Flathead Range & Glacier NP

Riders continue to intentionally and unintentionally trigger soft slabs that break up to a foot thick. This kind of activity is most common at middle and upper elevations on leeward aspects where wind drifted snow into thicker, stiffer slabs. Manage this problem by sticking to terrain sheltered from the wind and keeping slope angles less than roughly 35 degrees. Stay out from beneath large, south-facing avalanche paths if you see the snow begin to glop up and rollerball.

Complex avalanche conditions should result in simple terrain choices. Although many of the recent avalanches have not been large enough to bury and injure you, don’t be caught off guard in terrain where recent snow is 8 or more inches thick. Slopes that face North through East just below ridgelines prove to be more reactive and dangerous than others. We currently have the distribution of the persistent slab problem on all aspects at middle and upper elevation to cover an uncertainty. Don’t be tempted by untouched powder on steep slopes or on slopes above terrain traps where a small avalanche can have large consequences. Buried surface hoar and near-surface facets are notoriously dangerous weak layers.

On Sunday, we made a transition to move from a storm slab to a persistent slab. This results from timing since the last snowfall and the pesky weak layer that recent snow is sitting on. Typical storm slabs will begin to heal, give or take 1 to 3 days after the loading event. We are stretching 5 days since the last noteworthy snow accumulation, and yesterday we received reports of numerous human triggered slab avalanches and one close call (observation 1, observation 2). A bump in winds and warm temperatures are contributing to settling recent snow into a cohesive slab. 

Watch warming temperatures and solar input as the day progresses. Temps are forecast to reach above freezing up to 6500 feet with the possibility of mostly clear skies. Yesterday’s relatively warm temperatures and sun roughed the surface, which will make wet loose less likely today. However, if you begin to see rollerballs or able to make a snowball easily, seek out shady slopes and watch for overhead hazards on south aspects.

There is an impressive number of glide cracks that are popping up all over the forecast area. There is a high degree of uncertainty forecasting glide avalanches. Warm temperatures can increase the likelihood. The best bet is to stay out from underneath these large cracks in the snow.

Thank you for the great observations and reports of close calls. Please, keep them coming. Observations are key to an accurate forecast and close calls are “free lessons” that everyone can benefit from.