Banner Summit

The snowpack is complex, unstable, and getting wetter by the hour — treat it with respect and build wide safety margins into your travel plans. In the past week, many large human-triggered and natural avalanches were reported, and triggering a large, destructive avalanche remains uncomfortably likely today. Such slides can be triggered from long distances away from steeper slopes (remote triggering). Warm temperatures and periods of sunshine will bring wet snow problems to the table. Smaller natural and human-triggered slides can step down to deeper weak layers in the snowpack, resulting in much larger avalanches. 

Warm, Wet, Weird, Dangerous

Snowpacks react poorly to rapid change. The past month has been one of continual change. We built a hefty slab of snow on top of our exceptionally weak snow from the December drought, resulting in widespread natural avalanches and a cycle of large, remotely triggered slides. We are only a few days out from this massive natural avalanche (photo) that broke across over a mile of terrain and involved 5 separate alpine bowls. And now, we throw rain and warm temperatures at this fragile snowpack. Exactly how the snowpack will react is uncertain, but I can tell you that it won't be pretty. Read on for a run-down of what you'll encounter at different elevations today. 

LOWER: You'll find a thin, wet, weak snowpack here. On steep, snow-covered slopes, you'll be able to push small wet snow avalanches. These may be happening naturally during periods of direct sunshine and rain. These slides will start small and pick up speed and momentum as they move downslope. In areas where our weak snow is well developed, these slides may "flank out" as wet slabs, producing even larger, more dangerous avalanches. Pay close attention to relatively small terrain features like road cuts, gullies, and creek beds; getting stuffed into a small space by very dense, wet debris will not have a good outcome. There is a lot of terrain in the Banner Summit Zone that looks like this, and you can definitely get in trouble there today. 

MIDDLE: There is a lot going on in this elevation band. As you move through it, you'll travel from a warm, wet snowpack into a much colder, drier snowpack. Expect to encounter a range of wet issues at the bottom end of this elevation band, a range of dry issues at the upper end, and a complex mix of both in between. Avalanches that start up higher in dry snow and run down into wet snow down below can become very destructive. 

UPPER: If you grin and bear it through the coastal conditions at lower and middle elevations you'll emerge into a colder, snow and ice covered world. Yes, it is dangerous up here too. At the surface, look for small, recent wind slabs and cornices that may be reactive to your weight. On steep, shaded aspects you may be able to start small, dry loose avalanches involving recent snow. On solar slopes, brief periods of sun will bring wet loose avalanches to the menu. These will be happening naturally during sunny periods and will be easy to trigger. Such slides will pick up speed and run quickly over the crusts underneath. Importantly, all of this activity is taking place on top of an unusually weak snowpack. Avalanches that initiate near the surface can step down to the widespread layers of weak snow buried in our snowpack, producing much larger, potentially unsurvivable avalanches.

Travel through the mountains knowing that you can make large avalanches in many locations. And that the character, location, and size of these slides may surprise you. You may find and trigger avalanches in places where you have never seen them before. You may see slides breaking much wider than you might expect. You may see small, dry and wet snow avalanches become large, destructive wet avalanches as they entrain wet snow on their trip downslope. Head into the mountains expecting the unexpected today. Start with a conservative plan and stick with it.