Storm slabs may be reactive to human triggering, especially in wind loaded areas, and on steep, sun exposed slopes. Watch for signs of instability such as whumphing, cracking and recent avalanches.
Weather Forecast
TUESDAY NIGHT - Cloudy with clear periods and isolated flurries / northwest wind, 10-20 km/h / alpine low temperature near -11WEDNESDAY- Cloudy with sunny periods and isolated flurries / west wind, 10-15 km/h / alpine high temperature near -10THURSDAY - Cloudy with sunny periods / southwest winds 15-30 km/h / alpine high temperature near -8 / freezing level 1300 mFRIDAY - A mix of sun and cloud / southwest winds, 10-25 km/h / alpine high temperature near -6 / freezing level 1500 m
Avalanche Summary
On Tuesday, there were preliminary reports of natural and explosives triggered storm slab avalanches up to size 2.5 in the neighboring Glacier National Park region.On Monday, there were reports of numerous human triggered storm slab avalanches up to size 1.5 and several natural storm slab avalanches up to size 2.5.Reports on Saturday and Sunday include several natural and human triggered storm slab, loose dry and wind slab avalanches to size 1.5. Also on Sunday, was a skier triggered size 2 persistent slab avalanche on a west aspect at 2300m in the northern part of the region as well as a remotely triggered (from a distance) size 3 avalanche on a southwest aspect in the alpine. The second avalanche was in the south part of the region. Both of these were suspected to have run on a layer of facets.There was a report of a remotely triggered size 2 persistent slab avalanche on a north aspect at 2300m in the south of the region on Saturday. It was suspected to have run on a buried layer of facets.
Snowpack Summary
25-50 cm of recent storm snow is sitting mainly on facets (sugary snow), as well as surface hoar (feathery crystals) in sheltered areas and a crust on sun exposed slopes. There are two weak layers of surface hoar in the upper snowpack that were buried in late January and early February. They can be found between 60-120 cm below the surface. These layers consist primarily of surface hoar, though they may be associated with crusts on steeper, south facing slopes. These weak layers are most prominent on south facing slopes and all aspects below treeline. Avalanche activity on these layers has declined in recent days, however it may still be possible to trigger an avalanche in isolated areas such as steep cutblocks, large open glades, and steep south facing terrain.The lower snowpack is generally considered to be strong, except for shallow, rocky areas where the cold temperatures continue to facet (weaken) the snowpack.
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.