Storm slabs may be reactive to human triggering, especially in wind loaded areas and on sun exposed slopes.
Confidence
Moderate - Forecast snowfall amounts are uncertain on Monday
Weather Forecast
SATURDAY NIGHT - Cloudy with clear periods / light northwest wind / alpine low temperature near -12SUNDAY - A mix of sun and cloud / light northwest, switching to light southwest winds / alpine high temperature near -8 / freezing level 1200 mMONDAY - Flurries, 5-10 cm / southwest winds 20-40 km/h / alpine high temperature near -7 / freezing level 1400 mTUESDAY - Flurries, 5-10 cm / light southwest winds / alpine high temperature near -8 / freezing level 1100 m
Avalanche Summary
On Friday, there were reports of natural and human triggered avalanches to size 2, as well as a natural avalanche cycle to size 2.5 in the neighboring Glacier National Park region.On Thursday, there were several reports of human triggered wind slab, storm slab and loose snow avalanches, size 1-1.5, and natural loose and storm slab avalanches up to size 2.5.
Snowpack Summary
15-35 cm of recent storm snow is sitting mainly on wind slabs and 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 40-90 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.