Northern Gallatin Range

Persistent slab avalanches breaking on weak layers buried 1-2 feet deep are possible, and the most likely places to trigger one are on previously wind-loaded slopes. Otherwise choose slopes sheltered from wind loading. High clouds and breezy conditions should prevent too much heating of sunny slopes, but watch out for ones where the snow gets wet more than an inch or two.

Ian put it best yesterday in our forecaster meeting “there are a lot of wild cards out there”. Buried weak layers of facets and occasional layers of surface hoar are lurking  in the snowpack from dry January and from shorter periods of dry weather in February.

• Yesterday a skier in the Hyalite area of the Northern Gallatin Range triggered a wet slab avalanche on a south facing slope about 12-18 inches deep.
• Alex spotted 6 recent avalanches near Cooke on Sunday.
• A skier triggered a slide on a small test slope in the Southern Madison Range on Monday.
• Ian and Andrea spotted a few slides and got more unstable test results on Lionhead near West Yellowstone on Monday.

Wet slab avalanches are notoriously difficult to predict except that they often happen when we expect wet loose avalanches. The party noted that it felt significantly warmer at that location than it had been throughout their day and the snow was wet through the slab down to the bed surface of the avalanche.

Even though the avalanche danger is MODERATE through most of the forecast area, it’s not open season. Various buried persistent weak layers up to 2 feet deep in most areas have created a lurking persistent slab avalanche problem. Wet snow is a possible problem today on sunny slopes, but several days cycling through warming then refreezing will limit this issue today. High clouds and winds may prevent much heating today.

Because the odds of triggering a persistent slab avalanche have decreased, getting onto steeper slopes isn’t out of the question, but take a few actions to stack the odds in your favor. Before heading out scroll through recent avalanche activity, and while on the snow: 

1. Riding slopes less than 30 degrees in steepness that aren’t steep enough to avalanche is always a great choice and my favorite.
2. Consider slopes with a clean runout free of trees, rocks, or gullies that make the consequences of an avalanche worse. Ask yourself, if this slope slides, where will it take me? Are my partners well trained in rescue and watching me from a safe location?
3. Do a quick extended column test on a small slope or low angle slope at the elevation & aspect you hope to ride. If you get an ECTP, don’t go.
4. Avoid sunny slopes where the snow is warming quickly and getting wet more than just an inch deep.

In the Bridger Range the danger is LOW today, and the main thing to watch for are wet loose avalanches on isolated slopes.