Selkirk Mountains

Human triggered avalanches are possible today from recently formed slabs of snow that sit on top of widespread weak snow layers and a firm crust. These slabs are thicker and stiffer on previously wind loaded slopes where they are likely to be more reactive to human disturbance and could produce a large avalanche. With how fragile the weak snow layers are below the recent snowfall, provide yourself with an extra buffer traveling adjacent to or directly below slopes around 35 degrees to account for the increased chances of remote trigging an avalanche from a distance.

Today’s danger rating is what industry insiders often refer to as “Spicy-Moderate.” The conditions are such that we as forecasters get down in weeds weighing distribution, sensitivity and trends to determine what side of the Considerable/Moderate divide to assign the danger rating. However, the long and short of it is that the nature of the avalanche problem has not changed significantly, a slab sitting over persistent weak layers is our main concern. What determined the drop from Considerable to Moderate today is the cessation of active loading from precipitation as we enter this dry spell means that natural slab avalanches are unlikely, but human triggered avalanches remain possible. Snowfall from the last week fell on very worrisome weak layers, most notably a layer of large, buried surface hoar that has been found on all aspects above about 5500 feet. This weak layer was initially buried by light snowfall on January 28th, and in many locations, strong southwest winds and settling have helped strengthen the overlying slab over the past few days, however variability of the volume of snow and slab thickness, favoring our Nothern zones, means the distribution of the problem is not uniform.

In the Silver Valley and Bitterroot Mountains, the danger remains Low in part due to higher freezing levels, but mostly due to significantly less snowfall within the past week (Bitterroot Mountains Observation). Up north, the buried surface hoar appears to be almost everywhere above the recent rain/snow lines persistent weak layers and it is now buried up to a foot below the surface in favored locations. Recent observations have uncovered very large feathers, intact and upright, having survived even in areas atypical like open slopes on the windward side of ridgelines, or directly on the ridgetops (Selkirks Obsrvation). Surface hoar is a weak layer that is not to be underestimated. Many avalanche professionals and recreationists alike have been involved in near-misses or accidents, where a layer of buried surface hoar collapsed and propagated an avalanche wider than expected or in a place where it was not known to exist. The signs of instability are not always there, and the potential consequence of a surprise can be severe. 

With the lack of overnight refreeze, todays temperatures forecast to reach well into the 40's and sun at above the valley inversions, wet snow problems could become more likely this afternoon.  Boot penetration that exceeds your boot cuffs is as sign that the snow has lost, or is loosing, cohesion and wet loose problems are increasingly likely.

With the elevated temperatures today, the best skiing and riding conditions will likely be found on non-solar north through east slopes at mid and upper elevations, the same locations you are most likely to encounter the thickest, most reactive and most dangerous slabs. Be heads up today for tell-tale signs of instability such as whoomphs and cracking that extends in front of your skies, although propagation under these conditions can occur without warning. The easiest way to manage the avalanche hazard today is terrain management and slope angle.

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