Banner Summit

Your main concern today is triggering a large avalanche that breaks widely on buried weak layers. While the likelihood of this is gradually decreasing, it is still a worrisome possibility. Don't expect any signs of instability before triggering an unsurvivable slide. These avalanches can be triggered from long distances away and run into terrain far below. Dense, freshly formed wind drifts will be sensitive to your weight in steep, upper elevation terrain. 

With over a foot of fresh snow falling by this evening in this zone and sustained moderate winds, you will not be able to ignore new snow issues as you climb higher in terrain today. Dense deposits of wind-drifted snow will become larger throughout the day, and if the winds shift to the north earlier than forecasted, there will be even more snow available for transport. Even when small, these slabs as well as loose snow sluffs can have severe consequences if they knock you off your feet in the wrong terrain and send you skyrocketing head first into the landscape. With cornices already present in upper elevation terrain around Banner and in the nearby Sawtooths (see photo), these large features can grow past their breaking points today and start to fail. All of these new snow issues can serve as triggers for the persistent slab dragon that lurks deep below...

In the past three days in different forecast zones, skiers remotely triggered a large avalanche and a separate group got a collapse that traveled over 1000' on their third lap up a skin track. The weak layers in this zone are deeper and harder to impact, however the theme slides you can trigger here remains the same.

Navigating MODERATE Avalanche Danger with our widespread persistent slab problem is no walk in the park. There is no golden rule, or set of rules, that will give you the green light to ski a slope. We can give ourselves broad brushstrokes of terrain characteristics as aids for picking slopes that are less likely to slide and that have less severe consequences. Slopes where you are most likely to trigger these slides are going to be wind-loaded, thin, rocky, alpine terrain with steep rollovers. Terrain where you're less likely to trigger an avalanche and consequences will be lower are going to be evenly covered, with clean runouts that have no terrain traps at the bottom (trees, rocks, cliffs to be strained through). With this being said, these are not rules but trends. 

To move through the mountains is to accept uncertainty — we can never control every aspect of a day. Terrain selection is how we get to pick how much uncertainty we accept. While MODERATE Avalanche Danger means that there are many slopes of avalanche terrain you can ski and not trigger a slide, the chance of triggering a large, unsurvivable slide remains. As a mentor, and fellow forecaster who passed away last week told me on my first day out in the field with him: "We study layers and grains, collect observations, and think that we know. But you can't know. And neither can I. We're always playing a game of odds." He reminded me of this throughout the season, asking me, "Do you really know that?" many times while still enjoying many days of great skiing in avalanche terrain. Try to remind yourself of this as you're moving through the mountains. If you choose to enter avalanche terrain, you can use your terrain selection to stack those odds in your favor.