Swan Range

With lingering avalanche hazards at low and upper elevations, careful terrain choices and safe riding practices remain important. You can minimize your chances of surprises by riding planar or concave slopes less than 35 degrees that are sheltered from the wind.  Similarly, you can minimize the consequences of surprises by riding one at a time with a full set of avalanche rescue gear. 

What do you do with a problem like the surface hoar in the southern Whitefish Range? In the past 8 days, riders have triggered a series of slides on slopes that broke on well-developed surface hoar about a foot below the surface on north-, northeast-, and east-facing slopes in this corner of the region. One left a rider pinned to a tree and lucky to be uninjured. The most recent occurred Monday. Yet tests on nearby slopes are not producing propagation, even when the grey stripe is obvious.  And most parties in the area aren't reporting collapses or cracking. The most straightforward answer? Avoid terrain with similar characteristics, or at least approach it carefully, testing with hand pits and slope cuts before commiting. And most importantly, riding with avalanche rescue gear and keeping your partners in sight, so any surprises have minimal consequences. One note - the reported slides were triggered on slopes near or just below ridge crests, where wind-blown snow has likely stiffened the slabs. Mid-slope convex rollovers are another likely trigger point.

Outside of the southern Whitefish Range, the primary concerns are layers of facets near melt-freeze crusts. These layers are also buried six to 18 inches deep. They're widespread, and people have reported collapses and some propagating failures in large column tests in the Flathead Range. We've had one report of a possible triggered slide outside the southern Whitefish Range. This occurred in the northern Whitefish Range and may have been machine-triggered. That's not enough evidence to write this structure off. Not for me, anyway. I'm still looking for ascent routes free of overhead hazard and on slopes less than 30 degrees, and descending planar or concave slopes that aren't above terrain traps like gullies. Small efforts that may keep any surprises small and manageable. 

The winds... Upper elevations saw winds strong enough to peel paint off a wall early this week. Plumes of blowing snow were obvious at ridges, and the winds even worked into usually sheltered terrain, hardening snow surfaces. It also left a lingering hazard of hard slabs on steep, top-loaded and crossloaded slopes. It's hard to distinguish these from harmless wind crusts without digging. Avoiding steep terrain likely to harbor these slabs is more straightforward. Many freshly-formed cornices may sag and break in the warm weather; the falling debris can trigger hard slabs on slopes below, so scurry through ruouts below ridges with cantilevered cornices.