Selkirk Mountains

Strong winds and an inch or two of new snow may have formed fresh wind-drifted slabs on northwest through north to southeast-facing slopes at upper elevations. You could encounter drifted slabs around a foot deep near ridgelines and in gullies, and where triggering a slide would be easier and the ensuing slide larger. Steer clear of lens-shaped pillows of snow and back of slopes around 35 degrees if you see cracking in the surface. Even a small slide can become consequential in complex or extreme terrain where margins of error are slim.

If the North American Public Avalanche Danger scale was a linear progression between hazard ratings, today’s conditions might land somewhere between Level 1.8 and Level 2.1. However, the individual danger scale steps are more exponential between levels and crossing the threshold between LOW (1of5) and MODERATE (2of5) can be a much bigger deal than one individual tick on an ordinal number line - meaning more sensitivity and larger potential slide once that threshold is crossed. 

Today, there’s a lot of uncertainty around conditions focused on a couple of factors - 1) lack of field observations from Sunday limits knowing exactly how much snow transport occurred before snowfall, 2) marginal new snow reported by remote weather stations, and 3) where exactly did the strong winds deposit the snow on slopes or is it still floating around in the sky?

If in search of soft riding conditions, you will likely need to target northerly or leeward-facing slopes near and above the treeline. The caveat is fresh wind-drifted slabs likely reside there, and where you may trigger an avalanche larger than you want to manage for. The good news is you can identify this hazard by paying attention to what the snow surface looks like and whether you see evidence of recent drifting like fresh cornice growth or textured surfaces along ridgelines. Use small, non-consequential test slopes along the way to gauge sensitivity before charging into steeper terrain. Your day can turn bad real quick if you get knocked over or pushed around by a small slide in “no-fall” terrain or above a cliff.

Digging deeper, it’s now been two weeks since the last reported avalanche failing in the infamous January Drought Layer (JDL). The combination of warm, then cold, then warm, now cold again weather, and the lack of a major snow load have helped the snowpack stabilize and become well-bonded. However, the JDL persistent grains (facets and surface hoar) remain remarkably well-preserved under an almost meter thick slab. So if these grains still linger below and continue to produce sudden collapse failures in tests, then why did we remove the Persistent Slab avalanche problem? Well, the 3 to 5 inch rain event on February 23 has now refrozen into a thick, stout layer acting like an impermeable snowpack cap over deeper pesky grains.

At lower elevations, the rain reached the JDL and helped change the complexity there. Now those grains have mostly refrozen in place and will likely need another big warm-up to circle back into the realm of concern. At mid and upper elevations the JDL mostly avoided the wetting front, but the extremely stout slab above is helping deflect surface influence from a rider or machine. The isolated exception is on shallow, rocky slopes or in wind-scoured areas where these persistent grains are closer to the surface. Sticking to more planar slopes without cliffs, rock bands, or broad and steep convexities will help you avoid the random, shallow trigger spots and this low-likelihood scenario.

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