Jumbo. The majority of the work done by the West Central Montana Avalanche Center is assessing backcountry snowpack.