Flathead Range & Glacier NP

Thin pockets of drifted snow exist near ridge crests and summits; these lapdog-sized slabs can have a big-dog bite on steep slopes above terrain traps. Be alert for these and maintain safe travel practices like riding one at a time and keeping a close eye on your partners. 

Sunday, a rider triggered a thin slab of drifted snow on an upper elevation, northerly slope near the crest of the Flathead Range. The rider self-arrested before being carried downslope. The slab was reported to be 2 to 3 inches thick. The party reported blowing snow at upper elevations, so it appears this slab had recently formed. 

That makes news the way Halloween pranks might make headlines in a small-town paper - there's not much else going on.  However, the incident is a good reminder of the isolated avalanche hazards that remain in this prolonged period of dry, stable weather. And of the importance of practicing safe travel habits, like exposing one rider at a time and watching them from a safe spot. Triggered slides are likely to be thin and not produce enough debris to bury a person. The terrain where you will likely find these slabs may be less forgiving. 

Other, similarly isolated hazards include triggered and natural sluffs of cohesionless snow. These could be dry or wet, depending on the aspect. I expect that the combination of sun and warming temps today will be enough to trigger rollerballs and point releases on steep slopes that receive direct sun. These won't likely entrain enough snow to be dangerous. 

Numerous glide cracks have appeared in all three mountain ranges. If you do choose to travel below these, don't dawdle. 

The incident may also offer a glimpse into the future. It didn't take much loading for a reactive slab to form, and it appears to have propagated widely. It likely released on weak, faceted snow. Similar conditions exist across the region, at all elevations. On slopes that get direct sun, melt-freeze crusts accompany the facets (image). Many observers also report large surface hoar crystals (image) on sheltered slopes. Expect conditions to change if snow arrives as forecast for next weekend. 

Interested in learning more? Check out our events calendar! There is a Ladies Intro to Avalanches course on Saturday, February 1st.