Banner Summit

Large avalanches are unlikely today. You may find small, isolated wind drifts on the highest exposed ridgelines. If the sun comes out, small natural and human-triggered wet loose slides will become possible on slopes directly facing the sun.

USE NORMAL CAUTION: The snowpack in the Banner Summit zone is generally stable and there is no clearly defined avalanche problem. While unlikely, you may be able to trigger small wind slabs in exposed, upper elevation terrain. This problem will be most pronounced on NE-N-NW facing slopes, and the slabs might be resting on a weak crust-facet combination. Look out for smooth, pillows of snow close to ridgelines, and avoid them when you find them. If the sun comes out, wet loose avalanches will be possible on steep, rocky terrain directly facing the sun.

Looking back at these last couple of months, I probably don’t have to remind you that February and the first half of March were all about clear skies and sunshine. This dry spell created weak, faceted snow surfaces, especially where the wind or sun could not get to the snow. Nowhere was this dry spell stronger than in the Pioneers and the mountains around the Wood River Valley, and it got to the point where, in many areas, the snowpack was completely rotten and faceted top to bottom. 

When snow finally returned, it did so favoring precisely this southeastern part of the forecasting area. Adding the biggest load to the weakest snow resulted in some big avalanches (link to Bens North Fk picture) around the North Fork of the Bigwood River and in the Pioneers. 

Further north, in the mountains around Galena Summit, weak surfaces—while still common—were less widespread. This area also received less snow when the taps turned back on. As a consequence, avalanche activity has been more spotty, with smaller, shallower slides. 

This pattern continues as we move north of the pass and into the Sawtooths. A less severe drought, less precipitation in the latest storms and little to no slab avalanches. As you might guess by now, the Banner Summit Zone too follows this pattern, and wind slabs on weak crust-facet combination—while not possible to rule out completely—are few and far between.

So what does this mean moving forward? It looks like we might have more moisture on tap in the coming week, and if this turns out to be true, we will start seeing more buried weak surfaces becoming “active”. The further north we go, the more snow and wind will be required for this to happen, and the problem is unlikely to be widespread.