Banner Summit

Triggering a large, destructive avalanche remains uncomfortably likely today even from long distances away. Sunshine and warm temperatures will cause widespread small wet snow slides that can step down to these deeper weak layers to create large avalanches. Even small wet snow avalanches will be able to gain enough speed, force, and mass to be of consequence. The snowpack is complex and will become increasingly more unstable throughout the day today — build wide safety margins.

From Bad to Worse

Ample sunshine, warm temperatures, and yesterday's rain event are increasing stress and adding complexity to our already weak and unstable snowpack. What was so bad in the first place? Widespread natural avalanches and a cycle of large, remotely triggered slides showed that our thick, meaty slab on top of weak snow from the December drought is likely to break as large and destructive persistent slab avalanches. This massive natural avalanche (photo) ran only a few days ago, breaking across over a mile of terrain and involving 5 separate alpine bowls. Then yesterday we added rain and warm temperatures. Today sunshine and similarly warm temperatures are likely to make things go from bad to worse, and increase avalanche activity throughout the day. The specifics of how fragile snowpacks like ours react to warm, wet, sunny inputs are uncertain, but I can say that it won't be a carefree day in the mountains; not even close. Expect to see a widespread natural wet avalanche cycle on solar slopes. Avalanche problems will change across a  spectrum as you climb through elevation bands. Let's go on a walk uphill to learn what you'll encounter if you choose to head into the hills today:

LOWER: Leaving the car,  you'll find a thin, wet, weak snowpack here. This is the type of snow that could saturate your older skins quite quickly, so don't doddle. Climbing next to steep, snow covered slopes, you'll be able to push small wet snow avalanches. With the direct sunshine, these will already be happening naturally if you get a later start. These slides will start small and pick up speed and momentum as they move downslope. In area where our older, weak snow still is alive and well, these slides may "flank out" as wet slabs, producing even larger, more dangerous avalanches. As you set the skin track, be acutely aware of where you're traveling in relation to even small terrain traps like road cuts, gullies, and creek beds; getting stuffed into a small space by very dense, wet debris will not have a good outcome. 

MIDDLE: Cresting higher, you'll find an even more complex environment here. You'll transition from a warm, wet snowpack into a much colder, drier one. Our wet snow issues remain a prominent concern at the bottom of this elevation band, especially on more solar aspects where the wet snow may run fast and quick on a slick crust. Dry issues will begin to be a concern on the upper end of this terrain, with a concerning mix of both of these issues everywhere inbetween. Avalanches that start as small sluffs up higher in dry snow can run down lower to gain mass from the wet snow, creating a weighty, destructive slide. 

UPPER: You finally arrive on a cold, ice-covered ridgeline with rimed trees. At first glance, 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, the sun will continue to bring fast-running wet loose avalanches to the table. These will be happening naturally during sunny periods and will be easy to trigger. 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.