Flathead Range & Glacier NP

A skier was caught and carried in an avalanche Monday. This incident highlights our reactive Persistent Slab problem. Weak layers buried 1-4 feet below the surface are responsible for multiple triggered avalanches over the past three weeks. Thin slabs may develop with today's increasing winds. Cracking in the snow surface is clear evidence that you have found instability. Choosing low-angle terrain not connected to steeper slopes above is the key to navigating our difficult Persistent Slab problem. 

On Monday a skier-triggered avalanche in the southern Whitefish Range adds to a long list of accidentally, remotely, and intentionally triggered slides over the past three weeks. Most of these have occurred in buried weak layers resting above the 1/13 crust. These layers formed mid to late-January and have remained reactive in parts of our area for nearly three weeks. The individual involved with this avalanche provided an excellent summary, which we can all learn from. We thank them for sharing their story, which benefits the backcountry community. Read the complete observation here. 

“As I was traversing on a roughly 30-degree slope, (estimated), I heard a boom from above me. The avalanche fractured directly above me about 10 feet or so. I was caught and carried roughly 30 feet before it stopped. I was buried to my neck, but I was very close to the surface, so I got myself out easily. I never would have thought I could have triggered something at that angle, which I estimate was maybe 30 degrees.”

Monday, Cam was in Canyon Creek, where he found reactive buried surface hoar in snowpits on the west and south-east aspects. His pit on a west aspect resulted in an ECTP 7 with the block popping out into his lap. On a southeast slope, he had an ECTP 23. In the upper Whitefish River, a ski cut produced an R2D2  avalanche at the old snow/new snow interface, although we are unsure of the failure layer in this slide. Sunday, an observer noted collapsing (whumphing) while skinning on north slopes at 5700 feet in Canyon Creek. At the same time, Cam initiated a Persistent Slab avalanche in the Swan Range with an intentionally kicked cornice. These observations confirm that weak layers exist around our forecast area and should not be trusted. As Cam noted, “It will pay to do your homework before committing to anything on south aspects. I'm writing off north and east aspects for some time still.”