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
Northwest Inland.
Warm stormy weather will elevate the danger on Monday. Very conservative terrain choices or professional-level training are recommended for any travel in avalanche terrain.
Confidence
Moderate - Due to the number of field observations
Weather Forecast
SUNDAY NIGHT: Storm continues with another 10-15 cm of snow, strong southwest winds, and climbing freezing levels.MONDAY: Another 2-5 cm during the day, strong southwest winds, freezing levels climb to about 1000 m with alpine temperatures around -2 C .TUESDAY: The next pulse brings 5-15 cm starting late Monday night, moderate southwest winds, freezing level dropping with alpine temperatures around -6 C.WENDESDAY: Lingering flurries with 2-5 cm, moderate southwest winds, alpine temperatures around -10 C.
Avalanche Summary
A MIN report from Friday describes a size 1 wind slab avalanche at Hudson Bay Mountain (here). A natural size 2 wind slab was also reported on a northeast aspect in the Howsons.On Monday, the new snow is expected to form reactive storm slabs and has the potential to awake persistent slabs above the weak February interface.
Snowpack Summary
Storm snow totals may reach 20-40 cm by Monday morning with deeper deposits in lee terrain. Rising temperatures will make reactive storms slabs. A weak interface that was buried in late February may finally have enough snow above it to form a reactive slab. The interface is composed of facets, crusts, and surface hoar that may be 40-80 cm deep. There's some uncertainty about the distribution and reactivity of this interface. A well consolidated mid-pack sits above weak basal facets (sugary snow) near the ground. The deeper basal weakness remain a concern in thin rocky start zones and shallow snowpack locations.
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.