Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches possible, human triggered probable.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Regions
Glacier.
We've had a significant amount of snow over the last few days as well as multiple buried weak layers. Approach the backcountry with caution until things have had a chance to settle.
Weather Forecast
Westerly flow will continue to bring unsettled weather to the interior throughout the week. Light snow with generally light west winds are forecast until Tuesday night when more moderate amounts of snow are expected with the arrival of the next storm. Temperatures will remain cool until then.
Snowpack Summary
15cm of low density snow overnight sits over settling storm snow. The Mar 13 crust is down ~50cm on solar aspects and below 1600m. The Mar 2 crust is down around 1m-1.25m and the Feb 10 surface hoar/crust layer is down 1.5m-2m. The mid and lower snowpack is very well settled.
Avalanche Summary
Natural avalanche cycle yesterday and artillery control produced avalanches to size 4.0 with numerous size 3-3.5 within the highway corridor. From March 13th, skiers remotely triggered this avalanche on Grizzly peak. Note the shallow, south facing start zone. It ran presumably on the March 2nd crust.
Confidence
Due to the number of field observations
Problems
Storm Slabs
Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.
Persistent Slabs
Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.
Deep Persistent Slabs
Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.
